Hydraulically controlled power transmission having friction plate clutches for selectively engaging a plurality of change speed gears

摘要

A hydraulically controlled transmission for vehicles such as heavy-duty, high horsepower, off-highway trucks, the transmission having a plurality of selectively engagable change speed gears and hydraulically actuated friction type clutches for selectively engaging the gears to provide various speed ratios for the vehicle. The transmission includes a hydraulic control circuit in communication with the clutches and a rotary range selector valve is located in the circuit and driven in step-by-step increments by a geneva wheel drive means. The arrangement insures that the transmission can be shifted at only one speed range at a time and that an engaged speed range will be released before another speed range is engaged.