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Discussion Starter #1
I have a 2002 Suburban with a limited slip differential. It has 127,000 miles. I'm starting to hear some differential noise under drive conditions. I don't hear any noise in coast or float conditions. I currently have Mobil 75W90 Synthetic lubricant in the rear end. Can I go to Mobile 75W-140 synthetic lubricant without affecting the limited slip mechanism?

I have never towed with this vehicle, but don't know what the PO might have done. It has a trailer towing package, but did not come with a trailer hitch.

I have changed the lubricant viscosity on a number of cars with pretty good success, but none of them had a limited-slip differential.

Any thoughts?

Thanks
 

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I'd stay with the 75/90 and try to track down the noise. Have you tried jacking up the rear on jackstands and have someone listen for the noise?
 

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There is an additive for LSD diffs that you should be running.I have heard that using synthetics with an LSD and no additive can cause damage.I had a tundra that required 90w oil and had to put the additive in with a synthetic but I cannot remember the exact reason why.
 

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No additive required with M1. You could try running the 75-140 and see if the noise stops. The heavier lube will only hurt economy. The front pinion bearing is probably going out. Not uncommon with a 10 bolt that has been running low on Dino.
 

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Discussion Starter #5
Here is what I have done so far:

1. The lubricant has not been run low. The lubricant level was right on the full mark before I recently drained the differential.
2. Synthetic lubricant is what the owner's manual specified. No mention of additive
3. I added GM 1052358 when I recently changed the lubricant.
4. I have had the vehicle up on jack stands and listened to all the bearings (pinion, differential side and wheel) with a mechanic's stethoscope - no unusual noises.

I'm beginning to believe that the problem is the ring gear and pinion since this noise mainly appears under thrust conditions and not float or coast conditions.
 
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