amc20 ????

[mmcj7]

I was wheel-in at the flats today before my cj died and I thought the tires were rubbing the frame mounts. I have a 3" body lift with a 2" spring lift With 35's on 15x10 wheels. Its been set-up for a while but only used as a DD. Well after I got it straightened out tonight I pulled it up to some rough terrain in low with my front hubs unlocked. As soon as I let the clutch out it popped a few times on each side and then it seemed locked in and worked fine. I crossed it up several differant ways and it didn't make any more noise. So I'm guessing it was the diff or the 2 pc axles. I wheeled it for about 1 hour pretty hard and it seemed fine. Any Ideas?

 

[ol'Jeeps]

My 2 pc axles pop constantly! But my rear is welded, so I guessed its just binding coupled with some end play in the axles. Never has show to be any problems with the taper or the key. So I just ignore it!

 

[BigJUGGY]

If our old CJ "DIDN"T" pop & creek, bind, grind & shutter...I would think something was Broke...I say just go on with it...till she can't take anymore Captain'...

 

[mmcj7]

Its been a tough one but the way everyone talks about the amc 20 I thought it would only be a matter of time before it craps out. I was speed shifting from 1st to 2nd and twisted the rear drive shaft in a knot and the amc20 still seams ok. I've got a set of wide tracks to go under it but its still the amc20 and D30.

 

[Caver Dave]

I thought it would only be a matter of time before it craps out

As long as you understand the "issues" with the M20 in stock form combined with high HP/torque/traction/locker:
+ The ring gear is comparable to a D44 & decently sized for larger tires, but...
- 2pc axles die when the shaft spins inside the hub (fix = 1pc axles)
- The axle tubes aren't very beefy & prone to bending (fix: some sleeve them & some run a truss along the backside)
- The axle tubes aren't secured to the chunk very well (press fit?), brings the big suck when the chunk spins up (independent of the tubes which are secure by the perches/u-bolts) & shreds the driveshaft/u-joint at the pinion (fix = stitch weld the tubes to the chunk)
... they can be modified to handle the abuse!

 

[Schardein]

My experiences with about 100,000 miles of AMC 20 use:

Burned up a passenger side bearing about a month after a deep water crossing. Could happen to any axle. When I say burnt up, I mean total failure, bearing rollers were gone, heat melted the plastic axle nut cover used on the later CJs... it literally melted and plopped on the ground as I stood looking at it.

Took the opportunity to upgrade to one piece axles.

About a year and half later, the driver side bearing on the one piece axle shaft "walked" about a half inch out, allowing the splines to disengage at the diff. Since I had a traclok, no locker, it was like being in neutral. Had to put it in four wheel drive to get home, wondering the whole way how loose the bearing was and if the wheel/tire/axle was going to come sliding out. Made it home. Replaced the bearing and press on lock ring on that side only and never had any more problems.

Replaced with a D44 at about 215,000 miles on the Jeep.

 

[mmcj7]

- The axle tubes aren't secured to the chunk very well (press fit?), brings the big suck when the chunk spins up (independent of the tubes which are secure by the perches/u-bolts) & shreds the driveshaft/u-joint at the pinion (fix = stitch weld the tubes to the chunk)

So the tubes are only pressed in I will be sure to weld the wide track 20 when I put it in this fall. When you say truss the axle would that be over the diff and extend to the perches?
Thanks for all the help so far guys.

 

[RenegadeT]

Make sure the bigass nut that holds the axleshaft to the hub is tight, the factory spec is on the order of 3500 ft-lbs. If it spins, and you have an open carrier, you WILL know it spun, because you won't go anywhere in 2wd.
I had someone stitch weld my tubes to the pumpkin, I guess that helped, cuz they never spun. I had no truss and my widetrack amc20 finally bent. I had ECGS truss my replacement widetrack, but still havent got around to installing it.

 

[amcjeepman]

Here is the over the tube truss on my wide trac M20

,
It has held up to 38's till I went to 36" iroks.
I wheeled a 2 piece factory axled m20 w/35's for years w/ no failures. It was locked w/ 4.11's. The key to 2 piece axles is proper torque on the nut (250 ft lbs.) after the 1 5/16 dimension from the face of the hub to the end of the axle is achieved. I have seen a couple twist the tubes but never had it happen to me. I don't like 1 piece axle in a 20 so I went full float.

 

[Caver Dave]

My experiences with about 100,000 miles of AMC 20 use:
Burned up a passenger side bearing about a month after a deep water crossing.

Tater burned up a couple bearings over the years. After we replaced a single hub (even though it was spinning, took an 80T press to get the shaft out of the old one, took the 3500#/ft Tony spoke of to get the 250#/ft final).... went to 1pc axles after that, has since had a re-gear & spool (Raleigh 4WP) & had the tubes stitched shortly afterwards.

 

[mmcj7]

I think I figured out the noise, when I got home yesterday I pulled it into a ditch and turned the back wheels over and it made the same noise again. So I parked it and got up under it and it looks like the u-bolts have worked loose letting the axle rock about 1/8".