126 Rear Rumbling Noise

[Carlo(s)]

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?