new shocks but knocking noise in rear at low speeds

What is your question?

Recently had new shocks and a lot of other work done but the car knocks or thumps in the rear at low speeds. The sound vanishes on high speed roads. What causes it? We checked on the spare and the jack and neither are the cause. The car drives very well and there are no other issues. I want to sell it but I need to know what could cause a knock in the rear of the car.

What makes this problem better or worse?

Driving at a higher rate of speed makes the noise cease. Driving at low speed on suburban roads causes the knock or thump.

How long has your 2007 Cadillac DTS had this problem?

A couple of months after work was done to replace the shocks.