My 420SE 126 Merc has developed a rumbling noise (sounds as if a flat tire rrrrrrrr) above 45-50 MPH in the rear end after installing new rotors and tires. Inspected up on a lift with tire rims on and off you can still feel vibration. Differential oil level OK; no metal shavings; half-shafts do not appear to have play; rumbling can still be felt up on a lift; nothing loose; flex discs intact no cracks, center support carrier appears intact no play on main shaft or noise felt there. Is it rear bearings going bad? differential half-shafts needing rebuild? Auto transmission under warranty rebuild about 3,000 miles ago. New tires are Khumos with about 200 miles on them do not appear to have bubble blisters or out of round?

i was thinking bearings or cv kit needed

first try moving the tires and wheels to the front to see if it is in the tire/ wheel combo or the drivetrain.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Did, you change these rotors yourself? If not here is a common problem that people who don't know the W126 do and that is they loosen the big bolt in the middle of the hub at the rear thinking that it has to do with the breaks... It doesn't, it holds the axle to the wheel assembly, the mechanic then bangs the rotors off causing seperation between the axle and the hub. You can see the gap when the CV boot becomes gapped from the hub. I made this mistake and had to bang that sucker back on and retighten the whole get-up. Did you or the mechanic remove all rust from the hub? I could be wrong, but check this possibility or you could get killed... The only reason I ever touched that bolt is because a mechanic said to... Big mistake. were the bearings re-greased ? Sometimes too much grease creates false tension when retightening spindle bolts thus under-tightened and bearing failure and what not.. Just thinking out loud.