DMaxx

I recently bought a Losi Mini T 1/18th scale truck and it seems that there is something wrong with the differential. You can sometimes pull the trigger on the remote while pushing down on the truck and nothing happens but when you let the truck up after releasing the trigger the back wheels run...almost like it was winding itself up. And it sometimes won't stop going in forward after I let up on the trigger. I put a brand new speed control on it and that didn't fix the problem. I am stumped. If it is in the transmission, does anyone know what to do? Or any schematics of it? Or anyone to send it to to have it fixed? Thanks....