Was hoping to find some info about my Benz I got recently..bought 94 s320..drove for a while n now rear end makes a grinding noise n locks the wheels up..had it on jack stands n doesn't lock up?? Think its ring n pinion?? N e 1 out there have a decent plan of attack to fix it..car has 181,000 n still runs fantastic..please help..n e I do would b much appreciated