[RC-Monster Mike]

If you are using servo mounted servo savers then that is most likely the problem - they don't make those things stiff enough to handle the torque load your setup dishes out. I suggest finding a UE servo saver or even the Proline version(I have a couple around if you need one) - the bellcrank saver design is far superior to the old school 1/10 servo mounted pieces of crap. To verify whether or not the savers are the problem, simply remove them and replace with solid servo horns(try not to hit anything when testing). If the truck suddenly drives straight, then search for the savers mentioned above. :)