On certain Chevrolet, GMC, and Cadillac trucks and SUVs, when the transmission overheats, doesn't generate sufficient heat, or leaks fluid, it can be due to the failure of the original equipment transmission bypass valve. The factory valve design is notoriously vulnerable to corrosion, clogging, and wax motor failure, design flaws reflected in a GM service bulletin (Chevrolet TSB 21-NA-199). This direct replacement Dorman OE FIX valve is upgraded to more effectively optimize cooler and transmission performance and provide a more permanent repair. Machined from solid aluminum billet for enhanced corrosion resistance, the housing features a threaded cap that protects the bore and seals and eliminates the OE snap ring design, which is prone to corrosion that can lead to complete system failure. And to make routine service more convenient, it includes an additional access port.