I really don't think it's the servo. I have the updated one on mine, the wheels turn, but the car doesn't![&o]
Once I get the rear bulkhead replaced, I am gonna get some 25 degree castor blocks and see what kinda difference that makes. If that isn't enough, I'm gonna try to mod the front shock tower, in order to place the shocks behind it to lower the centre of gravity like the e-rustler
over here. Still love my Rustler though!