What could be causing a popping / clunking sound from the rear end of a 1996 Caprice? The sound is only present (or apparent at least) after the vehicle has been driven for a while and seems to correlate with the brakes being gently applied or backing up. Anything I should check besides the differential and the rear drum brakes?
I should mention the vehicle has a torque converter with a higher than stock stall speed that went in with a fresh 4L60E. There is no torque creep to speak of and there is a bit of a whiplash effect when accelerating from a stop with a heavy foot on the gas.
The differential (G80 RPO) was low on fluid. It was leaking out of the pinion seal, which is a common problem on this generation of this platform. Fluid has been changed and the seal replaced. The noise has changed, but it's still there. Not as many pops/clunks, and the frequency has slowed, too. I wonder if the fluid was low enough long enough to damage the rear end? I suppose it could be age related, too. It's probably the original rear end, and it has over 150,000 miles on it. Front and rear brakes appear to be good.
The sound is present when letting off the brakes after a stop after driving at highway speeds.