Did some more work on the gear swap in my brother's Duster today.

To recap:

Original axle: unknown year A body 8.25 axle with 2.2:1 gears. Everything fit together and it worked

Parts attemping to install: unknown year 3.5:1 ring, pinion, and carrier out of a early 70s Dodge van axle.

Attempt #1 (failed): remove 2.2 pinion, carrier, and ring gear. Install 3.5 pinion, carrier and ring gear. With this combination of parts the ring gear barely engaged the pinion gear. Adjusters were adjusted so the carrier was all the way over to the right.

Information learned: Measured carefully and determined that the ring gear needed to be .25 inches closer to the pinion. Compared the 2.2 carrier and the 3.5 carrier and determined that the 2.2 carrier puts the ring gear roughly .25 inches closer to the pinion.

Attempt #2 (failed): remove 3.5 carrier and ring gear. Installed 3.5 ring gear on 2.2 carrier. Installed 2.2 carrier with 3.5 ring gear into 2.2 axle housing. With adusters all the way to the driver's side of the car, the ring and pinion teeth mesh, but if the carrier bearing caps are tightened down the ring and pinion will not turn. With the pinion bearing caps slightly loose the gears will turn but make a loud grind and clunk when engaging. If the caps are loosened a little bit more the carrier will wobble up and down as the gears mesh.

Information learned: The 2.2 pinion has a much larger diameter than the 3.5 pinion (didn't measure). The 3.5 gears on the 2.2 carrier in the 2.2 housing will not mesh properly with the 3.5 pinion. This last part is key: The 2.2 gears are thiner in cross section than are the 3.5 gears. The 2.2 gears are 1.3 inches thick and the 3.5 gears are roughly 1.4 inches thick. Also, the 2.2 ring gear has a large flat spot on the pinion side of the teeth, towards the center of the ring gear (I believe this is the heel of the teeth). The 3.5 gears have a uch much smaller flat spot on the pinion side of the teeth.

Hypothesis#1: There is a physical difference between the 2.2 and 2.4 8 .25 axle housing and the 2.7 and up axle housing. I have read many sources that say that there is a break in the carrier housings between 2.4 and higher and 2.7 and lower gear ratios. I have confirmed that this is true. However, I believe that there is also a difference in the axle housing because the 3.5 gears would not mesh properly on either the 2.2 or 3.5 carrier.

Hypothesis #2: Hypothesesis #1, and/or the fact the 3.5 gears came out of a van means that they are 8 3/8 gears, NOT 8 1/4 gears, and there is some kind of dimensional difference between 8 3/8 gears and 8 1/4 gears that makes them incompatible with a housing of a different diameter.

Conclusion drawn from either hypothesis: I am screwed by using this axle. I have already spent near $1000 to purchase the axle, buy a rebuild kit, buy the gears, plus the hours of time spent rebuilding the axle and swapping all the gears around. Yet nothing is fitting together.

I have come across several threads on various Mopar boards from the last decade where someone ran into this same problem. The solution have been to abandon the 2.2 axle and get a different 8 1/4, order a locking differential and carrier from Randy's Ring and Pinion, or abandon the Mopar axle altogether and install a Ford rear axle.

Cheapest possible solution: get a grinder and grind the 3.5 gears down to 1.3 inches thick with a larger flat towards the pinion

Next cheapest solution: order a new set of gears from Randy's ring and pinion.

Third cheapest solution: order a locker and carrier from Randy's ring and pinion

Fourth cheapest option: install a different axle, Mopar or otherwise.

I'm pretty bummed, but at least I learned some good information. I was never able to find anyone who successfully install 2.7 or lower gears into a 2.2/2.4 8 1/4 axle housing without at least getting the locker and carrier from Randy's.

So, unless I am missing something, it looks like I am out the money and time I spent on this axle and I am back on the hunt for either a way to install 3.5 gears into this axle or a completely different axle. If I missed something or have made a mistake, I would be thrilled if someone woudl point out my error to me.

What happened to the ring gear spacer idea?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Nobody sells them and nobody sell the special left hand thread ring gear bolts in a length .25 inches longer than stock. The spacer just isn't an option.

For the bolts are you just looking at rear axle suppliers? If so, why not look elsewhere?

I haven't hit the specialty hardware suppliers yet, but if I can't find a spacer the bolts aren't worth looking into.

I can't see why a well equipped machine shop can't make one for you.

Greg

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http://www.youtube.com/hyperpack

Mcmaster-Carr (www.mcmaster.com) has grade 8 left handed bolts......


Can you machine down the 2.2 ring into a spacer?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

At this point I am leaning to just getting a completely different axle. Even if I fabricated a sparce and brought the ring gear closer to the pinion, the pinion is still not meshing properly with the ring gear.

When I installed the 3.5 gears on the 2.2 carrier, the gears were meshing but were not lining up properly. The gears locked up when the main caps were tightened down and the gear meshing pattern was nowhere near correct.

I believe the 2.2 and 2.4 gearsets used a different axle housing that put the centerline of the pinion gear in a different location with regards to the ring gear. I don't bvelieve it is physically possible to swap the 3.5 gears into the 2.2 housing. I have tried it with both 8.25 ring gear carriers and the gears sinmply do not line up and mesh.

I believe the 2.7 and up axle housing and ring gear carrier must be used when using 2.7 and up gears. I have a line on an A body 8.25 axle that already has 3.21 gear (and a posi) in it and I am hoping to purchase it and end my rear axle woes. When I get this other 8 1/4 axle, I will take some very careful measurements of the pinion gear centerline on the x and y axis and see if the housings are, in fact, different.

*UPDATE*

I found another 8 1/4 rear axle, this one with 3.21 gears. I measured the 3.21 axle housing and the 2.2 axle housing side by side and I could not determine any difference in the position of the pinion between the two housings. Therefore, I believe my problem with putting the 3.5 gears into the 2.2 housing was either (a) I wasn't doing something right, and/or (b) the 3.5 gear set I got was not for an 8 1/4 axle (even though i bought it at Wildcat and disassembled the donor axle myself).

Anyway, my problem is now solved, and I think I possibly was wrong about there being different axle housings.

I donno…I'm pretty sure there were different axle housings at least for the 7¼". Would have to go swimming in the parts books to check on the 8¼". Anyhow, glad your project's moving forward.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Well, I am big enough to admit it when I am wrong and don't know what I am doing. Alls I can say is nothing I did could get those 3.5 gears to fit properly in that 8 1/4 housing.

DIfferent housings? I can't say. They sure looked identical when I had them side by side and measured. Different carriers? Absolutely.

Dan is right- it will take some deep diving in the old parts books to solve this question.

Reed, is it a Mopar 8 & 1/4 differential?
Just curious.
Glad your project is moving forward.

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"Ja, Ich fahre ein altes auto."
'78 Volare 225
'67 Charger 318

The 2.2 housing is defintely an A body 8 1/4 axle, the 3.2 housing is definitely an 8 1/4 housing, and I am abotu 90% sure that the 3.5 gear axle housing was an 8 1/4 axle out of an early 70s Dodge van.

Now that the 2.2 axle is out form under the car, I may try setting up the gears again one more time just for fun before I try selling it and the extra gear set. Maybe having better access to the axle will help me see what I was doing wrong.