How-to: Dodge Ram AAM 11.5" Axle
Rebuild with New Ring & 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
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
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
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.
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
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
Skill level required: Familiarity with gear mechanisms and ability to follow technical
Needed tooling: Specialty tools required—review the steps before taking on this kind of
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.
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.
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
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.
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
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.
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
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
not damage the metal! You are merely spreading these parts at the
gasket, not chiseling or nicking metal.
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
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.
Step 11: Spring locks keep
the differential bearing preload nuts from rotating. Remove these bolts and springs to make adjustments or
remove the differential...
Step 12: Loosen opposite
retainer bolt and spring lock. Note the relationship of these parts for
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.
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.
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!
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
Warning: The 11.5" differential carrier and
ring gear are heavy and can cause severe physical injury if not supported during
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.
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.)
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
#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
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
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
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
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
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.
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.
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
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.
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
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
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
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
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.
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
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
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
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.
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.
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
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.
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).
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
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.
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
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.
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.
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.
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.
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
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!
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).
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.
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.
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
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
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
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 &
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
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!
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
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!
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
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...
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...
Step 58: This tool also
clears the differential carrier flange at the inside diameter of the
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
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!
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
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
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
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
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
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
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.
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
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.
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
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.
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
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.
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.
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
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.
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.
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
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
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.
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
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
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
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.
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.
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
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.
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.
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
Note: The Miller-SPX 8883A spanner will only loosen these adjusters so far.
Adjuster holes "disappear" into the housing, becoming narrow
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.
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.
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.
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.
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!
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
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
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
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.
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.
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
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
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: 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
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
The CP7748 is an
exceptional 1/2-inch air wrench for the price. Here are specs for the CP7748 air
Working Torque Range (fwd) 75-580 ft. lbs.
Maximum Torque (reverse) 920 ft. lbs.
Free speed 8200 rpm
NetWeight 2 kg/4.4 lb.
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)
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.
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.
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"
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
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
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.
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
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.
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.
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.
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
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.
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.
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
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.
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.
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
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!
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
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
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.
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!
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.
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
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.
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
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.
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
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
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.
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.
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
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.