RTV 1100 Move Slow - Then Stops

[dtreid]

New to me RTV 1100

Will drive forward and reverse up until maybe 20% throttle pedat movement. Anything beyond that and it stops moving like the hst pressure dumps. If I come back to idle it will move again.
Jacked up the back wheels and disconnected the servo rod so that I could run the wheels at idle. After about 20% servo lever movement the wheels stop. Below 20% servo lever movement the wheels start turning again.

This is a new one for me......back check/relief valve?

 

[dtreid]

Changed oil and filters - no change

Pulled out forward and reverse relief valves - no issues seen

Pulled charge pump check valve - no issues apparent.

Any other ideas?

 

[Doc]

Sorry, no ideas at all. Never heard of an issue like yours. sure will be interesting to see the solution. Wish I could help.

 

[dtreid]

Got it fixed. Took the hst apart to find the front motor pistons badly worn. The face of them were pounded out flat not convex like they are supposed to be.