ok im trying to help a friend who has a 1993 camaro z28 lt1 when ever we have people in the backseats and we pass a set of rail road tracks the rear drops you feel and here a loud thump the rear and it has happen when ther no one in the back seats it just not as common well we first thought it was a the shocks so we replaced them but we get the same thump over agian please help i have noticed the sound came from the passenger rear i checked the suspention and both bump stops have rotten off

 

Get the bump stops..... FYI: They are yellow now, not black.... Most dealerships keep them in stock..

 

Also check the exhaust hanger bushing , they're probably shot. So the overaxle exhaust pipe it's likely hitting the axle tube, and the panhard support bar.

 

Here you go:
https://www.camaroz28.com/forums/sho...ght=bump+stops