[FirstOwner69]

I agree that you need to drain and fill with new lube and friction modifier. To make it easy, there are 2 differential gear lubes I've used in the last year that come with the friction modifier already added. I used ACDelco Dexron 75W-90 LS Gear Oil in my 1999 Vette and Mobil 1 Synthetic Gear Lube LS 75W-90 in my 2001 Jeep Wrangler. Both solved the problems. It should be noted that Mobil 1 is not recommended for Vettes.