Rear End "Graunch"

I have a 1992 XS V6 Auto. Trooper. It has suffered from that unexplained "graunch, transmission slip", from a dead start since I bought it (used).
After reading a few posts here about the possible cause being degraded rear differential fluid, I asked my mechanic last week to replace the diff oil with the best available. He did, and the problem has disappeared!
He used an American oil , so it wasn't familiar( I'm DownUnder). I think it was MUTROL, or MUROL, something similiar. I'm sure you guys stateswide will recognize it.
If you have this problem, can't hurt to give it a try.
Johnno
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Johnno, was this slip an everyday occurance or a once in a blue moon...i think mine has an occasional slip when first starting sometime but i can't really tell it so small...
mike

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Mike,
No it wasn't there all the time. Seemed to be more apparent if I was on a slight incline before starting off. At times you would swear the rear tires were losing traction! It was never there from a cold start, but would come in at times after say 30 mins. suburban stop/start motoring (the diff. oil was hot?). Who knows. All I know is the damn thing has gone away after the diff. oil change!
Johnno
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JayEye wrote:

This has me baffled. Isn't the differential gear to gear?
Frank
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No mystery here. The rear diff is of a limited slip type which requires friction modified oil. If this is not used then, especially when the oil is hot, when the differential works as in turning a corner then the friction plates slip with a graunchy noise. Another common word for the noise is a 'squawk. The oil to use in a LS diff is LS oil. Any LS90 or 90LS EP oil will have the same soothing effect. Brand is not important because gear oil is a commodity product which is all made to the same standard, which in this case is GL4 or GL5 gear oil for Limited Slip differentials.
Huw
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I knew there was an answer somewhere, but not being mechanically minded I couldn't reason it. You've now given the post a logical reason for the possible slippage, and fix. Thanks.
Johnno
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Johnno, THANKS, you don't know how happy the wife is going to be. She has mentioned on occasion as with all wifes and cars they fear the doom sometimes. your second post sounds practically identical to our little situation. I give it a try. If u can tell me what did it cost you and who did it????
Thanks mike

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Hi Mike,
Have just dug out the invoice. The oil used was MOTUL 90. Looks like it took close to 2 litres (4 pints,? a quart?) sorry we're decimalised down under.
The mech. also used MOTUL for the engine oil change, obviously not 90 grade, but no detail on that. The diff. oil cost me A$23. (about US$14) plus labour (say US$30. per hour) so all up, no more than US$30 total.
My mech. builds, prepares, and races saloon cars, and says he wont use any other oil/lubricant than the MOTUL range, even though it's hard to get hold of here in Oz.
I wouldn't think it's a big job to do yourself. Depends of course whether you like getting your hands dirty!
Johnno
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THANKS, i didn't notice the down under part till wife told me.

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