Rear diff replacement?

I had a hub spin on an AMC 15 torque tube diff because I never knew to re-torque it. It was changed to an AMC 20 with 9" brakes and 1 1/4" axles. I had no trouble with that one but changed it to one with 10" brakes and 1 3/8" axles. It has a slight pinion seal leak that I have to top off every year. I really should have changed that seal when I had it out to change carrier bearings. One thing I will say about the AMC 20, at least the T/T type, is that it is darned heavy.

I bought a big size 82 Jeep Cherokee that I found out had a leaking pinion seal because the nut had backed off. A new seal and a new nut staked so it couldn't come off again fixed that. 

I can't say i am a big fan of the the AMC differentials but I have also had trouble with others. The GM 10 and 12 bolt use the axles for the bearing surfaces which present their own set of problems.

Chocks are probably better than a park brake, but inconvenient to use a lot. There are plenty options for park brakes though. A go-cart mechanical caliper is great for a park brake. Will hold a non-moving car, but won't slow it if powered. So make sure you have a brake warning light. Hard to make two work off a single cable, but can be done. Or mount a small disc on the pinion and use there... but hard to mount caliper on diff.

I'd say the noise you have is from the old gears. Probably didn't change any seals when he swapped axle, maybe pinion seal, and it's at least 30 years old. 30 year old seals leaking is no surprise, even if they were brand new (NOS). Sitting hurts more than moving, you probably know that!

A newer D35 from an XJ Cherokee fits, shock mounts need to be changed around though... I think just one side. They are a bit stronger than the AMC 15, mainly due to one piece hub/axle, but I think the axle shafts are slightly larger also. Diff design is the same. I don't know if the front diff gears would interchange or not. Both are Dana 30 though....

It depends on the year. Our front axles are low pinion and everything after our stuff is high pinion. Pretty sure this is the reason the throwout fork for our T-5s are high.It's probably the pinion seal or the cover. Ugh...I just really dread messing with this thing. Almost as much as brakes.

I don't know about your particular AMC, but I dropped a Mopar A Body 8.75 rear into out Gremlin. It fit the perches like it was made for the car. Only problem was the axle tubes were much larger in diameter than the original AMC 15 rear, so I had to have custom U-bolts made to mount it. Also had to take it to a good brake shop to get E-brake cables that would work with the AMC cable from the front.

DaemonForce wrote: Mopar 8¾" rear in a Gremlin?! Now THAT sounds like a good idea! If I remember the Chrysler New Yorker builds, that was a dropout carrier that would be easier to work on at the bench rather than under a big heavy car.

Yes, and the third member is a ":quick change" unit, so changing gears is quite easy. I've already run 2.76, 3.55, and 3.23 (currently) in the car.