Posi rear groaning and shuttering a little
#1
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Posi rear groaning and shuttering a little
After driving my 99 with a posi rear for a while when I pull into a parking lot or just generally turn sharp it kind of groans and shudders slightly. It is definitely coming from the back of the vehicle, and it stops the second I go straight again. This tells me it is in the rear differential. I don't know much about posi's other than I think they have clutches in them that slip, making it LIKE a differential, just....tighter. I will tear into it, check that everything is tight and has the right backlash and everything, and change the fluid. Any other heads up I should be looking for while I'm in there? Don't know much about posi's, but I have done transmisions and setup ring and pinions and stuff like that. Thanks.
#2
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Mopar has an additive for the limited slips. Might be all you need. When's the last time you changed the fluid and did you use the right stuff?
#3
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Just bought this vehicle, today was the first drive into work with it. So, no idea what is in it. If nothing else I was going to change the fluid with the right stuff, and while I was in there, just look around. Actually, I noticed today that it seems to do it more when turning partway, not all the way sharp. A few people that I have talked to today say that is normal for a posi rear car, especially a relatively short wheelbase car, and others say no way that is normal. Seems like a short wheelbase car would have a bigger differance in inside wheel speed versus outside wheel speed. Plus Jeeps turn in pretty sharp compared to a long pickup truck which is more common to have a posi. I am babbling now..............
#4
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What do you mean by POSI. The stock LSD, which sounds to be working, but in need of oil and additive. OR are we discussing an aftermarket unit?
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"Posi" or "Posi-Traction" is a Chevy brand name for their version of a clutch type limited slip diff. I believe Trac-Loc is the Chrysler/Jeep name.....either way, they are both limited slip diffs. I'd start with a clean out and gear oil change. If it still makes a noise, and u are positive it is a factory LSD, then poll the plug and add the small tube of friction modifier. If the LSD doesn't chatter in a turn, it doesn't need the modifier additive as the additive just makes it slip more/easier which means slightly less torque to both wheels (in a turn).
#6
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Change the gear oil (75w-90) with a friction modifier and you should be good. Mine did that when I first got it too, changing it made an immediate difference no more noises.
#7
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Well, the guy I bought it from said it was a factory "posi", I guess that means it is an LSD as was said, they are basically the same thing. When I turn corners on dirt roads the inside tire spins a little, so I am sure it's not just a standard open diff.
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#9
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Year: 1998
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Spinning 1 tire in dirt sounds like an open diff or possibly a worn out clutch type lsd. Even a worn out lsd will spin both wheels the same direction when the axle (both wheels) is raised. Open diff, wheels spin opposite direction.
#10
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When I say "spin the inside tire" I don't mean step on the gas and just the inside tire spins, I mean just idling around the corner the inside tire just turns over a little bit. When I hit the gas, both tires spin.
#11
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Year: 1998
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My Auburn LSD was making the same noises. It has about 4000 on it. I changed the break in oil at 500, and it started making noises about 3500. I put 80-90w with 6oz additive in, just like the book said. Took it over to OK4wd, and opened it back up. Everything looked good, so we put in Amsoil 75-140w, and 8oz. of additive. Nice and quiet now, and still works the way it should. I don't crawl over really tough stuff, because it is my daily driver. If I did I would have bought a real locker.
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Finally got it apart. Kind of looks like a regular open differential to me. That's bad news. Other opinions? Looks like just regular spider gears to me.
Last edited by superdrag; 10-23-2011 at 10:02 AM.
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Originally Posted by superdrag
Finally got it apart. Kind of looks like a regular open differential to me. That's bad news. Other opinions? Looks like just regular spider gears to me.
Its a trac lock