1995 Buick Roadmaster. Low speed metallic noise

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Hello all I have been hearing a sporadic groaning/clunking sound from my rear axle. It is a limited slip rear end(GM posi). The noise in question is only noticeable at parking lot speeds with the driver's window open while making a turn. I don't think it's the bearings as I don't hear typical worn bearing noise/clicking but taking the axle apart to check them is something out of my comfort zone. It doesn't appear the axle is shifted or bent either and a quick check on the rear brakes don't point out anything rubbing or binding. The rear control arm bushings are also intact. Whatever this noise is, it doesn't affect the way the car steers or tracks. The noise is more aggravating than anything. If anyone with extensive knowledge of GM B body cars can chime in, that would be great.
 
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Change the rear end gear oil with just about any FULL Synthetic. Most will have the friction modifier in it for the posi clutch packs. Check your manual for the correct viscosity 75W90/75W140. Should fix the problem.
 
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You are hearing the clutches in the limited slip rear differential. Pick up a bottle of ACDelco Limited Slip Lubricant Additive, part number 88900330 - and your favorite gear lubricant. Service the rear differential with the new gear lube & additive, and make some figure 8's in a parking lot afterwards to work it into the clutches.
 
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If this is a G80 rear end, LSD additive isn't required. A fluid change is certainly worth starting with.
 
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I think GM passenger cars got limited-slip diffs, with clutches that require additive (separate or blended into the fluid). Trucks get the gov-lock diff that doesn't require extra LS additive. A fluid change would be a good idea if you're up to it. As a shortcut, you could get a tube of additive and put it in by increments, doing figure-eights in between to see if the noise goes away. If that fixes it, you know the fluid was worn out and can change from there.
 
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Originally Posted By: Rhymingmechanic
I think GM passenger cars got limited-slip diffs, with clutches that require additive (separate or blended into the fluid). Trucks get the gov-lock diff that doesn't require extra LS additive. A fluid change would be a good idea if you're up to it. As a shortcut, you could get a tube of additive and put it in by increments, doing figure-eights in between to see if the noise goes away. If that fixes it, you know the fluid was worn out and can change from there.
+1 This
 
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Interesting to see this. Granted I haven't dug too much into it, but when I'm on eBay looking at G80's for my truck, I see the Impala and Camaro listed in the fitment. I guess this is eBay.. LOL.
 
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Originally Posted By: dlundblad
If this is a G80 rear end, LSD additive isn't required. A fluid change is certainly worth starting with.
It is. The tag on my Roadmaster LSD says it is required.
 
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