Trivia info only.
Put my co-worker onto a 1995 C4 from friend of mind. Car is prestine.
After driving from Portland, Oregon to Clarkson Wa. He noticed the rear end would make a little noise when turning right or left. The previous owner had just put Red Line synthetic in the differential plus additive. The new owner drained and replaced with GM spec oil. plus additive. Made six figure eights and noise went away and has not returned

 

Any thoughts? Anybody experience the same?

 

Interesting. I changed my diff fluid this past spring and used the Red Line gear oil (I think it's synthetic...) and was told by several reputable sources that it INCLUDES the additive, so not to add any to it. Maybe that was the problem?

 

He should have made six figure eights before the change....hard to tell.

 

Maybe the donuts, fixed it. I have synthetic in diff(+ 2 bottles of addi), trans, OD, power steering and motor. No noises, no leaks, no problems.