68RFE Thermal Bypass Valve Transmission Cooler Kit

The factory thermal bypass valve in the 68RFE holds transmission fluid back from the external cooler until the fluid is already hot. On a 6.7L Cummins that tows or works, that means the transmission runs warmer than it should during the exact conditions that make the most heat. This billet bypass replaces the OEM valve and lets fluid flow to the cooler at any temperature, so the cooler starts pulling heat the moment you pull out of the driveway.

It fits the 68RFE behind the 2013-2018 Ram 2500 and 3500 6.7L Cummins. Owners also report it dropping straight into the 66RFE. The valve seats in the factory bypass location on the case using the two supplied O-rings and two retaining clips, so there is no machining, tapping, or cooler-line rerouting.

Installation is a direct swap at the cooler line block. Pull the OEM bypass, seat the new billet valve with fresh O-rings, and clip it in. Because fluid now circulates through the cooler even when cold, you can flush the cooler lines with room-temperature ATF instead of renting a hot-flush machine. Real-world drops of 15 to 30 degrees on the trans temp gauge are common after the swap.

The body is machined from 6061 billet aluminum with integrated cooling fins that shed heat rather than trap it. The kit includes the valve, two O-rings, two clips, and a cleaning cloth. One tip from the field: always install with the new O-rings and top off the transmission fluid afterward, since a reused or nicked O-ring is the usual cause of a slow seep at the block.