6.7L Diesel
On all models equipped with an automatic transmission, the transmission oil is flows through an externally mounted oil-to-air Transmission Oil Cooler (TOC) where heat is removed from the transmission oil before returning to the transmission. The transmission oil exiting the torque converter flows through the TOC supply line (1), into the end tank TOC, through the external cooler and then back to the transmission sump through the TOC return line (2).
The transmission oil cooling system contains a dual function bypass valve (3) between the transmission and the transmission oil cooler. The bypass valve (3) will bypass the transmission cooler when the fluid temperature is below 70°C (158°F) to aid the transmission fluid to reach operating temperature. The thermal bypass begins opening at 70°C (158°F) and begins allowing fluid flow to the transmission cooler, and is fully open when the transmission fluid temperature reaches 81°C (178°F).
The bypass valve also will start to open if the pressure in the transmission cooler circuit exceeds 3.42 bar (50 PSI).
The bypass valve is a serviceable component.