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AMC20 - what to do?

walkerhoundvm

walkerhoundvm

Just trying to stay upright
Lifetime Member
City
Cave Creek
State
AZ
All,
I'm having a conniption trying to decide what to do about my differentials, specifically the AMC20.

Some background - I have 2.73 gears and 31" tires currently, and have gone through two transmissions in the past five years, settling on a T176 for now. Seeing as how I don't want to do another transmission swap in the next ten years, I'm shooting to upgrade my differential gearing to 3.73s.

What I have on hand: new Dana 30 carrier and R/P, new AMC20 R/P but no carrier, rebuild kits for both.

My dilemma: finding the larger AMC20 carrier for 3.73 gears. Are there alternatives? Should I consider a locker or specialized differential? Should I do one-piece axles at the same time? What brand is recommended these days? What are my options?

This will be for a 90% daily driver, I don't see this seeing a lot of off-pavement use.

Thanks in advance!
 
For the money of buying gears, carrier, setup and one piece axles, I'd search for an '86 Dana 44 CJ rear. I wouldn't put that much money into a CJ 20.
 
The complicating factors are that I've got a narrow track and I live in the middle of Kansas. We see CJ parts come up about as often as we see a hurricane :(
 
walkerhoundvm said:
The complicating factors are that I've got a narrow track and I live in the middle of Kansas. We see CJ parts come up about as often as we see a hurricane :(
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Narrow track might be easier to find than the wide track. They were in Commandos and some earlier CJs. I actually have one in a set that I've saved for a project. They usually have the larger 11" drum brakes too.
 
The closest one currently is about 4hrs away, in PolarFire's territory. It's got 3.73s, which is a bonus, but probably out of my home range for now :(
 
Have you emailed the Adams boys in Thayer? Or Mike @ 4x4 land? Both stock pretty good inventory and are closer than 4 hours.

KK
 
walkerhoundvm said:
The closest one currently is about 4hrs away, in PolarFire's territory. It's got 3.73s, which is a bonus, but probably out of my home range for now :(
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The Scrambler parts relay sometimes works pretty good. We do it a lot around here.
 
I'd honestly look for a set of 3.31 widetracs. I'm running 31's on all three Jeeps, with 2.73's in the two T176 equipped Jeeps and 3.31's in the T5 equipped Jeep. The 3.31's do fine with 31's, and I recently found a set of 3.31 axles with Superior shafts, lock rights front and rear, and 79 rotors with Warn 6 bolt hubs on the front. Got the front and rear axles for $500 with goodies. I did have to drive about 4 hours each way, but when you look at the time it takes to regear ONE axle, the 8 hours in the car wasn't too bad.

3.31's with a T176 and 31's is a pretty good setup. My plan is to swap an extra T176 in for the T5 on my 3.31 CJ7, and swap a TF999 into the 2.73 equipped CJ7. Have been accumulating parts for awhile, but haven't had time or room in the shop to get into it. Just picked up the 3.31's with lockers last fall, so hoping I can get those swapped in this spring.
 
Since most of what I have is in the 3.73 ballpark, I will probably have to stick that route. I am currently fishing for a Dana 44 with 3.73 gears in narrow track. The backup plan is to build the AMC20 as best I can.

I can fully appreciate the time saving benefits of finding that particular setup vs. building a similar AMC20. One thing I'm worried about is the condition of the Dana 44, but since I'll be buying it already pulled, at least I can have it gone over before installation.
 
What size tires do you plan on running, what type of use will your Scrambler see?
 
Hmm. And what if the chances of it ever going above 65mph are close to zero?
 
walkerhoundvm said:
Hmm. And what if the chances of it ever going above 65mph are close to zero?
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Then 3.73 will be fine:thumbsup:

Just some of my opinions/experiences, everyone is different:twocents::thumbsup:

My first CJ, a '78 CJ-7, came with 3.54 gears, 6 cylinder, and a 3 speed. Those gears coupled with 31" tires was a great match. At the time, I was in high school, so no cross country trips. It had good "get up and go" and still went down the highway well.

I even ran 33" tires with the above set up. Not very good "get up and go", but good highway MPG.

I ran 3.73's with 33" tires and a V8. Very good get up and go, lots of fuel consumed on the highway with no overdrive.

My green Scrambler has 3.31's, T5, and a 30" tires. Good get up and go, gears 1-4. Great MPG in 5th, but no passing power.

"Yard Scrambler"/my now red Scrambler, both had T176's, 258's, 3.31 gears, and 32" tires. This was a great combination for everyday driving, light off road use, and high way use.

Not trying to tell you what to do, just some opinions:cheers::wave:
 
I appreciate it, Spanks. My desire to jump up to 3.73 was based on blowing through T4/T5 transmissions with the 2.73s, I assumed it would be the same with the T176.

Now I feel like I'm trying to justify the 3.73s because that is the shift I'd already started to make. It's hard to go backwards on it now, but if it's the right thing to do...

I'm wondering if it may still be the best choice if I ever go up to 32s, or if the 2.73s will hold up with 31. No matter what, the majority of my driving will be between 15-45mph. Very rarely will it see anything above 65. It's just an around the town vehicle.
 
wm69 said:
I'd honestly look for a set of 3.31 widetracs.
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Agree. So many folks upgrade stock Jeep axles, they are out there. Possibly find a rough jeep, swap axles and sell the Jeep for close to what you have in it.
 
In case anyone is still following - the consensus seems to be that 3.73s may be a bit much, but the sweet spot may be somewhere in the 3.31-3.54 range?

In that case, I still would need to change rear carrier or axles, and would have a load of fresh 3.73 equipment (front carrier for 3.73 and up, front and rear 3.73 R&P) up for sale.

I feel more comfortable now that the 2.73s will last a bit until I can get it figured out. Maybe I'll end up going with a sourced rear Dana 44, and try to swap all my 3.73 gears for 3.54? At least I could stick with the current Dana 30 carrier...
 
Too bad you're not closer...I'll have a set of 3.54 narrow tracks up for sale soon.
 
I have 3.73s with 32s and a t5, and I think it's about right, if I would have changed I'd have gone 411. I don't thing 31s and 373 wouldn't be too bad.
 
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Just in case you find one, an early narrow track D44 from the 70s would need its spring perches cutting off and moving as the chassis is parallel on the pre 76 CJs. May not be a problem to you but something to factor in.
 
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