I have a 2000 Grand Prix GT and my front passenger brake caliper and rotor are very loose. All the bolts are tight. When I am driving I can hear a thumping sound coming from that side and it gets worse when I let off the gas and slow down without pressing on the brakes. I just got done making sure that the lug nuts on the tire were tight and when I shake the tire, I can see that the caliper moves. So I took the tire off and checked to make sure that the bolts on the caliper were tight which they were. Does anyone have any idea on what could be wrong?