I know this is an old thread, but hopefully someone can still acknowledge. I'm having g the same problem, I'm going to try a belt swap and see if that may help, maybe. But the funny thing is that the clunk doesn't happen "all" the time. Like if I am driving in forward, high or low, and switch into low or reverse after stopping it doesn't exist.. or.... if I lightly brake and start off there's nothing, no clunk, no play or whatever, just perfect... it's fricking weird and annoying.... you'd think with resistance from braking that it'd be worse. Tried forward, reverse forward and reverse with a light brake and no noise or anything. Without light braking, clunk.
Makes no sense to me...