I installed the HR spiral diff today, shimmed it up, its very smooth, much easier than I anticipated from reading some of the comments on this forum. There is no way its clicking from there, if it is, traxxas is selling some defective parts as the rear bulkhead is brand new. I checked the bearings and they are good. My only thought at this point and I was thinking this before putting the hr diff in is that the internal gears are stripped in the diff. could that cause the clicking noise?
Right now as I posted in another thread, if I spin one wheel, the other wheel spins normally, but if I spin the other wheel, in one direction, it usually works, the other way is locked solid. when I put a lot of force on the locked solid wheel, I could get the diff to skip a tooth, but I can't imagine the ring and pinion could be the problem as I shimmed them up nicely and threw an extra shim in for good measure. It still turns very nicely, nicer than the stock traxxas diff ever did. So I think it could either be the internal gears in the diff or maybe a bad rear center shaft? When I drive in reverse it works fine.