Hi Ron,
The hydraulic oil reservoir and gearbox are separate; the hydraulic oil is located in the space above the gearbox. You can refill the hydraulic oil through the filler cap behind the seat.
Whether you have the Agriomatic gearbox or the standard gearbox, the Agriomatic can be recognized by the filter on the left side of the gearbox near the clutch pedal and the control lever on the right side of the dashboard where the hand throttle lever is also located. Only IH Hytran may be used in this gearbox. The regular gearbox can be filled with SAE 90. The level plug is located on the left side under the clutch pedal, just like on an M or H. The filler plug is located just behind both gear levers.
The gearbox oil must be drained at two locations under the tractor: under the gearbox and under the differential.
Both axles have their own oil reservoir filled with SAE 90 oil. The drain plug is located on the gearbox side near the brakes. The new oil must be filled through the plug located on the wheel side.
Between this oil reservoir and the gearbox are the brakes, which are double disc brakes similar to those on a Super M.
In the past, someone posted the manuals for this engine on this forum, but I can't find them.