Manual hydro relief valves
 

I plan to remove the valves and send them to MachTech for rebuild. Can the tractor be pushed with the valves removed? Will oil shoot out? I do not plan to run the engine, just push. Thanks!

Good question. I would think not. In order for oil to shoot out, the Charge Pump would have to rotate.

No oil should come out other than any drain back from the control valve. They are ported directly to the case but with only the motor rotating group turning it won't displace any oil. After draining oil from the hydrostat, I remove the valves and fill the pump/motor case through the release valve ports, just as a precaution. Doesn't take much once the hydro/diff is filled to capacity.