ok, well i get this question alot as well....

well what you can do is first check the diffs i know takes a little work to get to them...
but just to be on the for sure side check to see if there moving feely.....
if not you may need to shim them a little....
not likely but it can happen...
now they will "Feel" ok when on the truck because the tires are big and provide
"Leverage" to be able to turn the diffs while on the car
even with the wheels off turning the drive shafts are still helping.
only way to tell pull the diffs and check for free movement

also another reason is it vearing to one side or another is the diff is acting like a posi-rear end...
it will spin then "Lock" or unload then lock and this will happen......
so check the diffs make sure there moving freely and try running
i know everuyone might be going he's nuts!?!?!
but try running 5 to 7K in the rear and 10k in the center...
need more steering drop to 7k in the front...
did the same to both of mine and there pretty locked in!! wont wheelie as well
but better for cornering.....
ran mine with 5,7,5 at silver state and felt dialed!!! during practice!!!
but at last i decided not to run? and concentrait on the new truck and buggy