amc 20 gearing

[MIDLERTH]

I am running amc 20 front and rear with what I think are 2.73's. Seams way to high geared for 33's and a beefy ch. 350. Looking for some advice on what to gear down to 4.27 or 4.56? Any other options that i dont know about. :confused:

[netbear]

I would think your front axle is a good
old Dana 44. The Rear AMC 20 in a FSJ is
a decent axle also for 33" tires. For all
around use I would go with 4.11 gears. This
will give you a huge increase in on and off
road performance and not wind the engine too
hard on the highway.

[Max Power]

Not sure what year you've got, but I'm pretty sure the carrier will accept up to 3.73, after that you've got to change carriers. {mo $$} 3.73 will give you decent crawl and hi-way manners w/ a 32 and maybe a 33 n tire.

I've got 3.31 and 31in tires and its ok, but I wouldn't want to goto a larger tire w/out lowering the gears, well..... maybe a 32in.

good luck

[Stuka]

From what I know (not for sure on this) is if you have 2.73 gears, you need a new carrier to go over 3.07. If you have 3.31 gears, then you can go all the way up to 4.56.

[Cliff]

Ditto on the new carrier. I have 2.73's and am replacing the carrier to install 3.54 gears. The Dana does not need a new carrier.

[robselina]

I've got 31s running on the stock 2.73s. It works, could have gone 32s I think, 33s maybe. Depends if you have an auto or a manual. You can get away with worse gearing on an auto since you can ride your brake if you really have to. You might just want to consider swapping your axles though, instead of regearing. You can find axles relatively cheap if you look around and are patient. It's a LOT cheaper than regearing I think, at least for the rear. Front is more complicated, so it could add up quick I bet. Even so, good axles are available for $100-$200 with 3.73-4.56 gear ratios and you don't have to deal with an R&P swap AND you can get a heavier duty axle at the same time if you want.

[robselina]

in case you do decide to regear, here are the carrier breaks:

D44 3.73 & down / 3.92 & up

M20 2.73 & down / 3.07 & up

[GirlsLoveDirt]

good info

[CowKiller]

awww, comon. lol i runnin 33's on 2.73 gears. lol it moves just fine. even can spin em off the line. lol

[River Beast]

Originally posted by Cow Killer:
awww, comon. lol i runnin 33's on 2.73 gears. lol it moves just fine. even can spin em off the line. lolYou gotta be joking unless you got a 500 CID caddy!!!
:D
I thought my 3.54's on 33's was a dog off the line..

When I went from the above setup to my 38's and 4.89's, my MPG actually improved alot... went from 6-7 to 10-12.. no joke....

[Stuka]

Originally posted by Cow Killer:
awww, comon. lol i runnin 33's on 2.73 gears. lol it moves just fine. even can spin em off the line. lolTake it out of low range there buddy :D

[MIDLERTH]

Actually ive got 33's and 2.73 and i can spin em all the way thru first gear and chirp em in second(400+h.p. 350) I am just interested in gearing down for the trail.

[FSJ Thing]

Yup. I recommend 4.11s for best all around. If you got a 400bhp engine though, I think I'd start shopping for bigger axles cuase it's only a matter of time before you need em, especially if you like to burn the rubber all through 1st gear alot. I would say to replace the carriers with a locker, but with as many pony's as you're running, I say change the gears, get some used carriers, and save locker money for the new axles. Good luck and let us know how it works out!

[River Beast]

I agree with Wagothing.... you're gonna need bigger axles soon with that many ponies under the hood.... tires aint cheap either...

[MIDLERTH]

Well I dont really use the power unless I have to. I dont even burn out ever, I have done it just to see what i got after mods. You guys think if I put a bigger carrier in, weld my amc20, and gear down to 4.11 or 4.56 with a locker i will have any axle problems. I like to use my power to pull trailers and four wheelin. I dont see the need to abuse it on the street. Isnt that where i would damage my axles the most?

[Georgia Mike]

Originally posted by rselina:

M20 2.73 & downAre there even any higher gears than 2.73's :D ?

[netbear]

I think there were some AMC 20 gears in the 2.50
range but they are rare. Might not be my first
choice for a FSJ unless I was running at least
a 38" tire. ;^)

I think 4.11s will work best for you, maybe put
a Detroit locker in the rear if you want extra
traction. A nice limited slip would cost less
if you are on a tight budget. Some of the
aftermarket limited slips work OK for mild off
road use and are easy on the axles. I would not
weld up an AMC 20 diff as it would put too much
strain on 29 sline axles with all that weight.

[Stuka]

I think some AMC20's used in eagles came with higher gears then 2.73's. As they had smaller tires, so they needed to keep the rpm's the same as with larger tires.

[SAustinwag]

just installed 35" MTR's with 4.1 gears along with Posi-. Everything fit just fine in my 83 wag. My AmC 20 had 2.7's before and everything went smooth

[dnixon]

Originally posted by SAustinwag:
just installed 35" MTR's with 4.1 gears along with Posi-. Everything fit just fine in my 83 wag. My AmC 20 had 2.7's before and everything went smoothWe are twins! I just haven't put my gears in yet...

[MIDLERTH]

What was the cost? Did you do the labor or someone else?

[timmirvin]

And what are your RPM/MPH #s??????
Meaning.....what rpm @65mph??????

[MIDLERTH]

SORRY NO TACH. YET! BUT I HAVE O.D. O AT 65 I AM BARELY EVEN PUSHING THE PEDAL. SOUND TO ME TO ABOUT 2200-2700RPM

[Stuka]

Originally posted by MIDLERTH:
SORRY NO TACH. YET! BUT I HAVE O.D. O AT 65 I AM BARELY EVEN PUSHING THE PEDAL. SOUND TO ME TO ABOUT 2200-2700RPMYou have over drive?

[MIDLERTH]

yeah ive got a chevy350 with a 700r4. So far i realy like the r4 been in about 1-1/2yrs now.Had a few 727's ran good but ot enough for a built up 350. last one the case cracked right in half.