The guide valve is just what the shift lever hooks as many as. According to which gear is chosen, the guide valve feeds hydraulic circuits that inhibit certain gears. For instance, In the event the shift lever is in 3rd gear, it feeds a circuit that prevents overdrive from partaking. https://gearbox-auto10851.theobloggers.com/40407989/5-easy-facts-about-gearbox-auto-described