560SL::humming and grinding noise from rear
 

Just took delivery of an '87 560SL and i notice a humming and grinding noise coming from the rear end. It happens at very low speed, say 20 MPH, where it sounds like a grinding, and then as I accelerate, the humming gets higher pitched.

would love to hear any thoughts

thanks in advance

check flex disc, if ok get both back wheels off ground and rotate , may be parking brake hanging up , or caliper sticking, less likely and more severe, rear diff , or rear bearings