my buddy just called me and ask y his back tires feel so loose he said that it not his barrings sounds to like its his pillow balls? I dono I'm new to the revo and I haven't had to fix that yet. Since I bought a used one and sold it to him figured I could help him fix it (not that I wouldn't help him anyway). So what should we do first try to fix the pillow balls or just buy new hubs???? I haven't really looked in to it yet but thoght this would be a good first step
If the wheel nuts are tight like they are supposed to be and there is still play then next on this list would be "pivot" balls. Tighten them up until there is no play but the wheels turn freely and the suspension doesn't drag. If that doesn't solve your issue then the last thing to check is the grub pin that holds the hub to the stub axle. When you take the wheel nut off and remove the wheel you will be at the hub. If you look closely you will see that there is a pin holding that on. It goes all the way through the hub. If it is loose then you will need to fix the problem there and this can cause loose wheels. This is what was always the problem for me and i bet is your problem. Tightening the screw wont fix it either. What happens is the pin that holds the hub on goes through the stub axle. Over time it wears the pin down and the stub axle. So you will need to replace the pins and the stub axles.
A easy way to tell if its the stub axle and pin problem is while the wheel is on look at the end on the hub. try rocking the wheel in and out. If you see the hub moving but the end of the stub axle is not moving then the pin and stub axle are bad.
