I believe w/ good 2 pieces they compared a amc20 to a ford 9"
It would be able to handle what you're going to give it - pavement / sand.
Truss isn't that expensive to do though / always an improvement / bragging factor.

 

If you look at the dimesnions of an AMC20 against its main competitor a Dana 44 there is no obvious deficiency in its dimensions. The problems are only with the reliability of the 2 piece axle shafts (a dumb design) and a tendency for the axle tubes to spin in relation to the diff.

This axle was used by AMC in muscle cars so it can easily take the power.

If you have:

- one piece axles
- welded the tubes to the diff
- changed the diff lube recently
- installed new oil seals in the ends (i.e. not relying on the 30 year old ones)

then it should be just as reliable as any other axle.

Yes, I know that Dana 60s are sought after etc. but this vehicle will not see the high torque, extreme angles and abuse that a competition machine would.

 

I don't think they are weak as everyone makes them out to be as long as you replace the 2 piece shafts. Welding the tubes/trusses aren't a bad idea either. I haven't managed to tear our's up yet with a 360 in front of it and my heavy right foot.

Example of my driving:

 

Example of my driving:

How do you see where you are going? Have you got a hole drilled in the floor to look out of?

Makes your windscreen wipers redundant. It would also look really good with some chrome on those suspension components. oh, and your headlights will need some changes to their adjustment.

 

My friend had a 83 J10 with a T-176, AMC 20 with 4.10's a warmed over 360 running 14 x35 Gumbo Mudders. This guy had a heavy right foot but surprisingly never broke anything. By comparison, I had a friend who had a 76 J10 Golden Eagle with a stock 360, T-18, D44's with 3.54 gears running Cepek 14/32x15 tires. He broke the rear ring and pinion on the rear 44 twice. The second gearset could have failed because of faulty setup because it ran noisy.

 

Amc20 has a bad rap. The differential btw is the same exact design that Am General used in the H1 Hummer. I found this out from Arb one time when i had to but some seals for my locker. Most of the strength issues come out when people are in low range on rocks. That is by far the toughest wheeling for any axles. Running sand and dirt will be perfect for this axle. I have had two very strong small block chevy motors pushing my jeep with moser axles for ten years now and i like to hammer the gas alot. The only issue i have is the tubes are sagging just abit ajd you will notice that when you outer axles seals always leak. Trussing can stop that.

 

You see a lot of people here that defend the 20, but the reputation for being weak is no myth. For every person who has a 20 that has withstood more than people think it should, i've seen ten that broke under light use.
Sorry, but there is a reason there are different axles, trusses and mods for the 20.....it's because they BREAK.

It it a turd in stock form, compared to ANY axle that is a common swap for it.
A Dana 44 in stock form is superior in every way. Trussing, welding, and 1-piece axles only get you about even, and the 44 still has bigger axles and bearings.

60 is the way to go if you're going to really beat it.

I will say this: Since you haven't broken it so far, no harm in keeping it until you do. I sure wouldn't waste any money/time on trussing it. It's less work to slide a better axle under there.

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i have had good luck, but i plan on swapping to a yj frame and bolting waggy axles to it. im all about preventative measures. that being said, you already have money in your 20, might as well run it. i however do not.

 

Mine has held up fine under my 5.3 on 33's with Moser shafts.

But having said that, when I swap the front axle to a waggy 44 and go SOA, the AMC20 will leaving at the same time for a scout II D44...

 

i have had good luck, but i plan on swapping to a yj frame and bolting waggy axles to it. im all about preventative measures. that being said, you already have money in your 20, might as well run it. i however do not.

This is a valid reason to keep and beef a 20. If you already have axles and a locker, and maybe re-geared, that's when it might be worth it to try and beef it up some.

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I too believe the 20 gets a bad rap, mostly due to general statements. And in it's stock form it is a poor axle design. But as I can tell from reading and from my own experience, it has 3 downsides to it, though all can be overcome to make it a decent reliable axle on par with a 44. A rock crawler it will never be, but then most don't use Jeeps in that capacity.
It's got weak axle shafts and hubs. Fix = new 1 pc. shafts
It's not connected well to the center section and can spin / wrap. Fix = weld the tubes to it
It's got thin walled tubes that can bend. Fix = weld a truss to them

 

I agree on the 1pc axles, and easy to do.
there is a 'notch' hole in the pumpkin that is supposed to have a welded 'plug' to keep it from turning? (I saw the notch, but didn't know).

mine is a narrow axle 79 CJ5, the axle/housing is quite a bit shorter, so less leverage to bend.

But then again, I too don't drive it off cliffs etc.. it would be considered moderate offroading with some rock crawling
(I am trying to keep it in one piece)

 

^Correct on all counts. However, the point I am making is, all those mods only get you almost even with a 44. And if you count up the expense and labor to do them, you are better off, both labor-wise and cost-wise to just slide a Scout 44 under there and be done with it.

This is if you are starting with a stock, unmodified 20.

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^Correct on all counts. However, the point I am making is, all those mods only get you almost even with a 44. And if you count up the expense and labor to do them, you are better off, both labor-wise and cost-wise to just slide a Scout 44 under there and be done with it.

This is if you are starting with a stock, unmodified 20.

Understood.
Tell me this. I've never looked into the scout axle swap path. Is this a direct swap or do you need to cut off the old spring perches and weld on new ones? Same 5 bolt 5 1/2" spread? Curious.

 

I ran my AMC20 until it started to give out. It had one piece axles and I never had a problem, it just wore out. Since I was looking at an expensive rebuild I went and got a D44 from an '86 CJ7 and did the D44 swap while I was at it.

Of course, I'm not a crawler or mudder, just a guy who enjoys 4x4 trails, fishing, the outdoors... so I never really beat it up.

 

Same as some of the others. I ran a 20 in mine for a few years with Moser 1 piece axles and a welded rear. Street driving, sand dunes, and sand drag use. Never had an issue, and only changed because I wanted to run high range, and had a D44 with the gears I wanted sitting there. Mine took A LOT of abuse in the following fashion...

 

Yes, you have to move the spring perches. Can't remember 100% about the wheel pattern, but I think it is the same.

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The scout 44 has the same 5x5.5 lug pattern.

 

but when was the last time somebody saw a scout, more less one in junkyard. when did they stop making scout 1976.

 

Scouts are still pretty easily found being parted out. 1972-1980 Scout II's should all have D44's in the rear and some of the later Scout 800's have the good 30spline, 1pc shaft, rear 44's. I know my 1970 800A has one.

 

Early Scout II's had Dana 30 fronts. The first 1 or 2 years of production as I remember.

 

AMC 20 rear

I have ran the AMC 20 for a long time. as far as a great rearend out of the factory it is not. After one piece axles and a trust they are stronger than a Dana 44. the ring and pinion are bigger which make then stronger. everyone always over looks the size of the ring and pinion. the major difference between a dana 44 and a dana 60, the axle and ring and pinion size, which means a higher spline count. you are already in the AMC 20 so the trust and the one piece axles with a little welding, with your driving you will not need to change to the dana 44 for a long time coming. As for it for competition I have seen them in a lot of poker runs and jeep endurance races as well. this is just my opinion but as far as a rearend that would need no work a Dana 44 is there, but you already have the 20 rearend roll with it you will not be disappionted.

 

Amc 20

My AMC 20 rear end is original in a 1968 390 AMX that has been spinning tires and shaming the big three and foreign challengers for 50 years. No work done and no spun axles. Conventional wisdom isn't.

 

My AMC 20 rear end is original in a 1968 390 AMX that has been spinning tires and shaming the big three and foreign challengers for 50 years. No work done and no spun axles. Conventional wisdom isn't.

You don't have nearly the traction nor the shock loads that a Jeep when offroad puts into the factory 2 piece axle shafts. Spinning tires on pavement is a far cry from spinning a tire in mud/on a rock and then all of the sudden catching traction and shock loading the axle shaft. Nor do you have the same amount of torque multiplication being applied to the axles as a Jeep when in 4 low 1st gear. Apples and oranges here.

 

I keep hearing how weak the AMC 20 is. The weak points being the 2 piece axle and the differential. I installed Moser one piece axles and a Detroit Locker and am running 33's with 4.10 gears in my '84 CJ. So how strong is it now? Why am I asking? Because I am right in the middle of installing a 320-350 hp 5.3 Chevy. I don't do rocks, mostly pavement, 2 tracks and an occasional trip to the Silver Lake dunes, and I hate mud. Never get on it in 4 low and I don't plan on doing any burnouts, well maybe one or two just to see... Max horsepower will be throttling up the dunes. I really don't want to tell the DW that I need to spend another two weeks in the garage and drop another grand or two on a new rear end. I put the Moser axles in 5 years ago when a bearing went out. Never did spin the 2 piece axles in the prior 15 years of moderate 4 wheeling.

The stock front axle may be another issue.

Here is a pic, just test fitting the motor. Man it looks huge compared to the bare chassis.

Actually the AMC20 axle is pretty beefy and strong, the two piece axles is what makes it known as 'weak' I ran 33's on my CJ5 for years, never an issue... but decided to replace them with one piece forged axles. Nothing broke so far (but now of course I jinxed it)

Ron

 

I keep hearing how weak the AMC 20 is. The weak points being the 2 piece axle and the differential. I installed Moser one piece axles and a Detroit Locker and am running 33's with 4.10 gears in my '84 CJ. So how strong is it now? Why am I asking? Because I am right in the middle of installing a 320-350 hp 5.3 Chevy. I don't do rocks, mostly pavement, 2 tracks and an occasional trip to the Silver Lake dunes, and I hate mud. Never get on it in 4 low and I don't plan on doing any burnouts, well maybe one or two just to see... Max horsepower will be throttling up the dunes. I really don't want to tell the DW that I need to spend another two weeks in the garage and drop another grand or two on a new rear end. I put the Moser axles in 5 years ago when a bearing went out. Never did spin the 2 piece axles in the prior 15 years of moderate 4 wheeling.

The stock front axle may be another issue.

Here is a pic, just test fitting the motor. Man it looks huge compared to the bare chassis.

Make no mistake. The AMC20 ring and pinion are comparable to the Dana 60 in size and strength. I believe the faults as discussed can and do happen, but are likely overrated by the mosers and superiors of the world who are there to make money. My AMC20 went 260,000 miles behind a stock 304. It was used for daily driver/mudder/rock crawler as well as snow plow for 15 years before I got it. And then I abused it!! As I have stated elsewhere in the forum, I am going back to the stock two piece setup because I cannot get my single piece setup to stop leaking oil onto both brakes. It is a major source of irritation, especially for something that didn't need to be changed. Error was likely between floor and wrench, but I will update the forum once I find the source of the irritation... ;-)

Great discussion in this thread!!

 

Make no mistake. The AMC20 ring and pinion are comparable to the Dana 60 in size and strength.

The AMC 20 has an 8 7/8" ring gear and a Dana 60 has a 9 3/4" ring gear. Comparable in size and strength?

 

Great discussion everyone.


I've upgraded my AMC 20 to moser 1 piece axles and the CJ7 does great on the rocks and trails here in Western Colorado. My next task for the winter was to have the gears upgraded from the stock 2.73 open differential. My question is two fold.


I like to drive the Jeep on the highway and usually wheel it every weekend. No severe rock crawling, but with the 2.73 gears it's a real dog on the highway with the 33" tires on it. Just had the 258 rebuilt and the transmission is solid as well. I also tow it occassionally behind my RV. So...I'm thinking about putting in 3.73 gears with an ARB locker as some of the trails really need the ability to lock at least 1 axle. Do these lockers cause problems when trying to flat tow the CJ? If I go with the 3.73 gears (has a Dana 30 in the front) I know that should give me a little higher RPM at highway speed so getting up some of the hills should improve. Also plan to have a truss welded on it as well. Anything else I'm missing?

 

Great discussion everyone.

I've upgraded my AMC 20 to moser 1 piece axles and the CJ7 does great on the rocks and trails here in Western Colorado. My next task for the winter was to have the gears upgraded from the stock 2.73 open differential. My question is two fold.

I like to drive the Jeep on the highway and usually wheel it every weekend. No severe rock crawling, but with the 2.73 gears it's a real dog on the highway with the 33" tires on it. Just had the 258 rebuilt and the transmission is solid as well. I also tow it occassionally behind my RV. So...I'm thinking about putting in 3.73 gears with an ARB locker as some of the trails really need the ability to lock at least 1 axle. Do these lockers cause problems when trying to flat tow the CJ? If I go with the 3.73 gears (has a Dana 30 in the front) I know that should give me a little higher RPM at highway speed so getting up some of the hills should improve. Also plan to have a truss welded on it as well. Anything else I'm missing?

Running an ARB rear and Powertrax front in my CJ7. It flat tows fine with the driveshaft removed from the rear driveshaft removed and front hubs unlocked. Note: Dana 300 transfer case. I haven't flat towed locally, but I understand the transfer case is more the issue than the diffs, especially if front hubs unlocked. The way I understand it, with the Dana 300 TC, the oiling action comes from the input end, not the output shafts. To flat tow it with the rear driveshaft connected you are supposed to run the engine with the transmission in gear and the transfer case in neutral every hundred or so miles. That flings oil to the bearings on the output shafts.

So back to the original question, I think you'd be fine with the diffs in any configuration except a lunchbox locker in the rear. Just pay attention to whatever instructions apply with your transmission and transfer case.