W124 Rear Suspension "Thump Thump Thump"

[Dinoman]

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.