Model 20 axle question

[elkgroveguy]

I just picked up a model 20 narrow track.
Has 4.10:1 gears, factory Limited slip and 1 piece axles.
The guy I bought it from says it was out of a 1972 CJ5 and the 1 piece axles were factory?
I have never heard of factory model 20 one pice narrow track axles?
Does any one have any info on these axle shafts?
Also does anyone have any info on rebuilding a AMC Limited slip?
Thanks!

 

[jp360cj]

I just picked up a model 20 narrow track.
Has 4.10:1 gears, factory Limited slip and 1 piece axles.
The guy I bought it from says it was out of a 1972 CJ5 and the 1 piece axles were factory?
I have never heard of factory model 20 one pice narrow track axles?
Does any one have any info on these axle shafts?
Also does anyone have any info on rebuilding a AMC Limited slip?
Thanks!

Do you have a picture?

The only AMC20 I'm aware of that came with factory 1-piece shafts were in FSJ for a few years in the 80s. Those were wider than even widetrack CJs (~58" WMS for the narrowest FSJ rears) and were 6 lug.

The AMC20 didn't come in '72 CJ5s. Those used a narrow track Dana 44 with 1 factory 1 piece shafts. These were the same width as a NT AMC20 & 5x5.5" lug pattern, but the spring perches will need to be moved outward to fit under a '76+ CJ.

A 72-73 Commando had the same 1 piece, NT Dana 44 rear as the 72-75 CJ, but the Commando rears have the same spring perch spacing as a '76+CJ.

I don't know what gears were common in the commando, but the '72-75 CJs were either 3.73 or 4.27 gears from the factory. A narrow track AMC20 could have been 2.72, 3.31, 3.54, or 4.10, depending on the year.

I would definitely check the gear ratio before going much farther. As for rebuilding the factory Limited slip, I wouldn't bother. I would swap it out for a Trutrac instead.

 

[Lumpy Grits]

'72 CJ did not have the 20 rear.
No CJ with the 20 rear, had 1-piece axles as OEM.
That 'guy', is either ignorant or lying to you.
You better open it up to see if it is even a 4:10 w/LSD.
Can you post a few pictures?
LG

 

[elkgroveguy]

I opened it up before I bought it.
41 teeth on ring gear, 10 on pinion (4.1:1 ratio)
stock Limited slip clutch pack carrier.
another thing I also noticed is there are grease nipple in the axle housing close to the edge of the axle tube.

 

[jp360cj]

I opened it up before I bought it.
41 teeth on ring gear, 10 on pinion (4.1:1 ratio)
stock Limited slip clutch pack carrier.
another thing I also noticed is there are grease nipple in the axle housing close to the edge of the axle tube.

I've never seen those grease nipple from the factory (at least not on any Dana 44 or AMC20). If it's on both sides (driver/passenger), then it may have been drilled and tapped for the grease fittings in order to help grease the wheel bearings.

Is the cover round (like a 1/2 sphere)? If so, then it's an AMC20 with aftermarket shafts and the guy you bought it from just doesn't know what it came out of. But do measure the spring perch width. The 76+ CJs had ~36" perch width. The 72-75 CJs had a narrower perch width (don't know the exact measurement, but probably ~6" narrower from what I recall), just in case it was swapped into a 72-75 CJ. This would be an unusual swap, but I know how us Jeepers can be!

 

[elkgroveguy]

I have not measured the spring perches yet.
I expect the perches to be narrower than mine, I already have new ones to weld on.
It is a AMC20 rear, Dana 30 front.
My guess is that some one put aftermarket axles in and added the grease fittings, but I also know amc did weird **** throughout the years so I thought I would ask.
But I got both axles for $500, gears look good, in both, Detroit in front, and 1 piece axles in rear, I felt it was a pretty good deal.

 

[jp360cj]

Yeah, sounds like it to me too. That's a pretty good deal with the gears and detroit. Hell, the detroit itself would cost you more than that. Really, the only downfall (IMO) is the NT width, but that's not really a big deal.

Just curious, is the front a drum or disc brake?

 

[elkgroveguy]

Disk brake front.
Who knows maybe I will measure the perches and find them to fit my jeep.
This guy had like 20 axles at his house, he buys and parts out jeeps.
maybe he forgot what they were off from.

 

[elkgroveguy]

Well I think the guy I bought this from forgot what they were out of.
I measured the spring perches and they are the same as my 1979 CJ5!
So good news is I don’t have to move the spring perches!
I’m just putting in new u joints up front and disassembling and regreasing everything.
I’m also turning the front rotors and rear drums with new pads and shoes!
Hopefully get these put under the Jeep in the next couple of weeks!

 

[gert]

section 10 page 32 is the factory trac lock

https://www.jeep-cj.com/jeeplinks/great-jeep-cj-tips-18/jeep-1976-tsm-online-115/

 

[jp360cj]

Well I think the guy I bought this from forgot what they were out of.
I measured the spring perches and they are the same as my 1979 CJ5!
So good news is I don’t have to move the spring perches!
I’m just putting in new u joints up front and disassembling and regreasing everything.
I’m also turning the front rotors and rear drums with new pads and shoes!
Hopefully get these put under the Jeep in the next couple of weeks!

That's good to hear...I've got several parts I've acquired that I don't remember exactly which ones came from which Jeep too. Should be a fairly easy swap (assuming everything comes apart ok).

You may be planning on doing this anyway, but I would also replace the springs/cables/adjusters on those drums brakes.

 

[elkgroveguy]

section 10 page 32 is the factory trac lock

https://www.jeep-cj.com/jeeplinks/great-jeep-cj-tips-18/jeep-1976-tsm-online-115/

Thanks!
Super Helpful!

 

[elkgroveguy]

That's good to hear...I've got several parts I've acquired that I don't remember exactly which ones came from which Jeep too. Should be a fairly easy swap (assuming everything comes apart ok).

You may be planning on doing this anyway, but I would also replace the springs/cables/adjusters on those drums brakes.

Im actually going to do new wheel cylinders and hardware kit!

 

[Turbogus]

Hopefully before you go with any great expense make certain that the axle tubes are straight and true. When i first got 'BB' this was her biggest problem and it wasn't discernable when mounted up. It was only after dumping a bunch of clams on it then after getting it on the ground did we see one of the axle tubes was bent. It played hell with bearings and shaft wear.

 

[elkgroveguy]

I got the axles installed this weekend.
Front is perfect, but the rear has a slight leak from the pinion seal.
So I will change the pinion seal and should be good to go.
The gear ratio seams perfect for me, with the T-18 and Dana 20.