I’m not experienced with that model but most units of that vintage have a similar architecture. Yes, there are usually four relief valves for the wheel drives, one for forward and the other for reverse function for both wheels. They should look like large hexagon fittings on the main pumping unit close to where the wheel motor hoses attach to it.
It would be hard to determine which one is for which function without a detailed flow schematic, but you don’t need one to inspect them all. On some models the relief valves have a cone plug held in an orfice by a spring that can get pushed far enough out of the orfice that it’s tip of the plug gets out of the orfice.
As I recall you can remove these relief cartridges from the pump by unscrewing them, then check the inner surface of the removed part to see if the tip of the cone is inside the now exposed orfice. Chances are you will find one of those cones out of place. Put that relief cartridge in a vice and remove the hardware on the end of it to loosen the spring, and set the cone back in the proper position with its end in the orfice and then reassemble it all.
It’s also possible that a wear-plate has shattered inside the hydrostatic pump itself with what you describe. But if a wear-plate is intact but just scored, the system would likely shudder or pulsate when the bad wheel is under load. If the wear-plates need resurfaced or replaced (if you can get them) it’s a very intimidating and difficult assembly for most do it yourself mechanics.
Last edited by Haystack; 06-23-2019 at 07:49 PM.