[Brian_R]

Are you sure the ball shifter is assembled correctly? It sounds a bit like when you're putting the ball shifter in gear, you don't have full engagement of the balls. Check to see that the nut on the piston is positioned correctly.

If you take a look in the CAD model, the plunger that forces the balls into the inside of the gear is sort of wedge-shaped. If you didn't extend it fully, it might be gripping the gear a bit with friction that later slips under a more aggressive ball load. This may explain why adding pressure helps a bit but doesn't solve the problem (more force, more friction).

We are also using a ballshifter in a ratcheting winch - as a caution, we had issues getting the gearbox to shift into neutral under load with the stock pneumatic piston.

Hope this helps.