Thanks for your information.. The RTV has an additional hydraulic pump that appears to be mounted to the engine block behind the injector pump. Most likely to power the Kubota 72" commercial snow plow. I'm going to see if it might play a role in all this.
The power steering/bed tilt pump is mounted behind the injection pump. If an auxiliary hydraulic package is added, that pump is replaced with a tandem pump. The front section supplies the steering and dump bed & the rear section supplies the auxiliary hydraulic control valve.
This pump draws hydraulic oil from the reservoir under the passenger seat.
if you are leaking oil from the transaxle into the bell housing, check the vents on top of the transaxle. If they are plugged it will push oil past the transaxle input shaft seal into the bell housing.
For the oil to get from the bell housing into the engine crankcase, the bell housing would have to fill up to the height of the rear crankshaft seal and be pressured higher than the engine crankcase pressure.
The transaxle oil is just for lube, there is no pump. The hydrostat is mounted to the rear of the transaxle assembly and it draws oil from the reservoir under the passenger seat.