That's how i've set my steering, so the steering plate just touches the diff housing on lock. Any more than that and the servo makes funny noises
If one side is spinning freely and the other isn't, there must be some binding somewhere, do you have the spacer 310032 in your front hub on the LHS? Have you overtightened the wheel so the hex is dragging on the bearing (a possibility with plastic hexes) did you put all the seals/spacers/etc in the diff?
And the dragging/slow moving LHS wheel will cause the car to track oddly, no matter how well you set up the steering.