W124 Rear Suspension "Thump Thump Thump"
 

I have a 300D W124 1993 with a very slow speed thump-thump-thump in the rear. I rotated the tires, and the Thump-thump-thump is still in the rear. It happens from zero to 5mph and then will smooth out. I've brought it to a garage and they think it's the rear knuckle/spindle just from the wheel when on a lift being able to 'wiggle' when rocked from the 12 and 6 o'clock position. The spindle/knuckle is expensive and difficult to find. I"m wondering if it might be the 5 point arms with rubber mounts that attach to the spindle. Is there any test to find out easily? Thank you.

get a 2nd opinion. a rotational noise is not normally in the suspension but the wheel, tire, axle and/or bearing.

sounds like a broken shock mount. My kid's BWM did same thing from the back end.

the low speed thump thump noise without road roughness on a W124/W201/W210/W140 is usually the driveshaft support bearing and its rubber hanger.

quite easy to diagnose too.

Anyway - if the rear spindle is moving - its usually the toe link or the camber link bushings - need to replace entire arms. Make sure the whole spindle is moving and not just the hub and wheel which means a bad wheel bearing (not too bad on a sedan with an in situ kit (front wheel drive bearing cup set) you can rent from autozone now.