I have an RS4 3 SS. I was running it today, and there seems to be a problem, where the car (im not sure if its the diff, or maybe the 2-speed, might also be the brake disc) keeps stiffening, and the car can barely move if pushed. But then after a while, the car runs normal and has no problem, it feels normal. The problem keeps happening, and it stiffens, and a few minutes later, it feels find. Can someone please tell me whats wrong. I am probably going to rebuild most of the car, but I just want to know what to look for.