8.75 help!!!!

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petethekiller

petethekiller

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Ok my brain is smoking and I am at a total loss....

I purchased Nitro axles shafts with Green style bearings for my A body 8.75 rear end with a clutch type limited slip diff... I have 2 741 cases with a 3.91 clutch type diff one which was previously installed and driving with a howl but fully functional.

I purchased the second 741 case built the same way used but functional. I installed the newly purchased diff with the factory style axles and bearings to load the car on a trailer without any issue. I relocate the car and install the new axles with the green bearings which required me to remove the thrust bearing from the noted diff.

After installing the new axles with the green bearings I slowly drove the car in reverse 10 feet and heard a loud pop. At this point I had not movement as the driveshaft would spin but the differential would not so I assumed either the pinion popped or the axles did not fully engage the diff. I pulled the diff, swapped in the old diff and again the new axles shafts... Same results. Back up and a pop resulting in no movement though being driven by the driveshaft. When pulled the diff, no visible damage to either the axles or the diff.

I measured both axle sets of
shafts and they measure the same length so I am at a loss here.

What am I missing?
 
I'm thinking somehow, the difference in bearings is keeping the axles from engaging the splines in the pumpkin. I would endeavor to take measurements. Not sure exactly "how" but one way would be to drain oil, remove axles, and "stick" (carefully) to get an accurate depth from a known point on the axle housing flange to a repeatable point into the differential. Then remove pumpkin, install axles, and measure between them with them fully seated. From that you should be able to "diddle around" and determine where the axles are sitting in there

If that gives you no result, I would say tearing down the differential and a close inspection is the only other route
 
A-bodies IIRC are speced at around 52/52.5
EDIT: a lil research showed up 52.625
That would make your new axles 1.0 + .25= 1.25 inches too short.....

Your spec is for a 65 to 67 B-body, which is a common swap, altho it can be tricky to mount wide wheels.
 
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petethekiller said:
It measures 54.625 flange to flange. that being said the new axles are .25 shorter than the ones I pulled out.
Click to expand...
Then that's not an A body rear end. A bodies are 52 5/8 flange to flange.
An accurate 8 3/4" rear axle width list | For A Bodies Only Mopar Forum
Your width puts the housing as a B body (allowing for measuring discrepancies), a smidge over 2" wider than an A body rear.
If you originally had A body axles in there (small bolt pattern), then the splines were just barely engaging, as evidenced by the new axles (1/4 inch shorter) not engaging. That means your old axles were only engaged by 1/4 inch!
Long story short, you need either longer B body axles or an A body housing.

Edit: Okay, now you edited your original post to say 52.625 instead of 54.625 flange to flange. Which is it?
 
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If I understand this correctly, and the axles did come loose from the diff, with the weight of the vehicle on them those bearings are now trash.

Can you install diff and one axle, and measure with a steel rod or broom handle or something to see where the axle protrusion is into the diff?
 
Sounds like you have an A body housing. But it sounds like your axles are barely long enough and are just slightly engaging in the inner clutch hub.
 
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