Rear diff question

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HandofGod
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Joined: Fri Jan 03, 2020 8:33 am

Rear diff question

Post by HandofGod » Mon May 11, 2020 4:08 pm

So I’m putting new diff covers on the Wag and it looks like someone put some kind of LSD in there - it has an LSD lube tag, and the wheels spin the same way. Is there any way to identify it without taking the gears apart? Here’s some pics.
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Last edited by HandofGod on Mon May 11, 2020 7:01 pm, edited 1 time in total.
White ‘91 GW with 350 swap. 700r4 transmission. NP 241c T-case. Rusty’s 3” body lift. Currently on 31x10.5x15 Milestar Patagonia M/T tires. Holley sniper EFI and complete Novak cooling system.

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REDONE
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Location: Lakewood and Bailey, CO

Re: Rear diff question

Post by REDONE » Mon May 11, 2020 4:21 pm

It appears to be a Spicer trac-lok. They aren't terrible but they aren't great either. It's a constant-bias friction clutch limited slip. It has some spring washers that apply pressure to a clutch pack. Once the difference in resistance between each axle shaft overcomes the static friction if the clutch pack, it allows differential wheel speed. The 2 reasons it's not great is that the static friction torque threshold is almost meaningless compared to the weight of a big old steel truck, and once it wears out (since you can't feel it do anything anyway), it lets the spiders slop around until they jam and shatter.

You're ahead of the curve knowing that you have it! Most of the tracloks I've seen blown up happened when the owner didn't know they had an lsd. I wouldn't swap in a trac-lok, but I wouldn't bother with replacing one if a found it in my axle. Be sure to use an LSD friction modifier in the gear oil and run it until you want something else. :)
79 J-10 (Honcho Mucho) KE0LSU
304/Performance Fuel Injection TBI/MTA1/SP2P/Magnum rockers
T18/D20/D44s&4.10s/33" Mud Claws
Grizzly Locker Rear
4" front spring drop, 5" rear shackle flip
Chevy style HEI (ECM controlled)
Dolphin "Shark" gauges in a fancy homemade oak bezel
3/4 resto, rotting faster than I've been fixing it.


Topic author
HandofGod
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Joined: Fri Jan 03, 2020 8:33 am

Re: Rear diff question

Post by HandofGod » Mon May 11, 2020 6:54 pm

Thanks! I am planning on a real locker for the rear eventually, but I was working under the assumption this was just an open diff. I haven't checked the front yet, but eventually I was thinking either a mechanical (no clutch, all gears) LSD, or another locker up there too. For now though, I'm pleasantly surprised to find this in there.
White ‘91 GW with 350 swap. 700r4 transmission. NP 241c T-case. Rusty’s 3” body lift. Currently on 31x10.5x15 Milestar Patagonia M/T tires. Holley sniper EFI and complete Novak cooling system.

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Stuka
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Re: Rear diff question

Post by Stuka » Mon May 11, 2020 7:13 pm

The clutches may well be worn out, which means it will act like an open diff. But adding friction modifier will help it to work like it should.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


Locked and Loaded
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Re: Rear diff question

Post by Locked and Loaded » Tue May 12, 2020 4:57 am

Just keep in mind a lunch box style locker won't work with a trac loc carrier.
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Stuka
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Re: Rear diff question

Post by Stuka » Tue May 12, 2020 7:19 am

Locked and Loaded wrote:
Tue May 12, 2020 4:57 am
Just keep in mind a lunch box style locker won't work with a trac loc carrier.
Good point. To add a locker, it needs a full carrier replacement. Either an open carrier with a lunch box, or a full carrier locker like a detroit or ARB.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

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REDONE
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Re: Rear diff question

Post by REDONE » Tue May 12, 2020 7:33 am

I doubt any PO would put a trac-lok in the rear and then something better up front(I'm pretty sure it's factory). If he wants a lunchbox rear, he could flippy-flop the front & rear carriers. While you can't lunch box a trac-lok, you can Lincoln a trac-lok, which is really the best thing to do with a trac-lok for both traction and toughness. :-bd
79 J-10 (Honcho Mucho) KE0LSU
304/Performance Fuel Injection TBI/MTA1/SP2P/Magnum rockers
T18/D20/D44s&4.10s/33" Mud Claws
Grizzly Locker Rear
4" front spring drop, 5" rear shackle flip
Chevy style HEI (ECM controlled)
Dolphin "Shark" gauges in a fancy homemade oak bezel
3/4 resto, rotting faster than I've been fixing it.


Topic author
HandofGod
Posts: 29
Joined: Fri Jan 03, 2020 8:33 am

Re: Rear diff question

Post by HandofGod » Tue May 12, 2020 12:07 pm

Yeah I wasn’t going to go lunch box - probably ARB (on board air has additional advantages. I’ve already thought about maybe putting this up front when that happens. Thanks for the help guys.
White ‘91 GW with 350 swap. 700r4 transmission. NP 241c T-case. Rusty’s 3” body lift. Currently on 31x10.5x15 Milestar Patagonia M/T tires. Holley sniper EFI and complete Novak cooling system.


Topic author
HandofGod
Posts: 29
Joined: Fri Jan 03, 2020 8:33 am

Re: Rear diff question

Post by HandofGod » Tue May 12, 2020 6:49 pm

Another question - as you guys can see, the fluid hole, or whatever it’s called, is a good bit higher with the new cover - should I still use the normal amount of lube or add more to get it right up to the hole?
White ‘91 GW with 350 swap. 700r4 transmission. NP 241c T-case. Rusty’s 3” body lift. Currently on 31x10.5x15 Milestar Patagonia M/T tires. Holley sniper EFI and complete Novak cooling system.


rocklaurence
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Re: Rear diff question

Post by rocklaurence » Wed May 13, 2020 5:30 am

I have those SOLID covers on two FSJ--love them. No, dont fill it to the bottom of the new hole--it will be over filled and likely push oil out the vent. I use a piece of wire bent at a 90 to set the fluid level close to the original. Make sure to let the oil roll out to the axle bearings and then final fill.


Topic author
HandofGod
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Joined: Fri Jan 03, 2020 8:33 am

Re: Rear diff question

Post by HandofGod » Wed May 13, 2020 9:22 am

Thanks
White ‘91 GW with 350 swap. 700r4 transmission. NP 241c T-case. Rusty’s 3” body lift. Currently on 31x10.5x15 Milestar Patagonia M/T tires. Holley sniper EFI and complete Novak cooling system.

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dodgerammit
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Re: Rear diff question

Post by dodgerammit » Wed May 13, 2020 7:56 pm

I'll recommend a Truetrac for the front. I had one in my W350 with 44 front. Highly functional on the street with great snow manners.
84 Grand Waggy-Radio Flyer (Garnet Red/3M Ebony Metallic woodgrain, with tan interior) AMC 360/727/229 TFI conversion, MSD streetfire ignition, D44/AMC20 Serehill tailgate and headlight harnesses :fsj:

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Stuka
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Re: Rear diff question

Post by Stuka » Wed May 13, 2020 8:08 pm

Those covers with the higher hole are intended for a front high pinion D44. There is a version with a lower hole. And some covers with two, so they work for high or low pinion.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


kayenhere1
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Re: Rear diff question

Post by kayenhere1 » Thu Aug 13, 2020 8:08 am

rocklaurence wrote:
Wed May 13, 2020 5:30 am
I have those SOLID covers on two FSJ--love them. No, dont fill it to the bottom of the new hole--it will be over filled and likely push oil out the vent. I use a piece of fortnite hoodie wire bent at a 90 to set here the fluid level close to the original. Make sure to let the oil roll out to the axle bearings and then final fill.
thanku for this!

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