Tried this before to no avail, maybe if I explain it better, I'll come up with a solution.

Relatively stock '87 4Runner, 22RE, W56 tranny, ADD front end. Recently had a rear u-joint fail, dropping the driveshaft at 60MPH. Replaced both front yokes on rear shaft, but while running around for parts, I used front wheel drive - for a total of maybe 45 miles.

Since replacing the rear shaft and resuming "normal" operation, the truck clunks when reversing. It will continue when I start forward again and usually goes away with a few rotations. The sound seems to be coming from the right front side of the drivetrain and is directly tied to the wheel rotation.

My first guess is the ADD system, perhaps it's engaging or partially engaged causing the sound. Anyone have any suggestions or ideas on what to check, It's beginning to drive me nuts...