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Rear end help

V

Valntino

Basic User
City
Bedford Hills
State
NY
Hello all,
I have an 85 with a 258/4 speed.
How can I tell what Rear is in it?

Thanks!
 
Is its the factory rear end, its am AMC 20. What's more important is the ration. Look for a tag on the front axle dif cover bolts.
 
Also should be a stamp right next to diff cover on AMC 20... A AA B BB codes
 
The "stamp" is here...

AMC20-gear-ratio-2[1].jpg

Translation is here (for wide track AMC-20s): BUT -- that just means that what AMC shipped... no telling what's in there 30 years later...


Code
Gear Ratio Diff Type


D
2.73 Open

DD
2.73 Trac-Lok

B
3.31 Open

BB
3.31 Trac-Lok

A
3.54 Open

AA
3.54 Trac-Lok

H
3.73 Open

HH
3.73 Trac-Lok

C
4.10 Open

CC
4.10 Trac-Lok
 
b2esq thank you for the ID info for the wide track rear ends. Checked my cars and parts to see what I have. My wife's 81 Scrambler (narrow track) had AA so I guess that is a 3.54 trac-lok same as the wide track would be. Looks like the rears from cjs with automatics were D or 2.73 open. Four cylinder cjs had B or 3.31 open. I have a BB that came out of an 82 Laredo and the gears from the front dif that went with it. Does the trac-lok perform noticably better in the mud or snow than the open ones? Are there any marking on the front AMC 30s that identify them?
 
Dana 30 had a tag on the front diff cover held on by diff cover bolt. Gear ratio is stamped on the tag
 
Does anybody have any AMC literature that explains how the Trac-Loc works? Before this post I didn't know AMC offered a type of locker for the dif.
 
Kim Dawson said:
Does anybody have any AMC literature that explains how the Trac-Loc works? Before this post I didn't know AMC offered a type of locker for the dif.
Click to expand...

It is NOT a true "locker", just a clutch driven limited slip, similar to a GM "posi-trac" :thumbsup:
 
When new they work ok, but the clutches wear out pretty quickly and then you have basically an open diff.

Here's an excellent AMC20 rebuild thread on a trac-loc diff (with lots of pics)

http://www.jeepforum.com/forum/f8/full-amc-20-rebuild-setup-1176780/

From what I've seen, T176's usually got 2.73's, and T5's got 3.31's in the 80's. Very general rule of thumb, but most (not all) I've seen follow that pattern.
 
wm69 said:
When new they work ok, but the clutches wear out pretty quickly and then you have basically an open diff.

Here's an excellent AMC20 rebuild thread on a trac-loc diff (with lots of pics)

http://www.jeepforum.com/forum/f8/full-amc-20-rebuild-setup-1176780/

From what I've seen, T176's usually got 2.73's, and T5's got 3.31's in the 80's. Very general rule of thumb, but most (not all) I've seen follow that pattern.
Click to expand...

Thanks for the info and the link.
 
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