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How-to: Dodge Ram AAM 11.5" Axle Rebuild with New Ring & Pinion Gears

11.5 AAM axle with new 4.56:1 ring-and-pinion gears

American Axle & Manufacturing ("AAM") builds OEM axles for Chevrolet and GMC trucks and Dodge Ram. The magazine's own '05 Ram 3500 4WD came with an AAM 11.5" rear axle and an AAM 9.25" front axle. This article is the change to a 4.56:1 axle ratio and applies to both GM and Dodge Ram AAM 11.5" axle assemblies. Differentials and brake assemblies may vary; however, overall axle and differential service procedures remain largely the same. Use a model-specific shop manual as a reference guide.

The bump to 35" diameter tires left our Dodge Ram 3500's original 3.73:1 axle gears lacking. Too tall gearing for the new BFG tires, plus an added 1,100 pounds of utility accessories during the Ram's "makeover", the truck needed remedy. Boosting engine power was a possible solution. A change to 4.56:1 ring-and-pinion sets made better sense for our planned trailer pulling.

Our choice: Superior Axle & Gear'

     AAM axle gearsets are available from several sources. For quality components, we turned to Superior Axle & Gear for reliability and a "kit" approach. The package consisted of two ring-and-pinion matching sets (11.5" for the rear, 9.25" for the front) plus Timken bearing sets, new ring gear bolts, preload shims, crush sleeves, seals, sealants, thread locker, tooth contact paint, and a pinion nut for each set—complete!

     For those familiar with Dana integral axles, the AAM approach is a departure, especially the differential carrier removal and installation. In some ways, the AAM is quicker to set up than the Dana units. However, like every axle type, the critical, adjustments remain the same and in this sequence: 1) pinion depth into the housing, 2) pinion bearing preload, 3) differential/ring gear backlash, and 4) carrier bearing preload.

Preload adjuster nuts require either a Miller 8883A spanner or a tool like this one, fashioned to serve the same purpose.

     The right tools are an important part of an axle builds. The AAM units require some specialty tools. In this step-by-step coverage of the ring-and-pinion gearset change, tools play an important part. Some tools are inexpensive, others can be improvised—a few will require willingness to invest in tooling.

     From this how-to coverage, determine whether rebuildng your own axles matches your skill level and tool budget. Whether this is a one-time task or your professional work, the steps described will serve as a guide for these critical tasks.

Skill level required: Familiarity with gear mechanisms and ability to follow technical steps.

Needed tooling: Specialty tools required—review the steps before taking on this kind of project.

Use wheel chocks to secure opposite axle from rolling.

Step 1: Use wheel chocks to prevent vehicle from rolling! Once jacked up on a slope, the vehicle will roll whether in Park, gear or even with the E-brake set.

Use safety stands rated for your vehicle.

Step 2: Always use a quality set of jack stands and a rated floor jack. Our Dodge Ram 3500 is now over 8900 pounds curb weight. These Walker stands rate 5-tons apiece. Pittsburgh floor jack rating is 4-tons. Both work well and provide a safety margin.

Both stands rate 10-tons and readily support the Ram 3500 4WD.

Step 3: At 5-tons apiece, the load capacity of these two stands is 10-tons. Note placement at base of axle tubes, between spring U-bolts, away from brake tubing. Tires are just off the ground and can be removed readily.

Full-floating rear axle makes job much easier.

Step 4: Ram 3500 has a full-floating rear axle. This makes differential work much easier. Axle shafts are quickly removable, rotors and calipers can stay in place.

Draining axle oil into pan

Step 5: Drain the axle oil into a clean pan. Inspect for metal and debris. You will wipe out the differential cavity with clean, lint-free rags. Properly maintained oil on the Ram 3500 is clean and free of contaminants.

AAM 11.5

Step 6: OEM 3.73 gears worked for 100K miles just fine—right up to the switch to 35" diameter tires, a 3-inch diameter increase. 4.10:1 would be a direct correction for the tire size increase. 4.56:1 meets plans for trailer pulling—plus the added weight of accessories and auxiliary fuel.

4.56:1 axle gearing for the Ram 3500 4WD with Cummins

Step 7: Superior Axle & Gear's 4.56:1 ring-and-pinion gearset is a precise, durable design. We selected 4.56:1 based on research from Cummins and our trailering needs. With 35" tires, 4.10:1 is the direct equivalent to the OEM 3.73 gearing with the original 31.9" tires.

  Note: If you have bigger diameter tires in mind and are pleased with your truck's performance with the stock size tires, simply restore the ratio and offset the speedometer error. For our Ram 3500, a 3.73 to 4.10 change would accomplish this...We went a step further to meet heavier towing needs.

   Footnote: The 4.56:1 gears require a speedometer correction. Also, the engine now operates at higher cruise speed (actually closer to Cummins' own rpm recommendations for the ISB diesel engines). Be prudent here, especially with a diesel engine. Unless you have a distinct need for lower (numerically higher) axle gearing, don't go any lower (numerically higher) than a restorative ratio!

To learn more about how we made our gear ratio choice, click here!

Removing full-floating rear axle shafts.

Step 8: Full-floating rear axle shafts are easy to remove: begin by removing the eight flange bolts. Unless there is a threaded relief hole, use a wedge-shaped, broad chisel to separate the axle shaft flange from the hub.

Caution: Do not damage the metal! You are merely spreading these parts at the gasket, not chiseling or nicking metal.

Axle shaft removed

Step 9: Axle shaft removed, the hub, spindle and wheel bearings are visible. Note that there is no mark where the chisel separated the axle shaft from the hub. Axle shaft and hub have been indexed with yellow metal marker for alignment at reassembly time.

Full-floating axles

Step 10: Virtues of full-floating axle are clear. Vehicle will actually roll with shafts removed. (Note: Oil will leak out!) This is a distinct safety advantage over a semi-floating axle. Time-honored, heavier duty truck design provides ease of service. Differential assembly can now be removed.

Spring locks for the preload spanner nuts

Step 11: Spring locks keep the differential bearing preload nuts from rotating. Remove these bolts and springs to make adjustments or remove the differential...

Spring clip at opposite side

Step 12: Loosen opposite retainer bolt and spring lock. Note the relationship of these parts for reassembly.

Rotating and loosening the preload adjuster nuts

Step 13: Bearing caps are machined match for the axle housing saddles. To maintain precise fit, you must install caps in correct position—with the caps facing the right way! Here, one light pin mark at the left cap and housing indicate the cap alignment for the left bearing cap.

Right bearing cap identification marks

Step 14: Right bearing cap gets two pin marks. Note that the marks should indicate which side and how the cap faces top-to-bottom. Axle housing gets a matching pair of pin marks.

 Loosen the bearing cap bolts

Step 15: Bearing caps marked, you can now loosen the bearing cap bolts. Do not remove bolts until you can safely support the heavy differential carrier and ring gear!

Removing bearing caps

Step 16: Remove bearing cap bolts. Rock cap slightly to loosen if necessary. Do not distort the cap or mar the cap-to-housing. This is a precise, machined fit. Protect the caps.

Caution: As a precaution, leave bearing caps in place if the adjusters do not securely hold the differential in place! Badly worn bearings or mis-adjusted spanner nuts can allow the differential to roll out of the housing once the caps are removed! 

Warning: The 11.5" differential carrier and ring gear are heavy and can cause severe physical injury if not supported during removal!

Caps removed, adjusters exposed.

Step 17: In this case, the bearing adjusters were tight with preload. Do not allow the differential to roll out of the housing. Leave bearing caps in place with bolts "finger tight", loose enough to permit backing off the adjusters. To avoid parts damage, do not let the toothed toner ring drop onto the housing.

Spanner nut adjusters for bearing preload 

Step 18: Right side spanner nut is still tight. The marring of the holes is actually "factory"; the axle has never been apart. While some use a punch with a blunt, rounded nose end to tap the adjuster rings loose, there is a factory service tool for the task. (See below.)

Miller-SPX tool #8883A 

Fabricated spanner nut tool

Step 19: At top is Miller-SPX #8883A Tool, the official tool for the adjuster nuts on AAM 9.25", 10.5" and 11.5" Chrysler, Dodge and Ram axles. Bottom is our "homemade" tool. (See details on fabricating a tool like this one.) If you want to do this job correctly, consider purchasing the Miller tool or the equivalent tool for GM axles.

The Preload Adjuster Nut Dilemma

  The Miller-SPX #8883A Tool is available at the SPX website. Note cautions on the tool like "Do not use for removal". Miller-SPX tool is high quality and well designed for this difficult application—as you will quickly discover.

  AAM's 11.5" axle design creates decreasing notch exposure as the adjuster rings thread into the axle housing. This requires a thinner tool, one not capable of handling excessive force. If the AAM axle adjuster notches were fully exposed over the range of adjustment, a thicker, stronger tool design would be possible.

  Our Ram 3500 AAM 11.5" differential preload nuts did loosen within the torque limits for this tool. There are occasions, however, when an overly tight nut adjustment, binding spanner nuts or axle exposure to heat can increase the torque resistance...Use prudence here!

  Footnote: In a phone call to the Miller-SPX tech line, tech staff acknowledged the challenges of this spanner nut design. The alloy steel SPX tool will take considerable load before its small notch tab fails. As a precaution, the staff suggested the use of a blunt, rounded end punch and hammer to break initial torque on an overly tight adjuster nut. Your call...If you do use a punch, do not damage the adjuster rings! Vacuum away any metal debris from the axle cavity and all gear parts.

Carefully remove the differential assembly.

Step 20: Bearing adjusters are right-hand thread and loosen into the axle housing. Fine housing threads must be handled carefully. Back off adjusters carefully and be ready to catch a heavy 11.5" ring gear and differential assembly!

  Caution: A support platform—like a transmission jack—is helpful...Support the differential assembly to prevent damaging the tone ring teeth. A block of wood beneath the tone ring will prevent teeth from dragging or banging against the axle housing as you roll the differential assembly from the bearing saddles. Avoid pinching or crushing your fingers. If an assistant is nearby, ask for help!

Differential/ring gear assembly on the floor.

Step 21: Big enough? 9.25" is more like a Dana 44 or AMC Model 20 unit. This is the 11.5" that can tow a nine-horse trailer and handle dual wheels and a diesel engine! 

  Caution: To avoid severe injury, don't get pinned beneath this differential and ring gear assembly. Use a transmission jack—and strap the safety chain, too!

Pinion shaft and gear remain in place.

Step 22: The 3.73:1 pinion gear remains in place. Mark and remove the threaded bearing adjusters. You will want to clean and oil them to assure smooth adjustment during differential installation.

Bearing adjuster and cup saddle

Step 23: Bearing cups fit precisely into the housing saddles. Adjusters thread into the axle housing at each side. These parts must be clean for proper fit and accurate adjustments.

Remove adjuster with round tool.

Step 24: Mark the adjusters with pin punch for proper location on reassembly. You can use this tapered tool to loosen the adjuster ring from the axle housing. The rings should rotate freely if threads are not damaged.

Ring gear removal from differential case

Step 25: Loosen and remove all ring gear bolts. These bolts may be extremely tight due to factory thread locker (equivalent to Loctite 271 High Strength red). A high-torque air wrench and moderate heat (500 degrees F maximum) may be required to loosen these bolts.

Separating ring gear from carrier

Step 26: Unless there is an issue, the ring gear can be removed by tapping four loosened bolts at opposite positions on the carrier. Light taps in sequence will prevent the gear from binding on the carrier. Do not strike or damage the carrier casting!

  Note: Presumably, the ring gear and bolts will be replaced. If reusing the ring gear, use caution: Do not damage the threads. Tap with a brass punch at the beveled edge of the gear.

Ring gear removed

Step 27: Ring gear dropped off uniformly and quickly. Note the factory sealant, powdered on the gear threads. This created strong resistance when removing the bolts. Tone ring can stay in place. Leave the tone ring-to-carrier screws tight.

Observe original gear tooth pattern

Step 28: Observe the original tooth contact pattern. This OEM 3.73 ring gear worked just fine and shows a distinct and correct tooth contact. If correct, try to emulate a similar pattern on your installation.

Disconnect driveline

Step 29: Rear driveshaft can now be loosened. Mark the pinion flange-to-U-joint flange for reassembly. Drivelines are often balanced as a full assembly. In any case, if there were no signs of imbalance, indexing will prevent an issue.

  Note: Flange design and pinion seal I.D. can vary between applications. This is the Dodge Ram approach and parts orientation. Make sure the new replacement seal and parts are for your axle type and vehicle model application.

Unbolt driveshaft yoke flange

Step 30: Four bolts removed, the driveshaft is carefully set to the side or wire-tied out of the way. On a one-piece shaft like the 140.5" wheelbase Ram 3500, keep the slip yoke in place at the transmission or transfer case. This will prevent oil from leaking out and save time during reassembly. Protect the transfer case or transmission output seal.

Use of yoke holding fixture 

Step 31: Use of a yoke-holding tool and air impact wrench is the safest way to remove the pinion nut. Used properly, an air wrench is far less risky than a long breaker bar, socket and muscling the nut by hand.

Note: The other end of the yoke holder rests firmly against the floor in this project. Know which direction the yoke tool rotates before applying force to the pinion nut!

Pinion nut removed

Step 32: Yoke holds pinion flange securely, and nut comes loose readily with high force impact. You should use an impact-rated socket for this task. The 12-point socket size is 36mm on AAM 11.5" Chrysler applications. A quality impact socket can get expensive in this size 12-point. Safety is at stake.

Removing the pinion shaft from the front bearing

Step 33: Sometimes, especially on lighter axle applications, the pinion shaft can be "danced" carefully through the flange and front bearing with an air impact driver.

Caution: Use a tapered, blunt or round-end tool, not a chisel point! Impact force will cause less trauma than "tapping" on the pinion shaft's end after the splines have been coated with factory Teflon paste.

Using a puller on the yoke flange

Step 34: The flange was so stuck with Teflon paste that a puller was necessary to remove the flange. Advance Adapters has a great tool for this task on axles with saddle-type yokes or smaller flange patterns than the 11.5" AAM flange on the Ram. Splines are not tapered, the resistance here is from the paste—which took considerable force to overcome!

Teflon paste on yoke flange splines

Step 35: This paste is more like cement after 110K miles of driving! Cleaning takes solvent and time with a brush. Inspect for nicks or a seal lip groove. Polish the seal riding surface.

Teflon on the pinion shaft splines

Step 36: Paste is evident on the splines of the pinion shaft. This is all with good intentions, to prevent gear oil from wicking out the shaft splines in service. Years past, Permatex 300D Gasket Sealer worked just fine for this task. Loctite Superflex RTV, provided by Superior Axle & Gear, was our reassembly choice...OEM calls for Teflon paste (like Loctite 592 PST). Your choice.

Pinion held in place by front bearing

Step 37: At this point, the pinion gear remains in place because the front/flange end bearing is a press fit onto the pinion shaft. The pinion shaft gets "tapped" through the front bearing, which will be replaced with a new bearing cone and cup.

Pinion shaft out of housing

Step 38: Not intended for reuse, this shaft was "tapped" through the front bearing with considerable persuasion. During assembly, the front bearing is a press fit onto the flange-end of the pinion shaft.

Pinion seal removal

Step 39: An attempt with a curved pry tool failed, and this works as well. Make sure your chisel point is sharp, tapered long and narrow. Catch the seal edge without gouging the axle housing casting. Work the seal inward and out, avoiding force against the iron casting. The seal came out in a minute, less time than rumaging for the specialty seal puller in the tool box.

Seal out and bearing removed

Step 40: Seal out, the loose bearing cone comes right out. You should now replace the bearing cups (shown) and cones. Note that there are no marks on the housing from the seal removal with the chisel.

Using a punch to remove bearing cups

Step 41: Despite available specialty pullers, a quick and effective way to remove bearing cups is via a hefty tapered punch with squared end. There are reliefs at 180-degree points in the housing. The flat punch end can safely catch the shoulder of the cup.

Caution: Tap back and forth between the two relief points, carefully and uniformly, to prevent binding the bearing cup or damaging the housing bore! Wear eye protection, the punch and bearing steel is very hard.

Big inner bearing cup removed

Step 42: Inner, gear head bearing cup is now removed. Bore is unmarked, not blemished in any way. Use care and the two relief points for the blunt-end punch.

Same approach for front bearing 

Step 43: Again, the tapered punch works well on the bearing cup at the pinion flange or nose end of the housing. This is a smaller cup. Stay on the bearing cup edge and avoid damaging the axle casting. Tap side to side, 180-degrees apart.

Bearing spreader on carrier bearings

Step 44: A quality bearing spreader will lift the carrier bearings from their seats without damaging the crown or flanges of the differential carrier. Do not squeeze the spreader to the point of interfering with the differential flange.

Three jaw bearing puller 

Step 45: Using an adapter within the border of the carrier flange, this three jaw puller gradually works the bearing loose. A puller of this kind has no means for holding the jaws inward. The better tool of choice here would be a Posi Lock™ puller!

Bearing coming loose

Step 46: Though tedious and requiring considerable caution, this puller does remove the bearing. See how much more effectively the Posi Lock™ puller does this task (below).

Posi-Lock gear and bearing puller

Step 47: This is the Posi Lock™ gear and bearing remover. The Model 208 shown will also accept optional transmission front bearing jaws for pulling via the bearing's snap-ring groove! Force for this tool is 12-tons, with the side clamp preventing jaws from spreading under this force.

Posi-Lock removing carrier bearing

Step 48: With an adapter on the carrier flange end, the Posi Lock grips the base of the bearing. If jaws are narrow enough, they will fit the two notches in the carrier case. Here, the bearing spreader has lifted the bearing cone high enough for the Posi Lock's jaws to safely grip the bottom of the bearing's inner race collar.

Old pinion inner bearing removal

Step 49: Original pinion shaft bearing is removed to access the pinion depth shim. This is a crucial reference if you are not setting up the pinion depth from scratch with discs, arbor, a pinion block, "scooter" and dial indicator.

Note: "Factory" method for setting pinion depth is now the full pinion depth gauge apparatus. This is a definite for a new, blank axle housing. On a used or properly functioning axle, it is just as practical to use the method described here, with dummy trial bearings and tooth contact tests—about as quick, too, since we always run tooth contact tests, regardless of the pinion setting method!

Towers support the bearing spreader

Step 50: Angle steel towers with flat platforms on top support the bearing spreader squarely. Towers offer a place for the large pinion gear to drop. Press applies pressure to old pinion shaft's end, forcing the bearing off the shaft.

OEM pinion depth shim

Step 51: The original pinion depth shim is 0.054" thick and numbered so. This is a baseline for setting depth. Adjustment of shim thickness will depend up the tooth contact pattern results. We will start with an 0.054" shim stack built with new shims provided in the Superior Axle & Gear kit.

Note: On these AAM axles, there are no +/- marks with thousandths of an inch "pinion variance" indicated. That was once a reliable means for setting pinion depth on an axle—at least a starting point. See the "dummy bearing" procedure described below and throughout the magazine. This makes pinion depth setup much simpler and quicker if you do not have a pinion depth gauge fixture and specialty tools.

Building a shim stack

Step 52: Superior Axle & Gear's installation kit includes new shims for the pinion depth. (Original shim shown here.) A crush sleeve eliminates the need for shimming the pinion bearings to set pinion preload. The crush sleeve is a big time saver!

Assembly lubrication

Step 53: LubeGard, a high lubricity, thin assembly oil, works for us. Unlike the OEM recommendation of gear lube, this oil reduces friction dramatically and is not temperature or pour sensitive at shop and reasonable outdoor temps. LubeGard also helps prevent galling of bearings and machined surfaces during assembly. A light coating does the trick...Your choice.

Adapter collar to protect the carrier flange

Step 54: When pressing on new bearings, make sure the bearing rollers and cage are not binding or getting squeezed in any way. Check rotation constantly. Here, an adapter rides on the inner bearing collar as the bearing presses onto the flange. LubeGard prevents galling and bind. Press squarely!

Air-hydraulic press

Step 55: This inexpensive, bottle-jack 20-ton press frame gets a lift from a 20-ton air-over-hydraulic jack. The jack can work with compressed air or by hand (hydraulically). Yes, there are expensive presses tailored for this work. This one works fine for less frequent use. A dial pressure gauge would be a practical accessory.

Adapter for bearing press

Step 56: Step driver tool serves as a press tool here. The aim is to avoid any pressure on the bearing cage. The tool must also clear the carrier flange. Watch how this works...

Side view of press work

Step 57: The tool rides inboard of the bearing cage and outboard of the carrier flange. Pressure is against the inner collar (race) of the bearing...

Tool inside the bearing cage

Step 58: This tool also clears the differential carrier flange at the inside diameter of the driver...

Bearing in position

Step 59: The inside step of the tool allows the bearing to end up below the lip of the carrier flange. (Tool must clear the lip.) Make sure that the bearing seats completely. If necessary, improvise this tool with pipe. Protect both the bearing and flange.

Heat ring gear for installation

Step 60: Warming up the ring gear makes installation easier. Using our parts washing cabinet heated at 145 to 150 degrees F, the gear goes for a 10-minute wash and winds up uniformly saturated with heat. Use protective leather gloves to set the gear in place—quickly, while uniformly hot. Make sure the bolt holes align as you set the gear on the carrier flange. Use pilot studs* if necessary.

*Pilot studs are simply long bolts of the same diameter and thread pitch as the ring gear bolt holes. Cut the heads off, and if you want to be "creative", file a screwdriver slot at the end of each stud. Two studs, placed 180-degrees apart, can act as a guide for the ring gear. Once the gear drops in place, unthread the long studs from the ring gear threads.

  Caution: Do not use a torch to heat the ring gear! The temperature described here is plenty; this is alloy steel and not a candidate for much expansion. Too much heat also risks damaging the gear's case hardening—and you don't want that to happen! 

Installing ring gear bolts   

Step 61: Make sure ring gear bolts have thread locker. (New bolts from Superior Axle & Gear have OEM type thread locker already on the threads.) Red Loctite 271 is high strength needed for this application. Tighten bolts a few threads at a time in cross, uniformly, and gradually come up squarely to torque setting. Do not cock or bind the gear on the flange, make sure the gear remains square with the flange.

Red Loctite 271 or 27100

Step 62: Do not waste time with Loctite 271 in place. Use as prescribed, and get ready to torque hardware to specification. 11.5" AAM axle ring gear bolts take 175 ft. lbs. torque by OEM recommendation. Bring torque to specification in gradual steps.

Note: Not only does Loctite 271 help prevent bolt loosening, it also helps maintain original torque settings as the load on the ring gear tugs at hardware over time.

Setting torque on ring gear bolts

Step 63: This accurate 0-250 ft. lbs. torque wrench makes several trips in cross, gradually increasing torque (75, 100, 150, 175, again at 175). Let bolts set for five minutes after final torque is reached, then do the entire set at 175 ft. lbs. again. If you need to brace the assembly, use safe anchor points and do not damage parts!

Caution: There are errors in torque setting recommendations in the Dodge Ram OEM shop manuals. Figures offered here were compared to G.M. and other sources to determine the "correct" settings for the 11.5" AAM rear axle.

Making dummy or trial fit bearings 

Step 64: For setting pinion depth, a trial fit can be quickly made with the use of dummy bearings. If the original bearings are in reasonably good condition, carefully rout out the inside diameter of the bearing cones, just enough to finger-press fit the bearing onto the pinion shaft. Used bearing and shaft measurements will be very close to the new pinion shaft and new bearings.

Footnote: For axles without crush sleeves, make dummy bearing cups and cones for trial fit. Remove a slight amount of material from the outer edge of old pinion bearing cups, just enough to finger press the cups into the axle housing bores for trial shimming and testing. When the preload is correct, you can install new cups in the housing and press bearing cones in place. Use the correct shim stack thicknesses, as determined during the trial testing.

Rout out the bearing inside diameter slightly

Step 65: Inexpensive drum sander arbor and course sanding discs can remove the slight amount of bearing steel from the inner bore. Bearings are hard, so use gritty abrasive to save time. Sand evenly to keep the bearing bore round. Continually trial fit the bearing to the shaft. You want just enough sizing to permit the bearing to fit on and off the shaft squarely, using hand force.

Bearing is now a hand press fit onto shaft.

Step 66: These original bearings were both fitted to the shaft by hand. There is no looseness to the fit, round and sized enough to slide onto the shaft. Clean the bearings thoroughly and oil with light assembly lube.

Bearing and trial shims

Step 67: Now the dummy bearing fits to the new pinion shaft/gear. A stack of shims is at the OEM thickness for the first depth check. The bearing slides snugly onto the shaft and will come off with hand force. This serves as a quick trial fit tool.

Installing new bearing cups in axle housing

Step 68: A cup driver tool installs the new inner bearing cup. This cup will be seated squarely and oiled lightly for trial fit. Again, LubeGard works well to reduce friction and provides an accurate depth measurement and bearing preload.

Seated and oiled inner cup

Step 69: Cup squarely in place and seated. Bearing cups must bottom in clean bores and fit tightly, without galling or any interference from debris. For accurate pinion depth and bearing preload settings, cups must fit properly. Confirm seating from other side.

Bearing cup driving tool

Step 70: This is a professional grade, OEM type bearing cup driver tool. It fits the bearing cup's taper and has a strong shoulder for squarely driving the cup edge. The cup must be driven straight, not bind or gall, entering its bore squarely.

Front bearing installation 

Step 71: Clean, prepped bore prior to installng the front pinion bearing cup. This smaller bearing cup, if driven squarely, will enter the bore without trouble.

Cup in place

Step 72: Note that bearing cup seats squarely. Look at the bearing seat edges from the opposite side. Be sure the cup seats all the way and snugly. This assures proper preload settings.

Bearing cups ready for pinion depth checks

Step 73: New bearing cups squarely seated, pinion depth trial fit can start. The new pinion shaft will use the dummy bearings and a 0.054" shim stack in this case. (Use your original pinion shim thickness for the first trial test.)

New pinion shaft in place with dummy bearings

Step 74: New pinion shaft fits through the dummy front bearing. The dummy bearings fit with the first trial stack of shims. Preload adjusters are oiled lightly and threaded into the axle housing at each side. Adjusters must turn freely, without drag or notchiness.

Quick fit for pinion flange

 Step 75: For trial fit, the pinion seal is left out, and so is the crush sleeve. Grind the crushed section off the old pinion nut, enabling it to thread on and off the pinion shaft easily. This saves time and gives a quick read of pinion depth and the gear tooth contact pattern. For now, tighten the nut to either the factory preload setting or zero play plus "light" rotating resistance.

Transmisson jack to move the differential assembly around 

 Step 76: Consider using a transmission jack for the 11.5" AAM differential carrier. This assembly is heavy! Here, a transmission adapter on a floor jack works well.

Carrier in position for first test

Step 77: The differential carrier goes into position. Bearing cap bolts can be tightened with a box end wrench by hand at this stage, then backed off 1/4 turn or so to enable smooth rotation of the side adjuster nuts.

Quick tooth contact pattern check

Step 78: A quick check of tooth contact pattern can be done with a short stretch of painted teeth. This is the yellow marking compound furnished with the Superior Axle & Gear installation kit.

Looking at the pinion depth

Step 79: Set backlash close for this check, a barely perceptible rock of the ring gear. Set a light load on the carrier bearings, using the spanner tool. This will center the differential for an accurate read of pinion depth with bearing cap bolts snug.

Note: Right away, it is clear that the pinion is not reaching into the ring gear teeth deeply enough. Pinion gear rides high on the drive side of the ring gear teeth.

Coast side look at tooth contact

Step 80: Coast side also shows high-riding contact. Note how the print is somewhat centered but high toward the "crown" or top ridges of the teeth. Mesh can go deeper toward the "flank" or "root" of the teeth. This requires moving the pinion higher, more toward the differential/axle shaft centerline.


Modern Tooth Contact Patterns and Gear Cut Types

(   Courtesy of American Axle & Manufacturing)


     Tooth height is measured from the root (bottom of tooth) to the crown (top of tooth).

     The two-cut tooth is the same height at the toe (inside of gear) as it is at the heel (outside of gear). The two- cut gear set has a natural "bias" condition; that is, the pattern shows up slanted when the pattern is rolled with gear marking compound.

Two-cut tooth pattern


     The five-cut tooth height is shorter at the toe (inside of gear) and is taller at the heel (outside of gear). The five-cut gear set appears as a square pattern when the set is rolled with gear marking compound.

Five-cut tooth pattern


Out comes the differential assembly

Step 81: To roll the differential out without risk of damaging the tone ring teeth, use a block of wood beneath the tone ring. The jack platform is able to catch the weight and allow handling by one person if necessary. Do not bang these parts up!

Added shim tests

Step 82: Much better! Even without full pressure or drag on the ring gear, it is clear that the pattern is both centered properly and below the ridge of the teeth faces (crowns). This is actually the second re-test. 0.057" was not enough, and the pinion head has been raised to 0.059" in this case.

Coast pattern good

Step 83: Nice coast pattern, too! Spread across the tooth, below the face/crown, and not too deep into the root or flank. This is with some resistance created at the pinion flange to press and spread the yellow marking compound, making the impression more representative of load.

Loosening bearing preload

Step 84: To remove the differential and install a new bearing on the pinion shaft, the adjusters must be backed off. With cap bolts slightly loose, the adjusters are moved with a round, narrow tool like this Torx driver.

Note: The Miller-SPX 8883A spanner will only loosen these adjusters so far. Adjuster holes "disappear" into the housing, becoming narrow slits.

New shim stack for pinion depth

Step 85: Stack of 0.059" shims is fitted onto the pinion shaft. New inner bearing gets pressed into place. Make sure the bearing is not bound, that the pressure is against the bearing's inner collar only. Any pressure outboard of the collar can damage the bearing cage, rollers or contact surfaces.

Note: 0.059" is correct for this installation. This is not a "universal" truth, and each axle is different for both the OEM shim thickness and the correct shimming for the new pinion gear. The difference in this case is 0.005", which also varies between installations. Look for your axle's correct tooth contact pattern.

Installing new pinion bearing with shims

Step 86: Bearing gets pressed into position. There is support from below on the inner bearing collar. Old race is strictly to keep the rollers and cage in position. Force is against the inner bearing collar.

Bearing in place

Step 87: Keep shims centered until the bearing (inner collar) seats completely, with some pressure. You want compression of the shim stack. The new crush sleeve is in position. 

Note: This crush sleeve must be in place when you insert the pinion shaft through the new front bearing and seal.

Front pinion bearing in position

Step 88: Rear axle accepts the new front or flange end bearing cone. Make certain that you install the crush sleeve on the pinion shaft before running the shaft through this bearing. You can install the new seal first; this will help keep the bearing in place.

Permatex Superflex RTV sealant

Step 89: Superior Axle & Gear provides a tube of Loctite 'Superflex' blue RTV sealant in the installation kit. This is great stuff! A thin coating on the seal jacket or edge backs up the neoprene seal. Use sealants sparingly. An even, uniform coating will do.

  Note: Dodge Ram and GM applications use different yoke flange types and seal I.D. sizes. Make sure you have the correct pinion seal for your application before installing the pinion shaft and flange!

Installing the pinion flange seal

Step 90: With a tool chest draw full of seal drivers, this approach works just as well. Tap evenly and prudently around the seal flange edge. Do not bend the seal flange edge. Make sure the seal goes into the bore squarely.

Seal installed properly

Step 91: Seal installed properly, square and evenly seated on the flat nose of the casting. Grease is inside seal lip. Spread grease evenly to lube the pinion sealing joint. Make sure the pinion flange's sealing surface is clean. Polish with fine crocus cloth or 3M Scotch Brite pad if necessary. Remove debris.

Loctite Superflex RTV

Step 92: Careful application of sealant can reduce risk of any oil seepage. The Loctite Superflex works well, applied to the splines and the inside face of the flange. When the flange is installed, this mating face will seal against the bearing inner collar. Oil wicking is prevented by using correct sealants.

Note: OEM manuals recommend Teflon paste on these splines. You can do that if desired. This install opted for Loctite Superflex Blue RTV. Loctite 592 PST Thread Sealant would match OEM material.

Pinion flange installation

Step 93: Wipe off excess sealant before installing the flange on a clean, dry pinion shaft. Make sure the new crush sleeve is in place. Keep the pinion shaft on-center. Run the pinion shaft's threaded end through the bearing while centering the flange with the pinion seal. Keeping on center, bring these parts toward each other. Do not distort the seal lip or spring.

     Note: The pinion seal can be installed after seating the front bearing on the pinion shaft. If that seems easier, install the flange without sealant, pulling the front bearing onto the pinion shaft. Stop short of preloading the bearings at this point! Remove the flange and install the seal. Reinstall the flange as shown here.

Flange in place

Step 94: Flange can be pulled into place with the washer and modified (no locking edge) pinion nut used for your shim tests. Keep the shaft on center as you tighten the nut. Use the flange holding fixture and air impact gun. Draw up slowly and steadily. Do not crush the sleeve yet.

Pack washer with RTV

Step 95: Remove temporary nut after seating the flange against the crush sleeve. The bearing is in place, securing the shaft as the nut and washer come off. Coat the washer face with sealant, fill the cavity around the base of threads as needed.

Thread locker on pinion nut threads 

Step 96: Some use 271 Loctite high strength (red) on the new pinion nut threads. The nut is self-locking, and Loctite 242 (blue), applied generously, is a good safety margin and added sealer. Your choice.

Self-locking new pinion flange nut

Step 97: New pinion nut, provided in the Superior Axle & Gear install kit, now has coating of Loctite 242 on threads. If you use an air wrench at this point, be certain not to over-tighten the crush sleeve! Torque required to crush the sleeve is very high (300-plus ft. lbs.). Use any high torque air impact wrench with caution.

     Caution: You must not over-tighten the crush sleeve, or you will have to replace the sleeve with another new one. Overtightening cannot be followed by simply backing off the nut, although unaware installers have done this. The result is an unloaded front pinion bearing and risk of bearing damage...Worse yet, the pinion nut could loosen, and the shaft and gear set fail. The force of the crush sleeve is a key element for bearing preload, keeping the pinion nut secure and holding the front pinion bearing in position.

C-P 7288 Air Impact

Step 98: New acquisition for this project is the Chicago Pneumatic Model CP7748 composite air wrench, a great value in the $200 range. (We paid $199 plus tax through NAPA, including a nylon carrying case.) In real terms, this impact can controllably crush a new pinion sleeve.

  Note: See specs below. This 1/2-inch air wrench lives up to claims, delivering peak torque at a lower CFM than much more expensive products. Some manufacturers claim even higher torque output but require 29 CFM or an unrealistically high rpm to do so. Watch the rpm and air requirements on air tool ratings...

C-P 1/2-inch air wrench

   The CP7748 is an exceptional 1/2-inch air wrench for the price. Here are specs for the CP7748 air wrench:    

Working Torque Range (fwd) 75-580 ft. lbs.
Maximum Torque (reverse) 920 ft. lbs.
Free speed 8200 rpm
NetWeight 2 kg/4.4 lb.
Length 7.6"
Average air consumption 5.2 CFM
Actual air consumption 21 CFM
Air inlet thread size 1/4-inch pipe thread
Minimum hose size 3/8"
Noise level 93 db(A)
Sound Power 104 db(A)

Inch-pound torque wrench for pinion preload

Step 99: Actual specifications for a pinion bearing load are in inch-pounds. This flexbar Duro wrench has adjusted transmission bands and pinion bearing preloads for decades. Reliable and easy to read as the shaft rotates, a flexbar torque wrench works well for this kind of task.

Setting bearings

Step 100: Crush sleeve coaxed very slowly with the air wrench, the rotating torque was stopped at 22 inch-pounds for the new bearings. After stopping at 22 in-lbs, we lightly rap the shaft from both the front (shown) and gear head end with a sand head plastic hammer. This seats bearings. Re-check rotating torque.

Finished pinion installation

Step 101: Pinion flange is sealed and seated, with the crush sleeve compressed at 22 inch-pounds of rotating torque (different than start-up torque). 20-25 in-lbs is factory recommended for new pinion bearings in an AAM 11.5" axle.

Pinion depth now correct

Step 102: Based upon the shim and tooth contact tests, this should be the optimal height/depth for the pinion gear head. Marks on head of AAM gear are not pinion variance readings like Dana and other axle types. The best setting overall is a correct tooth contact pattern, correct backlash and 0.002" or less ring gear runout.

     Note: Runout is the waver of the gear, not to be confused with the required backlash between teeth. Ring gear runout is determined by either: 1) a magnetic stand and roller tip dial indicator check while rotating the ring gear's smooth edge or 2) by checking backlash at 90-degree increments of the ring gear and comparing results. The simple ring gear backlash test for runout works just as well. Compare the variations at the 90-degree points as you check the ring gear backlash!

Ring gear and carrier back in the axle

Step 103: Carrier and ring gear assembly rolled into the axle for what should be the last time! Adjusters backed off, make sure the bearing caps line up with the pin marks on the housing. Based on pre-tests and the right shim stack on the pinion, the gear set should only require backlash and bearing preload adjustments—followed by a loaded tooth contact pattern test.

Loctite 242 on bearing cap bolts 

Step 104:  All bolt threads have been cleaned and wire brushed as needed. Here, Permatex 242 blue thread locker provides insurance against bolt loosening. It also offsets natural loss of bolt torque over time.

Bearing caps in place  

Step 105:  Bearing adjuster rings can rotate if bearing cap bolts are slightly loose. Run bolts up hand tight then backed off 1/4 to 1/2 turn, leaving just enough clearance for carrier bearing cups to move laterally as the adjusters turn.

Adjusting for backlash

Step 106:  Rotate the left/crown side adjuster toward the carrier. Tighten just enough to remove gear backlash. Now you can tighten the right side adjuster. At zero backlash with the left adjustment, remove the play from the right side bearing.

Set up dial indicator

Step 107:  Before tightening the bearing preload at the right side adjuster, set up your dial indicator as shown. Angle should allow the dial indicator plunger to move freely while meeting the ring gear tooth close to its rotational centerline. Allow plenty of plunger range on the dial indicator. Finger snug the bearing cap bolts, allowing just enough slack for adjuster movement.

Setting carrier bearing preload

Step 108:  A quick setting for preload is 6 adjuster notches for new bearings. After carefully adjusting preload, check the gear backlash. Some like 0.008"-0.010" on an 11.5" axle. The Dodge Ram shop manual calls for optimal 0.005"-0.007" backlash with an acceptable range of 0.003"-0.010". 0.006" is our goal with a 6-notch preload on carrier bearings.

  Note: With backlash correct and preload at 6 adjuster notches, check the pinion rotational load as shown. 42 in-lbs works very nicely here, a combination of the 22 in-lbs with pinion bearings alone and the added carrier bearing preload (without axle shafts in place).

Adjuster notches within reach of spanner tool

Overall rotating torque

Step 109:  If backlash is off with the preload correct, you can move adjusters as needed and evenly—one notch loose at one side means one notch tighter at the other side. Work this until backlash is right, and verify overall preload (42 in-lbs in this case). Factory range with new bearings is 30-50 in-lbs for overall bearing load (pinion plus the carrier).

  Note: 22 in-lbs at the pinion plus 20 in-lbs additional from the carrier achieves the 42 in-lbs total. This is a good profile.

Final tooth contact patterns

Step 110:  Place some load on the pinion flange and get a tooth contact impression. If okay, as shown here on both the drive and coast sides of the teeth, install the axle shafts before the final, loaded test. Using Permatex 242 on threads, torque the bearing cap bolts and install spring locks. Tighten cap bolts in steps and cross pattern. Torque to 153 ft. lbs. Index springs at the adjuster notches; set lock spring bolts at 18 ft. lbs.

  Note: Bearing cap bolts should be final torqued to 153 ft. lbs. ("207 ft. lbs." is incorrectly stated in Dodge Ram manuals; that should read 207 N-m, which converts to 153 ft. lbs.) Once tooth pattern is right, torque these bolts in cross and steps. After reaching 153 ft. lbs., let bolts stand for a few minutes, then re-check. Verify pinion rotating torque, it should be correct at this stage—adjust if necessary.

Lock springs in place

Step 111: Run gear contact all the way around before installing axle shafts. Note the correct depth into the teeth and the length of the contact area. Backlash is now 0.0055", half way between 0.005" and 0.006", optimal for break-in to a final spec of 0.006". There is no ring gear runout issue, a tribute to the quality of the gear set.

Note: There are two types of gear cuts. Our 11.5" AAM axle pattern follows the two-cut style. For details on the modern ring-and-pinion tooth cutting styles, see the American Axle & Manufacturing explanation and diagrams.

Installing axle shafts

Step 112: Install the axle shafts before final tooth contact test. The best axle flange gaskets are Felpro's impregnated type that do not require RTV sealant. (This impregnated #55328 gasket for the Dodge Ram came from NAPA.)  Avoid using RTV sealant, which has created issues like breakdown of silicone and migration of RTV into bearings and gears. Use Permatex/Loctite 242 Blue on clean axle flange bolts. Make sure axle shafts are clean.

Slide axle shafts into place.

Step 113: When installing axle shafts, hold the flange in a way that keeps the axle shaft on center. This will prevent banging of parts and potential damage to the differential case, bearings or splines. Oil shaft inner splines and slide the shafts without force. Allow them to find their way into the side gear splines. Axle shaft bolt torque for the Dodge Ram is 95-100 ft. lbs. Bring torque up gradually and in cross (below) with parking brake set.

Torque axle flange bolts to 95-100 ft-lbs.

Test tooth pattern under load.

Step 114: For this final torque test, the adjuster locks are in place, torqued to 18 to 20 ft-lbs with Loctite 242 on the threads. Axle shaft flange bolts should be tight so that the parking brake can be set to drag lightly. Create around 10 ft. lbs. of pinion flange resistance for this tooth contact pattern test. Rotate pinion flange in both directions...This is the correct final tooth contact pattern.

Coast drive side tooth patterns 

Step 115: Under load of 10 ft. lbs. drag from the E-brake (no more), the tooth pattern looks good all the way around. Note the smoothing and clear impression created as the brake drag simulates load. Coast, drive, relationship of heel and toe, root and crown of teeth, this is a desirable result!

Close-up of tooth contact pattern

Step 116: Close-up of drive pattern shows ample tooth contact length, the right engagement depth of pinion, with correct margins above and below the contact areas. This is proof that 0.006" backlash will work well in this case.

Coast pattern correct

Step 117: Correct coast pattern will run quieter and provides long service life. On deceleration with a trailer in tow, down an 8% grade, it's reassuring to know that the ring-and-pinion teeth engage like this!

Clean off ring gear marking paste

Step 118: Wipe off the ring gear teeth; denatured alcohol works well if needed. Vacuum out the axle cavity and around the differential to remove any debris from the adjusters or marking compound residue.

Axle work completed and ready for cover

Step 119: All hardware is torqued to specification, tooth contact is right, and bearings have correct preload. This axle is ready for the cover and an oil fill!

Glass bead differential cover

Step 120: Differential cover removed, it's time for cleaning and paint. This OEM cover has minor rust formation, enough to require glass beading. Bolts can be wired brushed.

Rust on diff cover

Step 121: Rust beneath the OEM paint requires glass beading. This is strictly surface, as the Ram 3500 has resided in a high desert climate since new. Axles receive little paint in the manufacturing process. We'll fix this.

Diff cover like new

Step 122: Differential cover looks like new after glass beading, wash and dry. A coat of primer and a fresh coat of semi-gloss black paint will restore the cover. The inside will not be painted.

OEM style diff cover gasket

Step 123: Chrysler's differential cover gasket is exceptional. This part can be reused if in good, leakproof condition. Use Loctite/Permatex 242 blue on cover bolt threads. Install bolts using cross pattern.

Torque cover bolts

Step 124: Tighten differential cover bolts in steps to a torque setting of 30 ft. lbs. Do not over-torque, or you will distort the cover. Fill plug torque is 24 ft. lbs.

Attach driveshaft

Step 125: New OEM bolts at pinion flange are recommended in factory shop manual. Align your disassembly indexing marks. Tighten bolts in cross, on the Dodge Ram, the spec is 85 ft. lbs. Use Loctite 242 on clean bolt threads.

Pour synthetic oil into differential

Step 126: Oil type is a controversy. My choice here is Mopar Synthetic 75W-140 weight gear lube. Some believe break-in lube should be a 75W-90 or even a straight 90 wt. The main objective during break-in is to protect the axle from overheating.  75W-140 offers the widest range of temperature and load protection.

Run-in oil and break-in

Step 127: Four quarts of Mopar oil is 128 fluid ounces. Fill for the 11.5" Dodge Ram axle is 122 fl. oz. Four quarts is close enough on a complete axle drain with axle shaft removal and cleaned parts.

Dodge Ram 3500 after a road test

Step 128: After putting fluid into the axle, we idled the truck unloaded (in low gear) for ten minutes on jack stands to circulate oil and allow the bearings to fully saturate with oil. We then installed wheels and tires before taking a light test drive on the road. With proper break-in, this rugged axle will be trouble free for several hundred thousand miles.

Break-in Footnotes

  Axles require break-in after rebuilding, just like an engine! Axle concerns during break-in are heat and load, as gear teeth establish a lifetime contact pattern.

  Most builders recommend initial short trips under light load, allowing the axle to cool down completely between runs of 10-30 miles. This goes on for a couple hundred miles, without trailering or extreme acceleration loads. At 500 miles, towing can begin, with complete cool down periods and short runs during the first tows.

  Change the oil warm at 500 miles. This will remove any gear coating that could be floating around the axle. Use appropriate oil at the refill, consider your climate, driving conditions and axle temperature exposure.

     For coverage of the Dodge Ram 3500's 9.25" AAM front axle gear change, see the magazine's HD video rebuild of the AAM 9.25" beam front axle! Click here for access to the 4WD Mechanix HD Video Network how-to video. Basic axle work is similar for G.M. truck applications that use the 9.25" center section.

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