It does creep with the key off. However I have pressurized both cylinders on the bench with one port open. They do not pass any oil in either direction. I guess the spool in the control valve must be allowing oil through when centered or I have a weak return spring.
I guess it's tear down time.

Thanks for the reply.

Does it still creep if you turn the key off?
if so, you have bad repacking of the cylinders. if not, it most likely will be in the valve.
This unit has a holding setup that when the operator is not in proper position to drive the truck, or the motor is not running, that will lock the hydraulics and not allow motion, and this setup is part of the main hydraulic control valve.