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Q&A: Willys, Jeep CJ, Jeepster Axle, Transmission and Transfer Case 

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Jeep front axle under construction with Air Locker

Front Axle Parts for a Spicer 27 Axle

From: 1968 CJ-5 Owner
Sent: Wednesday, September 26, 2012 8:56 AM
Subject: Dana 27 Front Axle Confusion

I'm in the process of reworking my 1968 CJ5 front axle. Could you tell me the difference in a Dana 27, 27A, and 27AF. 27A is stamped on my front axle hsg. My 1966-1971 Jeep Service Manual SM-1046 Section M refers to service procedures for the 27AF only. Also my Jeep Universal Parts Catalog W-1195 R2 Group Number 20 refers to 27AF. Are parts for the Differential inter-changeable within these three Dana's I have mentioned?

The 27s should each be the same for parts. They were officially Spicer axles, though Dana has been a parts source in the aftermarket. Compare parts to be certain of fit…The difference in the use of the 27 versus the 25 was the gear ratio and housing clearance for the ring gear and carrier. For differential parts sourcing, I have always relied on the “27” or “25” designations, not the housing suffix letters.

Let me know if this helps. I have plenty of information if you need more details...

Regards,

Moses

 

Owner Picks an Axle Ratio for AMC Era CJ

-----Original Message-----

From: Chad A.

Sent: Tuesday, April 19, 2011 7:54 AM

To:  4WD Mechanix Magazine

Subject: Differentials 

 

Moses, 

 

A new dilemma. My front differential is a mess. It was 3/4 full of dirt, gears are unusable, carrier gears are questionable, and the shims are so rusted and chewed up, I can't get a good indication from them. Hopefully, the housing is in good shape. I will find out when it get it cleaned up. 

 

The worst part is, the gears are 2.72s. Trying to keep my budget in check, I located a good used set of gears and open carrier. Before I purchased the gears and carrier, I thought I should pull the rear diff cover off just to ensure the gear ratios were the same. When I broke the cover loose, a quart of water came out before the oil. Upon further inspection, I found the pinion wobbling. Looks like I will be rebuilding both differentials. Luckily the rear diff looks like it will only need an overhaul kit. 

 

So, here is my dilemma. If I have to rebuild both differentials, now is a good time to change out my gear sets to something taller. A limited slip or air locker in the rear would be a great upgrade also. Unfortunately, rebuilding both diffs, swapping gears, and replacing the carriers with a locker/limited slip or keeping it open will be more than my budget can afford. I am trying to weigh out if I should rebuild the differentials with the stock gears or wait and upgrade. If I stay with the 2.72s, I will go down to the 31" tires as planned but, I am concerned that even 31s are going to be too much for the 2.72s to handle. I am surprised the 33s didn't totally skyrocket both diffs. That is a lot of torque against a high gear. 

 

If I wait, it may be a long wait. I don’t mind rebuilding now and upgrading later. Do you think I should be concerned with the 2.72s? I know my driving is going to be mostly on-highway with the occasional trail or shallow mud pit. I don't have the 4wd background to make a logical decission. I could use your advice again. 

 

Thank you,

 

Chad

 

Hi, Chad...Even with 31" tires, I would want 3.73 or lower (numerically higher) gear sets. Even without overdrive, a 3.31:1 or 3.73:1 ratio would be advisable for 31" diameter tires.

 

At 33" tires, I prefer 4.10 gears or even 4.56:1 (primarily trail use).  (If gas mileage is a concern, the 4.10s would be better.)  Given the labor involved, I would not rebuild two axles without installing the correct ring-and-pinion gear sets.  2.73:1 would be ridiculously tall (numerically low) gearing for a Jeep CJ, and you will be very unhappy with that ratio and 31" to 33" tires.

 

My Jeep CJ Rebuilder's Manual will prove very helpful for the rebuild process.  Ring and pinion gears are available from a variety of sources.  Prices, including the overhaul kits, are not that expensive. Let me know your choices...

 

Moses 

Wagoneer Front Axle Install on an '85 CJ-7

From: Ben S.
Sent: Monday, January 10, 2011 6:26 PM
To:
  4WD Mechanix Magazine
Subject: Dana 44 front end SWAP (Jeep Wagoneer FRONT DANA 44 retrofit into a 1985 CJ-7)

Hi Moses , I have been a Jeep member with Patriot Jeepers, driving my CJ-7, adding and updating (good friends with Rich B.). I just started a front dana 44 swap from a jeep wagoneer (passenger side pumkin drop like a cj.) I am just shortening one side like you recommended in the CJ manual on a cj5).

I use and love all of your Jeep technical books and like doing most of my own work…I remember meeting you at the tech session at Bentley Publishing. Looking to swap Dana 44 gears myself…Can you recommend any simple reference books. I may need to buy a few tools . Thanks for any info...Ben S.

Reply from Moses Ludel:

Hi, Ben…I surely remember our gathering with the Patriot Jeepers at Bentley’s shop…We had a good time! Thanks for your continued support for my books. The 4WD Mechanix Magazine website is a growing resource that you will enjoy.

If you have the 1972-86 Jeep CJ Rebuilder’s Manual, I do cover the Dana 30 low-pinion axle build there. In the earlier 1946-71 book, I cover a Spicer 44 axle built. For procedures and layout, the Dana 30 low-pinion is similar to the low-pinion 44 that you have from the Wagoneer. (Torque specs for hardware will differ slightly.) Also, at the website magazine, you will find my build of a Dana 30 high pinion with an ARB Air Locker. If you need info beyond that, you want the factory axle data for the Wagoneers and Grand Wagoneer, found is a Jeep factory workshop manual for that period.

As for tools, my CJ manuals talk about creative ways to mimic the factory-recommended (i.e., sometimes expensive!) tools. Review the chapter on axle builds, you’ll get the idea. As for narrowing the axle housing, Rich has recently done the same with a Scout axle. He chose your local shop, Mitchell Machine, to narrow the housing and axle shaft. We discussed axle shaft modifications, and Rich can provide details.

My Jeep CJ Rebuilder's Manual should provide the framework and moral support you need for tackling an axle build!

Fitting a Scout II Front Axle to a 1986 CJ-7

From: Rich B.

Sent: Sunday, November 07, 2010 9:51 AM
To:
4WD Mechanix Magazine

Hi Moses...I'm working on putting a 1980 Scout Dana 44 front end with stock 3:73 gears under my '86 CJ7. I cut off the ears and spring pads and have to cut the long side. What do you think is better for the front end as far as lunch box lockers go? I just ordered a Spartan lunch box locker. I know what I'm getting is "only pieces in a box", but I'm on a budget. This is why I picked up a 1980 Scout Dana 44 front end with the same gear ratio as my rear Dana 44 3:73's. I have 6 bolt Warn lock out hubs on my 86 CJ7.

I ground the spring pad on the short side for better pinion angle. I already pulled the chuck out and have to set the caster angle 6-7 degrees. I found out IH in 1980 (the last year) set the camber at 0.5 degrees. How did they do this? Was it built into the knuckles or the ears?

I plan to heat the knuckles up on the grill and cool down the axle, then slide them on and into place, measure and set the degrees and weld. Did I miss anything? Oh, yeah, I have to weld the long spring pad back on. I have a AC-DC stick welder, and I'm a welder. Got a 110 MIG for those small jobs.
 
Thanks,

Rich B.

Reply from Moses Ludel:

Rich, there is very little difference between the “lunchbox lockers”, whether the LockRight, Detroit EZ Locker or Aussie Locker. Actually, I recommend an ARB or similar manual locker for the front axle. Automatic lockers, including the lunchbox types or a Trac-Lok OEM design, have been useful in some applications—but not, in my view, for a 94-inch wheelbase vehicle like yours.

Any automatic locker at the front can be a hazard on an off-camber road or trail consisting of ice, snow or mud. I want the front axle “open” when desired and locked when necessary. Though the manual lockers cost more, they provide far more flexibility and permit precise, 50/50 torque distribution to each front wheel when needed.

I use the ARB Air Locker personally. On most trails, I run the front axle open to protect axle shaft U-joints and permit a tighter turning radius…Since you have onboard air already, you could use regulated, stored air from that system to run the ARB Air Locker…This would save buying an ARB compressor for the locker. Eventually, if you rebuild your Dana 44 rear axle, you might add an ARB unit there as well.

Since you currently have a Dana 30 limited slip up front, there’s the possibility that you could live with the driving quirks of a limited slip at the front axle. If so, you might consider a Trac-Lok differential for the new Scout 44 front axle; this does require changing to a limited-slip type differential carrier, which bumps up the cost. Compare overall cost to an ARB.

Are you curious whether camber setting is made with the knuckle support (ears)? I have always understood that the tubes are true, on center, no “degrees” of bend. SAI, caster or camber measurements are created by the location and design of the knuckle support on the tube ends.

I have details on each of the I-H axle settings from the era you describe. Do you know the I-H axle designation for your 1980 Scout front axle? It should be “FA-….” If you can furnish the I-H identification, I'd be happy to share the axle and front end alignment figures for this Scout/Dana 44 axle.

5-7 degrees of positive caster is normal for a later beam axle 4x4. I like 6-7 degrees, as I-H notes. 0.5 degrees of positive camber angle is acceptable for a Dana 44 axle, although Jeep beam axles typically start at zero degrees, plus-or-minus a slight amount, with the wheels pointed straight ahead.

There is also steering axis inclination, which can be 8-13 degrees on an open knuckle beam axle. Steering axis inclination, or ‘SAI’, is determined by the position of the “ears” (as you refer to them) and the pivot angle of the spindle/knuckle. If caster and camber readings are correct, the SAI should be within specification. If not, the steering knuckle is damaged. On a beam axle, the housing ear alignment would affect all three of these readings.

When you weld the knuckle support (ear pieces) back onto the beam tube, imagine a bar running through the centerline of the ball joints. The tilt of the bar, inward or outward, would affect steering axis inclination (camber, too!). If you match this angle with a known knuckle support, like the untouched opposite side of the axle, and if the knuckle/spindle support lines up identically, SAI should be correct. With straight ahead wheels, the camber should be close to zero or only the minor degree of tilt required. (See my article on wheel alignment, Rich. To access the article, click here.)

If the opposite side has not been removed or tampered with, you can use it as a template for caster angle and knuckle support alignment. Fit a bar through the two ball joint seats to create a measuring point for matching caster and SAI angles. If you removed both knuckle supports without marking their positions, install the steering knuckles and spindles onto the knuckle supports (ears). Mount the knuckle/spindles and the knuckle supports onto the axle tubes. Measure the camber and caster angles with the spindles in a position equivalent to the straight ahead wheel position. For a correct reference point, this is the place to start. See my article for details on alignment positions…

I trust this helps. I’m available if you need further clarification.

Response from Rich B.:

Hi, Moses, I talked to Mitchell's drivetrain right down the street from me. They cut down axles, and I had them weld up the axle so it will track right down the road. They set up a jig and have done may axles for people. If I was just going to run it in the woods, I would weld it myself. Mitchell's cut the housing on the long side 3-5/8", set caster and camber, and rewelded the ears back on. They reset the pinion angle, added a drain plug, new bearings, seals, breather, and cut and re-splined the axle shaft with new U-joints.

I gained axle stamina, a Spartan front locker, a larger ring and pinion, larger axle shafts, bigger U-joints. I'm not sure when I'll get it in the CJ7—maybe spring.
 
Rich B.

Moses writes back:

Hi, Rich! Sounds good…Unless the axle shafts were originally through-hardened, I’m assuming that Mitchell re-heat treated the newly cut axle shaft splines. (If they cold cut and cold splined the shaft, there is still a need to either know or check hardness depth.) For some axle shafts, cutting new splines will machine below the axle shaft case hardening or heat treatment. Soft splines will not hold up for any length of time. If there is a need for heat treating, do so to OEM depth and at least factory Rockwell C hardness…A heat treating shop should know the hardness and required depth of heat treatment. They can Rc test the other (unmodified) axle shaft’s splines as a place to start.

Rich, I would take the two front axle shafts to a shop with a Rockwell hardness tester. (Mitchell may have a tester. A heat treating shop surely would have one.) Have the shop Rockwell test the hardness of the splines on the unmodified factory axle shaft. Have them test the splines that were just cut. If the splines are the same hardness at the full base/root of the cut, that would be okay. If the new splines are not the same hardness at the root/base of the cut, then the shaft had originally been case heat treated, and the newly cut area, cut below the case hardening, is softer. If the axle shafts are case hardened, that hardening is only so many thousandths of an inch deep. If the original shafts were through-hardened, then cold cutting (not allowing material to heat enough to normalize or anneal the metal) the new shaft splines should not affect hardness. The quickest answer is a Rockwell C hardness test at the base/root of the splines. 

 

Mitchell may have a Rockwell hardness tester, many machine shops do.  If not, all heat treating shops have a hardness tester. Splines need hardness testing to the base of the cut. Make sure the spline hardness is tested to the root of the spline cuts and not just at the shaft surface.  If the shafts were originally case or surface hardened, the top of the new splines could be hard while the root or base of the spline cut is soft.  (Machining splines would cut through the case hardening depth.)  Mitchell did the right thing by cold cutting. This is not about Mitchell’s cutting method. It’s about whether the original axle shafts were case hardened or through hardened.

 

Let me know the outcome here…I am curious what the new splines read compared to the old ones when measuring spline hardness at the base/root depth of the splines.

 

Moses

Rich B. comments: 

Thanks for the information, Moses, I will discuss this with Mitchell's shop. On another note, I'm only running 3:73 gears with a T18 and Dana 300, 33" tires and the 258 with a Weber carb. Do you think I could go with a 34" or 35" tire? 34" is an odd size. Is 35" too big? I've got a 4" suspension lift and 1" body lift.

Moses Ludel replies:

Hi, Rich…With the 3.73 gearsets, I would not run tires any larger than 33” diameter. Your T18 (if Ford truck origins) should have a 6.32:1 compound first gear, which works well with 33” tires and 3.73 gears.  I’d stick with the 4-inch lift and be happy with 33” tires. Otherwise, you’ll be changing the axle gearing to compensate for the overdriving effect of larger tires. My thoughts…

Dana 300 Speedometer Tooth Count

Hello, Moses, we met years ago here in Massachusetts…I have an ’86 CJ-7 with a 258 six, T-18 transmission upgrade, Scout TC146/Dana 300 transfer case with twin-stick, Dana 30 with 3.73 gears in the front and Dana 44 rear axle with locker. Tires are 33” mud type, and I use an 8274 Warn winch, York on-board air system and other accessories for off-road use. I've had my ‘86 CJ7 for 20 years now. The Jeep T-18 mates nicely to the Scout/Dana 300 transfer case, and I need a speedometer gear for the unit. Do you have any ideas where I might find a gear? The Scout gear teeth are the opposite cut to Jeep.—Rich B.

Hi, Rich, I do recall meeting! For readers who do not understand why your 1986 CJ has a Scout transfer case, here’s a quick recap. In 1980, both Jeep and I-H Scout changed over to the Dana 300 transfer case, a wise choice and a good unit. Jeep adapted a modern, circular bolt pattern on the input end of the case, a pattern now familiar to many 4x4 applications. Scout, having parts like the T-18 transmission in inventory, had Dana build a 300 unit with a unique flange pattern. This pattern is the same as the earlier Spicer 20 applications and fits the pre-1980 Jeep and Scout transmissions. Since 1980 Jeep models with the Dana 300 and a T-18 are virtually impossible to locate, the Scout units became a nice conversion tool for mating a stock Jeep (pre-’80) or Scout T-18 four-speed transmission (heavy-duty, truck type with compound low gear) to a Dana 300 transfer case.

That said, I recall Jon Compton at Border Parts, Spring Valley, California, phone (619) 461-0075, having pallets of new Dana 300 Scout transfer cases stacked up at his store during the 1980s. Jon bought out these units when Scout went out of production and Dana had an overload of quality units. Rich has one of these unique units. Border Parts might be a supplier of speedometer pinions for the I-H Scout transfer case and other Scout/Dana 300 pieces.

When these Scout transfer cases sold out, Advance Adapters kits mated the more common Ford truck (2WD) T-18 type transmission to a Jeep/Dana 300 transfer case. This has become the swap routine for installing a T-18 truck transmission with compound low gear into a 1980-up Jeep CJ.

For Jeep owners of 1980-86 models that have the original Dana 300 transfer case (stock), here are the factory, driven gear tooth counts and OEM Mopar part numbers for ’81-’86 CJ speedometer pinions:

GEAR, Speedometer Driven: 

J3212724 24 Teeth - White

J3212725 25 Teeth - Blue

J3212726 26 Teeth - Red

J3212727 27 Teeth - White

J3212728 28 Teeth - Blue

J3212729 29 Teeth - Black

J3212730 30 Teeth - Yellow

J3212731 31 Teeth – Green

J3212732 32 Teeth - Black

J3212733 33 Teeth - Yellow

J3212734 34 Teeth - Green

J3212735 35 Teeth - Orange

J3212736 36 Teeth - Red

J3212738 38 Teeth - Blue

J3230221 39 Teeth - Green

J3230222 40 Teeth - Orange

53001488 41 Teeth - Red

53001489 42 Teeth - White

J3238143 43 Teeth - Blue

J3238144 44 Teeth - Black

92000065 45 Teeth – Yellow

These numbers are good for OEM or NOS parts sources and can be crossed to others. 4WD Hardware sells speedo gears (pinions), too.

Determine the tooth count you need for your tire size and axle gearing. I suggest doing the math, which involves counting the output shaft drive gear’s metal teeth. (Look inside the speedo cable/housing opening at the transfer case and count the spiral teeth.) Determine the ratio between the metal gear’s teeth and the tooth count of the plastic driven/pinion gear. Change the tooth ratio to accommodate the percentage of speedometer error.

Another approach if all of this is futile: Stewart Warner makes a speedo drive gear box that fits in line between the speedo cable and the existing drive mechanism. The device is a small gearbox with interchangeable gearsets to factor for tire and gearing changes. Though sometimes costly, this does provide options if you plan to change the tire size or gear ratios on a regular basis. These speedo gearboxes were common on older, medium duty and larger trucks. You may find such a device through a recycling source. Be sure that S-W has the gear sets needed to correct your speedo error before trying this alternative. 

1945 Jeep CJ-2A carries over many of the WWII MB's features. Shown is a stellar restoration at the Jeep/Mopar Pavillion, Moab, Utah.

Is the 1947 CJ-2A a Candidate for Overdrive?

From: Lex L.
Sent: Monday, December 06, 2010 10:40 AM
To: 
4WD Mechanix Magazine
Subject: jeep question

bought a 1947 jeep all original in fair condition going to try to restore it from the ground up, bought your rebuilders manual to help me through. my question is with that over drive installed will you be able to get 55mph out of that engine. Not interested in alot speed just dont want to be a road nusance.

Lex L.

From:  Moses Ludel
Sent: Monday, December 06, 2010 8:42 PM
To: 'Lex L.'
Subject: RE: jeep question

Hi, Lex…Happy to answer your question…The Warn/Saturn overdrive is, from most calculations, a 25% reduction in engine speed and usable in any transmission gear. The overdrive is designed to work in 2WD (high range), 4WD low range and 4WD high range.  It attaches through the auxiliary PTO port and works with each transmission gear. With its synchronizers and use of the engine/transmission’s clutch, the overdrive can be effectively shifted at any time, allowing for split shifts of all transmission gears. Of course, the transfer case gears must be virtually stationary before shifting into and out of low range. Your axle ratios are likely 5.38:1, which is the same as the CJ-5 in my book, the Jeep CJ Rebuilder's Manual: 1946-71 (Bentley Publishers, Cambridge, MA).  3rd gear in the original T-90 3-speed transmission is 1:1.  If the Jeep is stock and has tires of no more than 31” diameter, you can use this overdrive somewhat effectively with 5.38:1 axles.  With 4.88:1 used on earlier models, you would be pressing it.  My advice would be to keep with 30” (no more than 31”!) tires if you plan to use this type of overdrive.

Will the unit help with speed on the highway?  That’s debatable.  The engine only produces 60 horsepower (at nearly 4,000 rpm), and peak torque is around 2,000 rpm.  If you can keep the engine above 2,000 rpm and below 2,500 rpm at 60 mph, the overdrive would be effective.  I ran some numbers.  With 30” and 31” diameter tires:

1)  30” diameter tires: Engine rpm at 60 mph with 5.38:1 axle ratio and use of the 25% overdrive in 3rd gear (1:1) would be approximately 2,700 rpm.

2) 30” diameter tires: Engine rpm at 60 mph with 5.38:1 axle ratio and no overdrive in 3rd gear (1:1) would be approximately 3,600 rpm.

3) 31” diameter tires would knock the engine rpm down to 3,500 without overdrive at 60 mph in 3rd gear (1:1).

4) 31” diameter tires would knock the engine rpm down to just over 2,600 rpm in 3rd gear (1:1) at 60 mph using overdrive.

While this makes the overdrive sound practical, in real world terms, this is a very light output engine.  Peak torque is barely over 100 (105 @ 2000 rpm).  Horsepower peak at 4,000 rpm is where this engine would need to be in order to sustain speed under any kind of grade or load.  That kind of rpm is quite scary with a 3-main bearing crankshaft and early alloy pistons that are susceptible to burning holes in their crowns when stressed—even with the ridiculously low 6.48:1 compression ratio.  One thinks of the long, spindly 1930s-style connecting rods quite often when spinning this engine beyond 3,500 rpm!…The overdrive might be effective on a flat cruise, taking the speed down some when the engine has a light load.  Again, the staggeringly sluggish acceleration rate in overdrive would hardly meet the demands of a modern highway. Take my word here, as I did drive the CJ-5 with my blueprint F-head rebuild and overdrive. On the highway, it was clearly no world beater.  The F-head produces 15 more horsepower and 15 ft-lbs more torque than the L-head you have in your CJ-2A.  For 1953 CJ-3B models, this was an accomplishment. By today’s high-tech standards—well, that’s enough said about this old 134 workhorse!

The earliest serial number CJ-2A models came with column shift transmissions. This quickly gave way to the distinctive cane shifter. 

Most consider the vintage 4-cylinder L-head models a 50-55 mph peak.  Realistically, 55 mph is not easy to hold with stock gearing and even more difficult with overdrive.  I would pretty well dismiss the overdrive idea for the highway as a way to keep up with traffic.  However, it does have one asset: synchronized split shifting capability.  This would make it possible to use 2nd gear overdrive on a light grade as needed or, effectively, have 12 speeds forward and four reverse speeds when used in high and low ranges of the transfer case.  If you can think of enough reasons to justify the variety of gear ratios available, the overdrive might be advantageous.

That’s my take.  Incidentally, the ’55 CJ-5 will be using its overdrive with a very nice 3.8L Buick V-6 powering the operation.  You will find details in the book.  The NV3550 transmission has a 5th gear overdrive, so effectively the CJ-5 will have 20 speeds forward and four in reverse—counting use in high and low range.  The nice thing about the Warn overdrive design is the synchronizers and ability to shift it on the fly—with use of the clutch.  I heartily recommend light lever action on the Warn overdrive shifts to preserve the synchro unit and the planetary gearsets!

I trust this information helps, Lex…

Regards,

Moses Ludel

Dick Stowers' Classic '67 225 Buick V-6 CJ-5 Jeep T-98/T-18 Truck 4-speed has been a popular choice for CJs

CJ-7's T-176 Transmission: Planning Some Gearing Gains

I have a 1985 CJ-7 with a 258 6 cylinder engine, T-176 transmission, Dana 300 transfer case, 3.73 gears and 31" tires. The Jeep is too high geared in low range. I hear there is a kit for the Dana 300 to lower the low range gearing. What are my options?—George L.

George, your CJ-7 sounds virtually “stock” with the exception of 31” tires. The T-176 has a 1:1 ratio in top gear and a 1st gear ratio of 3.82:1. Your transfer case has a fairly low 2.61:1 ratio. While installing lower gearing for low range has gains (check with Advance Adapters for a gear kit), I prefer a T-18 or NP435 transmission conversion—for several reasons. A common approach is the Warner T-18, a relatively compact truck four-speed with a compound low gear and high gear of 1:1 like your current T-176. A popular conversion approach is the Ford 2WD version of the T-18, which has a 6.32:1 1st gear and a 2nd gear of approximately the same ratio as your current transmission. The non-synchromesh compound low gear is usable in both high and low range while 2nd, 3rd and 4th gears are each of synchromesh design. The T-18 offers more stamina by far than the T-176. If you opt for the NP435 transmission, this is even more rugged than a T-18 and has a compound low ratio of 6.69:1! If you do the math on either of these transmissions, you find that their gains in compound low gearing are equal to or better than a lower ratio gearset installed in the Dana 300.

For AMC-era CJ’s like yours, I have outlined this conversion in both my Jeep Owner’s Bible and the Jeep CJ Rebuilder’s Bible, 1972-86. Having rebuilt the Dana 300 (steps also covered in my rebuilder’s manual), I would note that the T-18 conversion is not difficult and provides a cost-effective solution for making your Jeep more versatile. There is also the NV4500 transmission conversion that I cover in the Jeep Rebuilder’s Manual: 1972-86. This is the ultimate transmission for strength and flexibility, likely overkill for most applications! The NV4500 has versions with as low as 6.34:1 first gear plus a 5th gear overdrive on top. All forward speeds have synchromesh, and an overdrive can improve fuel efficiency. More costly than a T-18 conversion, the NV4500 is for those who need—or want—a 1-ton capacity transmission with an ultra-low 1st gear plus 5th overdrive. 

Mating a 42LE Automatic to the Dana 300

My son has acquired a 42LE (A500) automatic transmission from a ‘94 ZJ Grand Cherokee. Can we bolt it up to a Dana 300 transfer case? Both have the 6-bolt mounting pattern. The engine is a 5.2L V-8, the transmission works fine, and we want to install the package in his late ‘60s Jeepster. I preached your idea of a V-6 for fit, but he wants to make power with a V-8.—Tom H.

Advance Adapters offers spacer plate adapters for the Dana 300 to New Process units and a variety of input gears. This is a special 32-spline variation. (Photo courtesy of Advance Adapters.)

This topic bears discussion! ZJ powertrains are abundantly available through recycling sources, both inline sixes and V-8s. Jeep builders should take the 5.2L Mopar V-8 seriously. A proven pushrod design with roots to 1957 (1967 in more modern form), the 5.2L and bigger 5.9L “small-blocks” deliver gobs of torque, horsepower and reliability. MPI/EFI adds to the ante.

The 42LE and Dana 300 mate-up requires 1) a common spline count on the transmission output and transfer case input and 2) the stick-out length of the 42LE output shaft needs to match up with the Dana 300.

A 1994 New Process transfer case should have a 23-spline input like the Dana 300. The transmission output shaft should be flush with the end of the OEM adapter. (Confirm spline count and stick-out length of the transmission output shaft.)

The six-bolt circular pattern is correct, although here you run into an issue. The Dana 300 and New Process transfer cases “clock” differently. The bolt pattern is the same spacing and circle, but the position of the bolts on the circular face differs between a Dana 300 and the New Process transfer case. The result is a transfer case that sets in a different rotation or clock indexing position than the stock application.

Note: Advance Adapters “clocks” the Dana 300 when replacing an NP231 or other NP transfer cases.

Advance Adapters remedies this with a spacer-adapter plate that accommodates each of these clock positions. However, unless your transmission has a stick-out of the output shaft beyond the factory adapter plate (not likely), the spacer will require changing to a longer input on the Dana 300.

Note: Advance Adapters’ P/N 50-8604 includes the adapter plate and a longer, 23-spline input for the Dana 300.

So, you need to verify output shaft length and spline count on the 42LE transmission. If you decide to continue with the mate-up of the 42LE to the Dana 300, you will need to index/clock the transfer case, which requires the adapter plate and, likely, the longer input for the Dana 300.

Interestingly, Advance Adapters does not do Mopar V-8 engine or transmission adapters. You can adapt a variety of Ford, G.M. and Aisin Warner transmissions, but there are no adapters to Chrysler transmissions, not even the OEM 904/999 Jeep applications.

Worth noting, however, is that your 5.2L V-8 is a candidate for a 727 Torqueflite transmission. This unit can mate to a Dana 300 or NP transfer case using an OEM adapter plate from a Dodge truck application with a 23-spline output. If output shaft stick-out length or clock position of the Dana 300 is an issue, you would need the spacer plate and long input kit for the Dana 300.

The transmission application would be a Dodge truck’s A727 fitted originally to a 318 or 360 V-8 in an ‘80s model pickup. Verify the 23-splines, or you can change the input on the Dana 300. Advance Adapters offers a variety of spline count inputs for the Dana 300.

Here, you would have a non-electronic, rugged 3-speed automatic that fits your ’94 Grand Cherokee 5.2L V-8 engine without the need for electronic controls or wiring. You would have a simpler and highly rugged automatic as well. The A727 was the transmission of choice behind muscle car era 426 hemi V-8s, used in Class A motorhomes and backed up the Cummins diesel in the original Dodge light truck applications to one-ton capacity!

Although there would not be an overdrive gear with this approach, the A727 Torqueflite would be my first choice in Chrysler automatic transmissions.

Another approach would be the 42LE as a package with its transfer case. This is a left-drop New Process transfer case. You would need to retrofit a Grand Cherokee or similar left-drop front axle to provide a left-drop front differential location.

There are a variety of newer beam type Dana front axles with left side offset differentials. You likely want to get away from the original Jeepster closed-knuckle, drum brake axle, so consider this option.

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