Differential and gears

Differential and gears


Duluth, MN
1982 CJ
I'm having difficulty finding out for sure if I have an AMC20 or a dana. I own an 82 CJ7. I am also having difficulty finding out if it's a wide track or narrow track. I've read that 76-81 are narrow, but I want to find out how to make sure. And I'm also wondering how to figure out the gear ratio without tearing the rear apart. The kid I bought it from wasn't 100% sure but thought it was 3:31.
The rear should be a AMC20. You can tell by the large round differential cover. You should also have wide trac axles. One way to tell the difference between narrow and wide is the shocks mount to the axle tube on wide tracs and they mount to plates under your leaf springs on narrow tracs. Hope that helps.
As far as the gears jack up the rear of the vehicle. Have someone turn the wheel one complete revolution while you count the revolutions of the driveshaft. For 3.55 thre driveshaft should turn 3 1/2 times per one revolution of the wheel.
One more post and maybe I'll get this right :D. The above is if you have a locking differential. If you dont then the number of revolutions would be 1/2 that.
Thanks, it looks like an AMC20. It also appears to be a narrow trac. Thanks for all the help. The stamp on the housing boss just reads B. When I looked it up though, it said that code is only for wide trac. Perhaps these pics will help.
Just so you know I have wide track axles in my 83 and the rear shocks were mounted to the bottom of the spring plate not the axle.
As for the gears why not take the covers off and count teeth? I'm sure the fluid needs changing after all these years.:)
Thanks for the help. The on code the rear axle simply reads B. I've looked this up and it says B is the code used for wide trac. Also, I need to get a new ring and pinion. Is the ring and pinion the same for narrow and wide trac. I just don't want to buy a ring and pinion and have it not work. I'm new to this and I want to do it right.
Same Ring & Pinion, Different axle length.
Rear cover perfectly round and has 12 bolts, It's an AMC20. If it's an odd shape, and has 10 bolts, it's a Dana. Your vehicle came from the factory with a AMC (Spicer) model 20 differential in it.

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