Fits 88-03 4 Speed 500, 518 and 618 Heavy Duty Trucks including High Performance Trucks Fits early model 42-47 RH with hydraulic/mechanical governor or later model RE with electronic governor pressure solenoid and transducer. Does not fit 03-up 48RE Includes our exclusive governor pressure and throttle pressure limit systems for an increased range of tuning options. You will really like how it installs and works. Perfect for towing! Upgraded with New TCC Boost tuning plate added 2016. New Manual valve, TCC boost valve bracket, Mumbly Peg for easy rooster comb assembly and items for corrected unit calibration. Addresses Converter slip-shudder. Leaks out vent or lever. Front bushing and seal burnup. Drainback Complaint Features Instant full-race and includes our Gear Command feature for upshifts and downshifts at any speed/rpm. We do not recommend utilizing the Gear Command feature in Diesel engine equipped vehicles. Installation recommendation: Experienced technician Transmission removal necessary: No