Jeep CJ 7 problems Dana 30 and AMC 20

the rear axle front pinion DANA 44 or AMC?
the answer is not simple , why not read the FSM and unstand it all.
experpted....

1. On 1990-98 models, set bearing preload as follows:
   1. The required pinion gear bearing preload torque is 1/2 ft. lbs. over the noted release torque as measured above.
   2. Rotate the pinion gear three or four times with a torque wrench attached to the yoke nut. Measure the amount of torque necessary to rotate the pinion.
   3. Using a holding tool, tighten the yoke nut in small increments and remeasure until the specified torque is obtained.

$15
alldata.com
or
free
here
http://www.jeep4x4center.com/knowledge-base/index.htm?utm_source=cj#service
see diff chapters. its non trivial.

the bell housing might be different

It depends on your transfer case

spicer 18 and 20 takes 80W-90 gear oil
dana 300 takes 85W-90 gear oil.

I personally don't think it would matter either way if you put 85 or 80. They both lube well. Thats my opinion.

Dextron III ATF (automatic transmission fluid) will work in this transfere case just fine

I would check the carburator. Can you keep it running with starter fluid?

The last Cj-7 was built in 1986. And they didn't come factory with a V-8 so you have a conversion of some type. Most factory wiring diagrams aren't going to help much. Sorry

Jeep Axle: AMC 20

Front Axles
Dana 44
Dana 30
Dana 27
Dana 25


Rear Axles
Chrysler 8.25"
Dana 35c
AMC 20
Dana 30
Dana 60
Dana 53
Dana 44
Timken
Dana 41
Dana 23


Jeep Axles
Upgrades
Factory Options
General


-->All AMC 20s have a 8 7/8" R&P and use a 29 spline shafts. The AMC 20 R&P is 3/8" bigger than the Dana 44, but it uses smaller shafts, smaller axle tubes, and the CJ version comes with weaker two piece shafts. The AMC20 uses a 29 spline shaft where as the later Dana 44 uses a 30 spline shaft. The AMC 20 housing tends to flex a lot which can cause breakage. This can be remedied by welding the tubes and/or adding gussets. The reason the AMC 20 flexes more than the Dana 44 is the shorter differential housing and smaller axle tubes. It's other flaw is the CJ version uses the two piece axle made up of a hub and a shaft. The hub end tends to break off under load which has created the market for one piece AMC 20 axle shafts. Unfortunately, the shafts are expensive ($350+ USD) and in some cases a special bearing must be used.
-->Identifying the gear ratio of an AMC 20 is a bit tricky. Dana axles normally have a tag on the left of the diff cover with the gear ratio at the time of build. The AMC axles have a code that has to be looked up in a table. The code is stamped on the housing boss to the left of the diff cover right near the axle tube. Good part about the stamp is it tends to stay readable longer than the tag, but you have to know the code. Since there are conflicts between what a code means for a narrow track and what it means for a wide track, don't count solely on the code to identify an axle. Bring a tape measure or know the source of the part. Specs Narrow Track AMC 20 Code Gear Ratio Diff Type AA 2.73 Open DD 2.73 Trac-Lok BB 3.31 Open CC 3.31 Trac-Lok A 3.54 Open N 3.54 Trac-Lok GG 3.73 Open Q 3.73 Trac-Lok L 4.10 Open M 4.10 Trac-Lok Wide Track AMC 20 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-LokThe Trac-Lok is a limited slip differential. You may have to scrape away a lot of mud, paint, and rust to uncover the code. If you can't find the code on the rear, check the tag on the front axle. Both axles should be geared the same. The R&P ratio ranges supported by the carriers are 2.73 and 3.31-5.13. The 5.13 gear ratio is not available for the Dana 30 though, so it is rare to see it. 4.56s are the lowest common ratio between the Dana 30 and AMC 20. 5.13s are available for the Dana 44.
CJ AMC 20 The CJs used two versions of the AMC 20, the narrow track from '76-'81 and the wide track from '82-'86. Both versions use keyed, two piece shaft/hub design and 5 on 5.5" wheel bolt pattern. Supplies of AMC 20s were exhausted in 1986 and some Dana 44s were used instead in the last of the CJ-7s.
From 1976-1978 a larger 11x2" drum brakes was used on the AMC 20. After 1978, a 10x1.75" drum was used.
SJ AMC 20 The Wagoneer and full size Cherokee also used a narrow and wide track version of the AMC 20. Both SJ versions used once piece shafts and 6 on 5.5" wheel bolt pattern. Since the length and bolt pattern is different from the CJ version, the SJ shafts are not compatible without resplining and redrilling. I've never heard of anyone going to the trouble.
Model/Version Spring Pads Wheel to Wheel Years AMC 20/CJ Narrow Track 36" 50.5" '76-'81 AMC 20/CJ Wide Track 36" 54.5" '82-'86 AMC 20/SJ Narrow Track AMC 20/SJ Wide Track Last modified Friday, 03-Dec-1999 21:48:34 MST
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Yuo deifinitely have to get rid of one differential to match the other. I would change the rear diff as the gearing in that one will give you really poor mileage... additionally welded spider gears (poor mans positraction) make cornering a nightmare (the outside wheel must turn faster than the inner one on turns, which is why no one uses "spool" type differentials on anything but drag race vehicles (because they only go in straight lines).
As far as which Dana unit you are supposed to have, YOU MUST MATCH THE EXACT GEAR RATIO TO THE FRONT UNIT or, it will destroy the transfer case!!! You could even modify a chevy or ford diff to fit under there, but the ratio match has to be exact!!! To find ratio, count the ring gear teeth and the pinion gear teeth. I don't remember the formula but you need to establish a ratio from these two #s.(divide the ring gear# by the pinion#??? answer is expressed as (answer:1 such as 3.23:1))

if you alter the steering and suspension in any way as far as changing factory settings you need to get an alingment it sounds like you have to much negative caster

try a drop pitman arm.