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Unread 12-14-2004, 05:55 PM   #1
nickdz
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Join Date: Jun 2004
Location: Northern Virginia
Posts: 45
AMC Trac-Loc vs. Open Identification Help

I am trying to determine whether my AMC 20 rear diff. is open or limited slip (trac-loc). I am ordering a powertrax no slip system and want to make sure I order the correct part.

The axle has an "N" stamped into the casing and according to jeeptech’s website, that indicates an open diff with 3.54 gears.

Can anybody confirm jeeptech’s identification chart? Even better…can anyone point me in the direction of a similar but separate chart?

The reason for my wanting to double check jeeptech’s chart is I have crudely calculated my gearing ratio and have come up with 3.73. That’s not to say both aren’t correct, but I would feel a lot better if I had confirmation as to whether this is an open or trac-loc diff before I order a powertrax no slip traction system.

Worst case scenario…I break her open to see for myself and leave her out of commission for a week or so while the parts come in.

Oh yea, the jeeptech chart I am referring to can be found at:
jeeptech AMC 20 differential identification

__________________
1980 CJ7
- 151 "Iron Duke"/SR4 converted to Chevy 350/SM465
- Moser One-Piece Rear Axles
- Locked All Around
- Mastercraft Seats
- Durabak Interior and Exterior
- KargoMaster Cage
- Way too many minor repairs/upgrades to list (emphasis on "repairs")
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Unread 12-14-2004, 07:50 PM   #2
wm69
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Join Date: Jun 2003
Posts: 3,162
what year jeep is it? if it's a widetrac (82 and up) it could be an "H" that looks like an "N" (those codes are hard to read with 20 years of crud back there.......)

Narrow Track AMC 20
: Code Gear Ratio Diff Type
: AA 2.73 Open
: DD 2.73 Trac-Lok
: BB 3.31 Open
: CC 3.31 Trac-Lok
: A 3.54 Open
: N 3.54 Trac-Lok
: GG 3.73 Open
: Q 3.73 Trac-Lok
: L 4.10 Open
: M 4.10 Trac-Lok

: Wide Track AMC 20
: Code Gear Ratio Diff Type
: D 2.73 Open
: DD 2.73 Trac-Lok
: B 3.31 Open
: BB 3.31 Trac-Lok
: A 3.54 Open
: AA 3.54 Trac-Lok
: H 3.73 Open
: HH 3.73 Trac-Lok
: C 4.10 Open
: CC 4.10 Trac-Lok

Jack the rear end up and spin one wheel. If the other one goes forwards too it's a traclok, if it goes backwards it's an open diff.
__________________
85 CJ7 258, borla header, Team Rush, MC2100 ,optima batt, Warn 8274, agr super box 2 & pump, T5 w/ B&M shifter, centerforce 2, superior 1 piece axles, warn hubs 2.5 in lift, 31" BFG MT

85 CJ7 258, A/C, T176, MC2100, Team Rush, Warn XD8000i, superwinch hubs, 3in lift 31" BFG AT/KO
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Unread 12-15-2004, 03:02 AM   #3
nickdz
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Join Date: Jun 2004
Location: Northern Virginia
Posts: 45
"Jack the rear end up and spin one wheel. If the other one goes forwards too it's a traclok, if it goes backwards it's an open diff."

Good call....
__________________
1980 CJ7
- 151 "Iron Duke"/SR4 converted to Chevy 350/SM465
- Moser One-Piece Rear Axles
- Locked All Around
- Mastercraft Seats
- Durabak Interior and Exterior
- KargoMaster Cage
- Way too many minor repairs/upgrades to list (emphasis on "repairs")
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Unread 12-15-2004, 07:23 AM   #4
lockedandlowded
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Join Date: Mar 2004
Posts: 45
It could have a limited slip CARRIER and the clutches could just be out!?! Then thjey would spin opposite.
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Unread 12-15-2004, 08:01 AM   #5
knifeboy2
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Join Date: Mar 2003
Location: Macomb, IL
Posts: 485
Spinning the wheels can be correct but as stated if its worn out they'll spin opposite. Really the only good way to know for sure is to open it up. Its really not that hard and you'll need to do it anyways. If the carrier is tapered its an open diff, but if the carrier is boxy then its LS. While you're in there count the gears on the ring and on the pinion and you'll have your gear ratio. Good luck.
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"If stupidity got us into this mess, why can't it get us out?" -Will Rogers
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Unread 05-22-2010, 12:28 PM   #6
rkinks35
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1985 CJ7 
 
Join Date: Jul 2009
Location: Newtown, CT
Posts: 37
I think im currently having the same "worn out" problem. I have a AMC 20 rear axle with BB engraved on the shaft, I also counted the gears and it does match the BB 3.31 Trac-Lok. Cant see inside the carrier to get a glimpse of spyder gears. Theres a lot of slack and very easy to turn both wheels in opposite directions. Any ideas? Whats wrong and what needs to be fixed.

I also blew a drive shaft and keep randomly hearing a correction from the rear. Thats why I am trouble shooting my AMC 20, I purchased and installed this recently, dont remember if it was used cause CJ was sitting for so many years. But I have a V8 304 engine that tore the crap out the gears before this axle replacement
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