tell me about the amc 20

[92islander]

i recently came to be in possession of an amc 20 rear axle. this axle isnt the weeker two piece axle so i was wondering if it was worth puting under my yj or if i should keep looking for a D44?

[chad huff]

I have an AMC 20 in my scrambler with moser shafts and a lockright.So far no problems on 35s and currently on 37in krawlers with several trips to Tellico.But I am switching it out for a Ford nine with parts bought on Ebay and w/Strange axles, Way stronger than a dana 44 and cheaper to build

[KaiserJeepMan]

Is it from a full size Jeep? or is it from a CJ with after market flanged shafts? If it's from a FSJ then it's actually a AMC M23. They came with flanged shafts from the factory and are 6 lug. M23's are actually a little stronger then Dana 44's, since they have a larger ring gear. 8 7/8" iirc. They have 29 spline shafts (vs the 44's 30), but 1 spline doesn't make any real differance. Only real draw back is that you can't gear them as low as you can a 44. Pretty sure they have beefier tubes then the M20 as well.

[CJim7]

Corp 20 R&P is slightly larger then a D44 R&P. Where the 20 loses its glamor is the 2pc design along with thin axle tubes and tendancy to spin in the houseing. All of this, of course, can be remedied useing 1pc shafts, trussing, and welding the tubes.

I was under the impression the FSJ used a corp 20 with thicker tubes being the big difference. never heard of a m23:confused:

[rustywagoneersdotcom]

M23 is the technically correct designation for the FSJ version of the AMC model 20 axle.

they all have one-piece axles
thicker axle tubes.
and the main thing is that the pinion bearings are D60 size, meaning the pinion gear doesnt walk around as much as a 44, and the 'stem' or shaft of the pinion gear is that much stronger against rotational loads... and yes, the ring gear is larger than the D44 (8.875 vs 8.5)

so, again, is this axle out of an FSJ, or is it a CJ axle with one-piece shafts?

peace
Dave

[Balsax]

... the main thing is that the pinion bearings are D60 size, meaning the pinion gear doesnt walk around as much as a 44, and the 'stem' or shaft of the pinion gear is that much stronger against rotational loads...

So, excuse my ignorance, but does that mean that those versions of the M20 (m23) use a different R&P?

[92islander]

the axle is out of a 1980 j-10 if that helps any.

[learfxr]

That's a FSJ. I have the same axle on my 82 J10. That's what they were asking. The CJ's and FSJ's both used the 20. The CJ version is narrow if I remember right, that's why they asked.

[KaiserJeepMan]

the axle is out of a 1980 j-10 if that helps any.

Then it's a M23 with all of the good qualities mentioned above. Stronger then a D44 rear. Stick it under your Wrangler and wheel it. They hold up decently with large tires, and I'm talking under 5500lb FSJ's. Should do great under a Wrangler.

[rustywagoneersdotcom]

....does that mean that those versions of the M20 (m23) use a different R&P?

nah, all variants of the M20 use the same basic R+P,
The pinion and pinion bearing comments were D44 to M20 comparisons...
the thicker tubes / 1-piece axle stuff is FSJ versus CJs & cars

peace
Dave

[Haggar]

yep, the model 20 diffs themselves are quite strong, It was just the CJ housing/tubes, and axleshafts that caused the bad rep.

The model 20 diff is also used in the H1 hummers.

With the J-truck version, it should hold up quite well.