DEX210 Slipper or Diff Problem

[Axeboy]

Hi Guys

Been slowly building my DEX210 kit and its almost done but has a bit of a problem.

Basically the power from the motor is making it to the spur ok, but almost nothing in the wheels. Well, when I say nothing, they will turn off the ground but on the level it sits almost on the spot, maybe moving a touch.

The slipper seems fine but I can only assume its the ball diff. I followed the guide on building it as well.

Any advice on the tightness of the ball diff screw? And also, the tightness of the slipper in-case I'm doing anything here too?