when you change directions from forward to reverse it makes a clunk sound and there is a slit delay in movement.
it may be the rear tranny mount
you probably need motor and/or transmission mounts
Possibly a worn out universal joint.
Worn out bushing or steering joint probably.
Possibly weak u-joints or transmission mounts
check engine mounts
I am not sure what you mean by rear, but here are some possibilities. It could be bad u-joints if it makes the sound right when you put it reverse it will could also make it when you put it in drive. If you have the automatic 4L60-E transmission and i only heard this once that the reverse input clutch was so messed up that it made a clunking sound.
This happens on my 2002 mk5 fiesta. The front brake pads move very slightly in the caliper, so when you reverse and apply the brakes you'll hear a slight clunk. I had this repaired by ford as my car was under warranty - replaced pads and noise went away.
Most likely a CV joint...could be dangerous... consult a mechanic asap
Copper produces a dull thud or clunk sound when it is struck. The sound may vary slightly depending on the thickness and shape of the copper object.
the biggest crate motor GM chevy makes is a 572 not a 502