AMC 20 open dif or posi - JeepForum.com
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post #1 of 17 Old 11-17-2008, 07:57 PM Thread Starter
mudnut
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AMC 20 open dif or posi

I apologize if this has been asked a ton of times before. I searched around but with so many keywords (diff, carrier, rear end etc...) I wasn't sure what it would be under.

I have an 85 CJ7 with the AMC20 rear, is there a way to tell if I have an open carrier or a limited slip without pulling the rear cover off? I've got the engine apart now so driving it to find out won't work right now. I haven't owned it for very long and only drove it a couple of times before I pulled the head off so not enough wheel time to have found out that way. Not sure if there would be a vehicle data tag somewhere that I'm not seeing...

I'm trying to decide on a locker and am either looking at an Aussie or a Lock Right. Neither will go in a posi. Had considered the No Slip from Power Trax which does come in a posi carrier friendly model but I can't use a 1 piece axle conversion with it.

I don't want to get into too much money with this as I'm not sure that I will keep the AMC 20 but I'll have it for awhile and want to stick a locker in while I have it. I do want to avoid having to go to the shop to have an open carrier installed just to get the "easy to install" locker in, that just seems like it would be expensive but at the same time I don't want the 2 piece rear axle as I see that breaking at least once before I put in a 1 piece. I've never "set up" a rear end before and not sure that I'm even set up for it. (Damned if I do and Damned if I don't it would seem)

I don't plan on doing any hard core wheeling but going out with the local club on easy to moderate trails I can't see being that comfortable without a locker (cheaper than a winch LOL)

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post #2 of 17 Old 11-17-2008, 09:40 PM
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Quote:
Originally Posted by mudnut View Post
I apologize if this has been asked a ton of times before. I searched around but with so many keywords (diff, carrier, rear end etc...) I wasn't sure what it would be under.

I have an 85 CJ7 with the AMC20 rear, is there a way to tell if I have an open carrier or a limited slip without pulling the rear cover off? I've got the engine apart now so driving it to find out won't work right now. I haven't owned it for very long and only drove it a couple of times before I pulled the head off so not enough wheel time to have found out that way. Not sure if there would be a vehicle data tag somewhere that I'm not seeing...

I'm trying to decide on a locker and am either looking at an Aussie or a Lock Right. Neither will go in a posi. Had considered the No Slip from Power Trax which does come in a posi carrier friendly model but I can't use a 1 piece axle conversion with it.

I don't want to get into too much money with this as I'm not sure that I will keep the AMC 20 but I'll have it for awhile and want to stick a locker in while I have it. I do want to avoid having to go to the shop to have an open carrier installed just to get the "easy to install" locker in, that just seems like it would be expensive but at the same time I don't want the 2 piece rear axle as I see that breaking at least once before I put in a 1 piece. I've never "set up" a rear end before and not sure that I'm even set up for it. (Damned if I do and Damned if I don't it would seem)

I don't plan on doing any hard core wheeling but going out with the local club on easy to moderate trails I can't see being that comfortable without a locker (cheaper than a winch LOL)
Jack up the rear end and turn one of the wheels, if the other side turns in the same direction its a posi. If it turns the opposite way its open. Just so you know, AMC 20 rears were rare w/posi set ups, and I would advise against installing one. You can get a Dana 30 or 35 used with a taller gear set than you probably have for $ 150.00 to $ 200.00 for either front or rear.
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post #3 of 17 Old 11-17-2008, 11:39 PM
Max-Bilt
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one piece axle kit and a spool would set you up just fine, might chirp around the corners a little bit but your not building a speed racer, they handle on the road just fine, and you would be upgrading the axles as well and you would have under 500 bucks into it. As for finding out what carrier you have, just pull the pan when was the last time you or anyone changed the diff fluid?...... exactly! just my .02 good luck
PS email me if you want some tips on setting up a rearend if you decide to go this route, or else give me a shout on my cell

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post #4 of 17 Old 11-18-2008, 05:21 AM
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I have seen Trac loks so beat out that they were essentially an open carrier.You will need to drop the cover to confirm what you have.
Steer clear of spools unless your building a trail specific rig. They don't handle well on dry pavement and seriously suck on ice and packed snow.
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post #5 of 17 Old 11-18-2008, 08:52 AM
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Quote:
Originally Posted by jeepdaddy2000 View Post
I have seen Trac loks so beat out that they were essentially an open carrier...
I've never seen one any different either.

this link can help you with your diff, assuming it's stock

http://www.jeeptech.com/axle/amc20.html

a little scraping, and you should be able to find it.

Hoss

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post #6 of 17 Old 11-18-2008, 10:42 AM
southshore30
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There is usually a sticker inside the glove box on the jeeps factory equipped with the L/S warning you the vehicle is equipped with a limited slip differential so be careful driving on wet or slippery surfaces. It may have been torn off years ago or never had one either. Mine has the sticker. Jack up the rear and rotate the tires and as stated above, if they rotate the same direction you have a factory, or aftermarket limited slip carrier.
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post #7 of 17 Old 11-18-2008, 11:30 AM
80cj
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Quote:
Originally Posted by Jeffdmaintman View Post
Just so you know, AMC 20 rears were rare w/posi set ups, and I would advise against installing one. You can get a Dana 30 or 35 used with a taller gear set than you probably have for $ 150.00 to $ 200.00 for either front or rear.
Actually, the Trac Lok limited slip option was very common in CJ's with AMC 20 rears. Dana 30 for the front, yes. Dana 35 in a CJ not a good idea. An AMC 20 with 1 piece shafts is heavy duty compared to a Dana 35.

Last edited by 80cj; 11-18-2008 at 11:51 AM.
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post #8 of 17 Old 11-18-2008, 12:59 PM Thread Starter
mudnut
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Outstanding, thanks for the info guys... looks like I'll break out the floor jack in a couple of days and crank up the rear end and I'll hit that link about the AMC20 info.

I wasn't thinking of a 35 for the rear though. I would like to find an old Scout and pull the 44s out for a swap but I live in PA and they are really picky about the no tread sticking out past the fender thing. Especially here with a state training barracks a few miles away. The local cops would pretty much hold to bag while you robbed the bank but not the state boys... So for now the 20 with a locker and 1 piece will be the ticket (no pun intended)

With a little luck I'll find that this has an open carrier, stick in an Aussie or Lock Right, a 1 piece axle and be done. And Max I totally get where you're coming from with changing the dif fluid, that's next on the list after I get the head back on and buttoned down. And I'll shoot you a call if I need to set up the axle with an open carrier...
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post #9 of 17 Old 07-16-2009, 06:31 PM
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I am trying to figure out if I have a dana 44 or amc 20 rear end and if it is open or posi (86 cj7). I jacked it up and turn the tires and one spins the opposite way of the other. However if I spin out on loose ground or grass BOTH tires will spin. I didn't think an open rearend would do that. I thought only one wheel would spin.

How do I tell if I have the amc20 or danna 44 I can't find the stamp and there is no tag.
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post #10 of 17 Old 07-16-2009, 07:48 PM
kickingprop
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diff cover...

AMC 20 diff cover is round
D44 is an asymmetric hexagon (slightly offset)

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Phase One : 5.3L Vortec/4L60E, Moser axles for AMC20, Twin Stick'd Dana300 - Completed
Phase Two: Bedliner, Rollcage, Seats, BESRK Rear Bumper w/ tire swing, Soft Top, and a few other goodies - Mostly Complete
Phase Three: Waggy 44 front, Scout D44 Rear, 4.56's, ARB's (F/R) SOA with YJ Springs, 35x12.50x15 BFG MT - Not Even Close to beginning

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post #11 of 17 Old 07-17-2009, 08:25 AM
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Quote:
Originally Posted by 80cj View Post
Actually, the Trac Lok limited slip option was very common in CJ's with AMC 20 rears. Dana 30 for the front, yes. Dana 35 in a CJ not a good idea. An AMC 20 with 1 piece shafts is heavy duty compared to a Dana 35.
also- wouldn't the 35 have 5x4.5 bolt pattern?

Hoss

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post #12 of 17 Old 07-17-2009, 08:44 AM
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Originally Posted by Stacydmcc View Post
However if I spin out on loose ground or grass BOTH tires will spin. I didn't think an open rearend would do that. I thought only one wheel would spin.
If the traction is about equal on both tires they will both spin with and open diff. You see one spin when there is a sizable difference in traction.
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post #13 of 17 Old 07-20-2009, 07:53 PM
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I see. Thank you. That explains it.

"I'm trying to decide on a locker and am either looking at an Aussie or a Lock Right. Neither will go in a posi."

Is this true? My front is a posi. it seems. When I lock the hubs and spin the wheel both turn the same direction. I wanted to put a assie locker in both front and rear. can I not?

I'm sorry...I'm not trying to hijack the thread. This just confused me when I read it.
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post #14 of 17 Old 07-21-2009, 01:31 AM
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Quote:
Originally Posted by Stacydmcc View Post
I see. Thank you. That explains it.

"I'm trying to decide on a locker and am either looking at an Aussie or a Lock Right. Neither will go in a posi."

Is this true? My front is a posi. it seems. When I lock the hubs and spin the wheel both turn the same direction. I wanted to put a assie locker in both front and rear. can I not?

I'm sorry...I'm not trying to hijack the thread. This just confused me when I read it.
Stacy, if you have a posi (limited slip differential) in a diff, then you cannot just add a lunchbox locker like an Aussie or a LockRight. Those lockers are designed to be installed in a differential that has an open carrier, and the OEM carrier is retained during the installation.

If you're going to replace the posi with a full locker, either an auto locker like a Detroit Locker or a selectable locker like an ARB Locker, then that's certainly do-able, since you'd be removing the entire posi carrier and guts and replacing it with the full locker.

1977 CJ7, AMC360 V8 w/ headers, DUI HEI, Edelbrock intake, Holley 4150 carb, , TF999, D300, D30 front and AMC20 rear with 4.56 gears and lockers both ends, 4" susp lift, 2.5" body lift, 35" BFGs, ARG steering, 8000-lb winch, etc.
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post #15 of 17 Old 07-21-2009, 08:22 PM
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Thank you for the clarification. I appreciate it. Gives me something to think about I guess.
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