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Limited slip differential noise

My Chevy 96 Impala SS makes a loud noise that comes from the limited slip differential. The noise started after I changed the oil in the rear end. I have used Lucas 80W-90 oils and about 5oz of an additive for limited slip differential. After driving the car for 10 miles the differential started to make noise. I thought, perhaps I should not use the additive with the Lucas gear oils or perhaps I added too much of it. I have removed about 1 quart of the oil and replaced it with 1 quart of plain oil, the noise did not go away. Next I have opened the differential and remove all oil and filed it with plain 80W90 oil no additive for limited slip was added. The noise is still there, it is especially loud at very low speed while making turns (speed as slow as very slow walk). Before I change the oil everything was OK.

Any suggestions what to do next?

The additive is absolutely necessary for your LSD. Get the recommended gear oil and additive (I suggest the real OEM GM stuff for both but for sure the additive) and add the recommended amount of the additive. You’re damaging the clutches if they’re groaning on turns.

Did you fill it on level ground until the fluid came back out the fill plug? Did you check it later to make sure there were no air bubbles giving you a false reading after filling?(plug out, fluid right at base of hole? Use finger tip if can’t see it).

What does the additive for limited slip differential do?
What is the difference when you do not have it added to the oil or have too much of it in the oil?

It’s a friction modifier that allows the clutches and plates to glide smoothly over each other versus chattering which is what’s happening now. It’s only like $10 at the dealership so for a couple of bucks difference, it’s not worth the trouble. A lot of people run into this issue using the cheap or generic stuff. Get the GM additive at the dealership…

I will try the GM product and let you know if it works.
Thanks

Yep, definately get the GM rear end lube and the posi trac whale oil additive. I had a new Olds and got the disc chirp within 2000 miles. Used the whale oil additive that that quieted it right down.

First, find out FOR SURE what the factory required lubricant is AND THEN USE IT!!! If a limited-slip additive is needed, use the GM product!

Thanks,
I used the GM additive for limited slip differential from the dealership and now everything is perfect. Is the additive actually made of whale oil, as Bing suggested?

http://www.littleredservices.com/FieldDocs/MSDS/Limited%20Slip%20Axle%20Lubricant.pdf

It should have a “no whales were harmed or killed when they were milked for their oil” symbol on the bottle (it is a picture of a scuba diver with a pail and a stool), if not, they killed the entire pod, babies included, to get that little bottle of oil.