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CJ-7 AMC 20 Axle

pecsxj

pecsxj

NAXJA Forum User
Location
Layton, Utah
Ok before i get hosed here me out.

My brother bought a '79 CJ-7, he is new to the Jeep world and he asked me about his axle's. Well I have never had an AMC 20 so I don't know much about them either. So I figured who best to ask than my knowlegable NAXJA brethren. He recenlty lifted the Jeep and is runnig 33" tires. He want's to go bigger cause it looks kinda funny with all lift he has. So I am wondering how strong this axle is, I have been told that it is as strong as a DANA 44?? Does anyone have any input for me? Thanks in advance for the help/criticism.
 
It is pretty stout if built right. Make sure the axle shafts are not the 2 piece ones that came stock, they will break! My dad broke his 2 piece axle in his 86 Cj-7 with 31's. The ring and pinion are bigger than a dana 44, almost 9 inch ring gear! The axle tubes are kind of weak, a truss would help and you might want to weld the tubes to the pumpkin so they don't rotate if you want it really strong. My dad is running 35's with a detroit and 1 piece shafts. He has not broke a thing since the two piece axle shafts.
 
As jeepboy381 stated, the biggest problem is the 2 piece axle shaft. If it came out of a stock CJ, it believe it has the two piece shaft - which makes it a boat anchor.

With a 1 piece shaft, its not a terrible axle. None the less, its not the BEST option for a swap... just my opinion.

-jm
 
I'd pass. Like has been said 2-piece shaft 20's suck, if it were upgraded, I'm sure he would have told you. If you really want a 20, get one from an FSJ, they had 1 piece shafts and were alot stronger.

I'd hold out for a D44 or 8.8 myself.
 
I don't think he is talking about a swap into an XJ, I believe he is just woundering if this is a good axle for the CJ it is allready in. This should probably get moved to the other tech section because it is not concerning XJ's.
 
it's a good axle if you already have it, or a swap if its already geared the way you want it.. TRUSS IT,wled the tubes and do Moser 1-piece shafts, they have an excellent warrantee, cheap 1-piece shafts are just stock units welded and machined. here's how i did the rear in my CJ5, i also did the D30 front to match. V8 power requires it. :eeks1:

standard.jpg


more pics here of the whole rear axle rebuild.

http://www.fototime.com/inv/C52C4C7930DEE12
 
Hey thanks for all the info. like jeepboy381 said I am not trying to swap it into my jeep. I am just wondering if it is worth it to keep the axle in the CJ or try to get a d44, my brother wants to run 35 12.50. Just trying to see if we need to swap it out or not. thanks again.
 
I wheeled a AMC 20 for years with a SBC and 36s' with Moser shafts and a detroit. My truss ran from flange to flange and captured the housing with a mount from the diff cover bolts. It was the only thing I didn't break! Very strong R&P , OK housing , terrible stock axle shafts.
 
Ditto what the guys have already said. Make sure it has one peice shafts, weld the tubes so the pumpkin doesn't rotate, and truss it good, and it will last pretty well under a CJ.
 
AMC 20 only goes down to 4.56:1 ratio as well. If you don't need lower than that I'd run it after making the appropriate upgrades.
 
Root Moose said:
AMC 20 only goes down to 4.56:1 ratio as well. If you don't need lower than that I'd run it after making the appropriate upgrades.
Click to expand...


Bad info
you can go as low as 4.88 has been that way for years.

YG M20-488 $182.72
High performance Yukon Ring & Pinion gear set for Model 20 in a 4.88 ratio. Yukon exclusively uses 8620 steel in all their Ring & Pinion sets for high strength and long life. They use the latest designs and manufacturing technologies to provide a quiet running gear that is strong and easy to set up. All Yukon Ring & Pinion sets come standard with a one-year warranty.
View More Details
http://www.ringpinion.com/PartsList...Name=Rings+&+Pinions&CatType=Sub-Differential
 
Thanks for all the good info everyone!!
 
Comanchedude said:
Bad info
you can go as low as 4.88 has been that way for years.
Click to expand...

Cool. Good to know.

Any idea when these gears started being produced?
 
If it doesn't already have the one piece shafts, you could add a couple hundred (well, O.K., several hundred) bucks more to what you were gonna spend anyway and do the Warn full floater setup.
 
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