I just recently bought new front and rear differential for my Revo. And now it seems to have no power to the rear tires. If I pick the rear end up off the ground and give it gas it spins the tires, but as soon as there is any load on it, it will not turn the wheels. I have checked the drive shafts, made sure the tires are properly installed, the slipper clutch is tight. I have even tried putting my old differential back in and it does the same thing. I am starting to think that it might be my center differential going bad. Is there any way to test it to see.