Hi, when I try to roll my Stampede 4x4 on the ground it barely even rolls? I have pulled the rear end off to inspect. Nothing obvious. Have pulled put slipper, front and rear diffs for inspection, no issues found. I can roll back wheels and front wheels by themselves easily but when I try to roll the car on its four wheels, it hesitates and struggles like something is stopping it. If it is on 4 wheels and i try to push it with light force forward, it doesn't move without a heavier push. I dont know why i am suspecting something with the slipper clutch but I've just upgraded this to the heavy duty Traxxas one that uses steel pads. Was having the problem just before i replaced the standard pede4x4 slipper as well. The car is a month old and hasn't been through dirt or water, mainly grass and road. Any help would be much appreciated. I am relatively new to this hobby so it could be obvious to the experienced, but I have no idea what is causing it. Cheers Paul