So far, here is whats been done-
1. New Differential
2. Swapped driveshaft, no results
3. Tightened motor mounts, transmission mounts, differential mounts, exhaust fittings, sway bar joints and mounts, shock absorbers, brake calipers, wheel lugs, swing arm pivots,
4. Checked frame for cracks, none found
This sound started abouth the same time as my transmission was changed, 2000 miles ago.
It clunks when stressing drivetrain, but its not the same sound as the drivetrain backlash. This sound is bigger, louder, more dramatic, and more noticeable. Seems to happen when two things are happening at the same time- Suspension is being flexed, AND, torque applied to rear wheels.
If the suspension is flexed, rolling over undulations in the pavement, but without any torque applied to the rear wheels, there is no sound, other than the very minor sounds of the chassis flexing.
If the car is on a level surface, and torque is applied, there is also no sound, other than the usual and typical drivetrain backlash.
But if you flex the suspension, AND apply torque to the rear wheels, the "clunk" sound rears its ugly head.
Theory- Although the differential is rigidly mounted, it is still subject to rotational forces, as the pinion gear tries to climb the ring gear. The effect of this force is transmitted to the differential mounting brackets, causing them to flex. As the differential moves slightly in its mount, the driveshaft spline going into the transmission is not allowed to accept the resultant slight fore-to-aft motion of the driveshaft, putting it in a bind, until the fore-aft-force overcomes the bind of the driveshaft under torque. Possible? Normally, I wouldn't suspect an obscure cause off the bat, but this one is not typical. No one seems to have any answers. Unless I can think of something else to chaeck, the car will go back to the shop for warranty repair. (Again)
