1998 blazer LT. I recently got new tires no vibration drove straight. Last week did the rear differential. used to make a metallic grinding sound it was very low on fluid and a possible leak from pinion seal. Added fluid new gasket and rtv sealent. Replaced rear u joint on diff but not the front one due to auto part stores closed and didnt have all things to pop the joint out. after about a week it started shaking again. the rear left rotor is 13/16 and the right is 11/16. cant seem to stop the noises or vibrations at all any help or ideas to try before taking it in is much appreciated. Also i keep getting a emissions control leak small code and a week ago i got a emissions control system failure anybody know how to stop it what to do to fix it at all. Thanks again everyone. have a good weekend

 

Metallic grinding sound from diff is bad......very bad. Check the u-joints, but I think the diff is shot.

 

i know its bad sound it stopped after i added fluid until it came out the drain hole. other than that an occasional clunk when your heavy on the gas its ok. but goin 45 or higher it seems to hum or vibe really bad and it makes cd's skip too.

 

sounds like a bad bearing in the differential...a bad u joint needle bearing will cause a vibration also