PPE Diesel 125070000 Fluid Thermal Bypass Valve For 19-23 Silverado/Sierra 1500Transmission Fluid Thermal Bypass Valve Add another measure of protection and increase fluid flow to the transmission cooler. Increase cooling capacity with this easy to install billet aluminum PPE Transmission Fluid Thermal Bypass Valve for the GM 8L90 8 Speed transmission. The OEM part has restrictive internal passages. When the OEM valve fails in the closed position, transmission fluid doesn't reach your cooler. This can be caused by mechanical