-
Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.
AMC 20?
- Thread starter xjrider95
- Start date
- Location
- Minneapolis, MN
Depends on what it came out of.
Watcha trying to do by swappin in a different axle ? Give us some specifics on where you are going with this idea.
IllianaXJ
NAXJA Forum User
- Location
- Southwest IN
Macgyvr has one in the rear of his buggy, seems to work pretty well. Check his build thread in Advanced Fab.
igotanxj
NAXJA Forum User
- Location
- Citrus heights
its supposed to be a pretty good axle, they come with 2 piece axle shafts which are the weak point, but once you change those to solid 1 piece axle shafts they are about as strong as a D44 from what I hear.
toplessxj89
NAXJA Forum User
- Location
- south jersey
they are very strong with after market one peace shafts we have an amc 20 in our cj with a spool and 37's and it holds up great
ChicksDigWagons
NAXJA Forum User
- Location
- Upper Michigan
Not all AMC20s came with Two peice axles, those were limited to the CJs IIRC. The Fullsize Jeeps used an AMC20 rear for many years, essentially a "waggy" axle except not a D44.
Even the familiar MJ used an AMC20 rear as part of a towing package or something.
Take it all with a grain of salt but this is from memory. The real thing to watch for with the AMC20s was spinning the axle tubes. Nothing a full weld wouldn't handle. If you can get one for free or cheap from an MJ or SJ, I'd definitely consider running one under an XJ. If it comes from an SJ though realize the bolt pattern will be different, but the front axle from the donor would make a good candidate for a swap as well.
Even the familiar MJ used an AMC20 rear as part of a towing package or something.
Take it all with a grain of salt but this is from memory. The real thing to watch for with the AMC20s was spinning the axle tubes. Nothing a full weld wouldn't handle. If you can get one for free or cheap from an MJ or SJ, I'd definitely consider running one under an XJ. If it comes from an SJ though realize the bolt pattern will be different, but the front axle from the donor would make a good candidate for a swap as well.
scottmcneal
NAXJA Forum User
- Location
- not here
I would buy it..
squirrel80
NAXJA Forum User
- Location
- Prescott Valley, AZ
My biggest concern would be how narrow it would be for an XJ unless you plan on swapping the axle tubes. Which would be a good idea since they are one of the weak points. Seams like a lot of work when there is a lot of Dana 44s out there.
Here is some info:
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 OpenDD 2.73 Trac-LokBB 3.31 OpenCC 3.31 Trac-LokA 3.54 OpenN 3.54 Trac-LokGG 3.73 OpenQ 3.73 Trac-LokL 4.10 OpenM 4.10 Trac-LokWide Track AMC 20 Code Gear Ratio Diff Type D 2.73 OpenDD 2.73 Trac-LokB 3.31 OpenBB 3.31 Trac-LokA 3.54 OpenAA 3.54 Trac-LokH 3.73 OpenHH 3.73 Trac-LokC 4.10 OpenCC 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 YearsAMC 20/CJ Narrow Track 36" 50.5" '76-'81AMC 20/CJ Wide Track 36" 54.5" '82-'86AMC 20/SJ Narrow Track AMC 20/SJ Wide Track
Here is some info:
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 OpenDD 2.73 Trac-LokBB 3.31 OpenCC 3.31 Trac-LokA 3.54 OpenN 3.54 Trac-LokGG 3.73 OpenQ 3.73 Trac-LokL 4.10 OpenM 4.10 Trac-LokWide Track AMC 20 Code Gear Ratio Diff Type D 2.73 OpenDD 2.73 Trac-LokB 3.31 OpenBB 3.31 Trac-LokA 3.54 OpenAA 3.54 Trac-LokH 3.73 OpenHH 3.73 Trac-LokC 4.10 OpenCC 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 YearsAMC 20/CJ Narrow Track 36" 50.5" '76-'81AMC 20/CJ Wide Track 36" 54.5" '82-'86AMC 20/SJ Narrow Track AMC 20/SJ Wide Track
squirrel80
NAXJA Forum User
- Location
- Prescott Valley, AZ
He is running an Eaton rear end which is alot bigger than a Dana 20.
Narrow Track is 50.5" wide
Wide Track is 54.5" wide
XJ is 61" wide
squirrel80
NAXJA Forum User
- Location
- Prescott Valley, AZ
Nope 36" is spring pad to spring pad. Sorry but the AMC 20 is a pretty narrow axle compaired to the XJ. You have to remember all the backspacing that the XJ has on a stock wheel. Keep your eyes open for a Dana 44 from an XJ and make it a lot easier on yourself. Or if you need something bigger there is always full width Dana 60s and 14 bolts.
- Location
- Columbus, In
Doesn't Gene have one under his ZJ?
Mike H.
NAXJA Forum User
- Location
- phoenix az
In the SJ world, folks like the d44 over the 20.
Personally, I think you'd be better off with an 8.25, 8.8 or d44 as they would be cheaper in the end.
Personally, I think you'd be better off with an 8.25, 8.8 or d44 as they would be cheaper in the end.
