At this point I would take SSdoxies advice to cap and plug one of the two in out supply lines then operate your control lever to that motor. If the engine bogs down and you hear the relief valve open and squeal odds are you've got good flow and pressure to the motor indicating that your drive motor is at fault. The other thing that you absolutely should do and is easy is pull the case drain filter and see what you find. I think it's located under the right side shroud but not sure, it's a small sintered bronze filter inside a small canister maybe 11/2" in diameter. Very important to replace this filter anyway. There is engineered leakage from your drive motors that flow through this filter on way back to supply tank , if it plugs up it can destroy your drive motors/final drives. Let us know. B