Like pulling out the spare tire, tightening the bolts holding the air pump, checking on the Jack and handle to make sure they are in the Right slots not broken and thrown in the tire well. Is the battery locked down?
Next roller shade- still attached?

After pulling all that stuff out and confirming it is not causing the clunk and bonking, check the sway bar links and mounting brackets. There is a lot of stuff back there that might be step three.

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2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green