is this caused by diff pull?

[lincpimp]

Check all of your shocks and make sure they all have the lower retainers, and that they all work without binding. That is usaully the cause for a pull, as the suspension can compress easier on one side than the other. I have had the same issue with just one of the 8 shocks on a maxx being damaged.

You may want to check all of your wheel bearings and driveshafts too. Any binding can cause erratic behavior.