The Grand Lxx30 series tractors have a main dry clutch on the FST, GST and HST transmissions but the GST also has electro hydraulic forward reverse wet clutch packs. The shuttle lever controls the forward and reverser but the gear selector is just a POT that goes to the GST box and it reads resistance and tells what hydraulic actuators need to be activated to shift the gear forks and then activate the clutch packs. If the ECU dies there are plugs by the right rear of the seat to plug together for putting tractor to one gear for moving. If the hydraulic flow to the transmission fails do not think there is anything you can do if the hydraulic pump or regulator valve goes as the clutch packs need fluid to run. There is a TSB for the Grand Lxx30 tractors about extended idling such as using a backhoe in a certain angle that will starve the hydraulic pump of lubricating oil and a bearing fails, seizes pump and breaks thing. The fix is a kit with new oil filter base, pump holder and an oil line going between the two so that there is pressure lubrication to the bearings