68RFE Thermal Bypass Valve Delete Kit, 13-18 Ram 6.7 Cummins

A 2013-2018 Ram 2500 or 3500 with the 6.7L Cummins that shows climbing transmission temperature on a long grade, or a 68RFE cooler that a shop says will not flush clean, often traces back to one small part: the factory thermal bypass valve in the cooler circuit. This kit removes that valve from the equation. It is a billet 6061 aluminum body with cooling fins that installs in place of the stock bypass so fluid goes to the cooler full time, from cold start on.

What the thermal bypass valve does in a 68RFE

Hot fluid leaving the converter is supposed to go out to the cooler and back. On a cold engine, the factory valve holds that fluid away from the cooler so the transmission warms up faster. Sonnax describes how these thermal elements work: a wax-filled element pushes a pin out as fluid warms, at roughly 130 degrees F, to open the path to the cooler. If the pin does not extend fully, or extends and then creeps back, converter outflow never reaches the cooler, and the transmission and converter run hot. GEARS Magazine adds that when one of these valves sticks open on a 68RFE truck, a flush machine cannot clean the cooler at all. With the delete installed, there is nothing left in that path to stick.

Symptoms of a bad 68RFE thermal bypass

• Transmission temperature running past about 200 degrees F while towing or climbing, even with a clean cooler and good fan
• Temperature that keeps climbing in stop-and-go traffic or at idle in hot weather
• Dark or burnt-smelling ATF+4 sooner than expected
• Little or no flow out of the cooler return line during a flow test
• A cooler that will not flush clean or keeps sending debris back after a rebuild

How to confirm before buying

Heat on a 68RFE has several causes, and the GEARS Magazine checklist is a good order to work in: restricted cooler lines, a plugged cooler, a clogged filter, overloading, engine overheating and the electronic fan clutch. Check cooler flow at the return line; GEARS gives one gallon per minute as the minimum. If lines, cooler, filter and fan all check out and temperature still climbs, the bypass is the next suspect. Heat is also a symptom of slipping clutches, so if you have flare or slip as well, read our 68RFE Ram 3500 Cummins shift problems guide and the 68RFE Ram 2500 common problems guide before treating it as a cooling issue only.

Fitment

Listed for 2013-2018 Ram 2500 and 3500 with the 6.7L Cummins and the 68RFE. The cooler circuit hardware is not the same on every 68RFE truck: GEARS describes the bypass on an earlier 2008 truck as part of the cooler assembly itself, buried behind the grille, intercooler and condenser. Earlier and later trucks may use different parts, so compare your factory valve and line ports against this kit, or send us your year and VIN before ordering. All of our parts for this unit are on the 68RFE parts page.

Install notes

• The kit includes the bypass body, two O-rings, two retaining clips and a cleaning cloth.
• Clean the ports before fitting. Lube the O-rings with ATF and seat them gently; they nick easily on the cooler side, so keep a spare set on the bench.
• Make sure both retaining clips snap fully home, then check for leaks with the engine running.
• Top off with ATF+4 and set the level with the fluid hot.
• With full-time cooler flow, the lines and cooler can be flushed without needing hot fluid to open a valve.
• Know the trade-offs. Sonnax notes that blocking a thermal valve can affect shift quality and adaptation on transmissions that use temperature in their shift logic, and recommends synthetic ATF where temperatures fall below 0 degrees F. GEARS also warns that blocking the circuit can cause drain-back concerns.

If you tow heavy, pair this with more fluid capacity from a deep 68RFE aluminum pan kit. If you would rather run the valve-style upgrade, compare it with our 68RFE thermal bypass valve cooler kit.

Will this fit my 2016 Ram 2500 6.7L Cummins with the 68RFE?

Yes, it is listed for 2013-2018 Ram 2500 and 3500 6.7L Cummins trucks with the 68RFE. Compare your factory valve and line ports before installing, or send us your VIN if you want a second check.

Will deleting the thermal bypass make the transmission run too cold?

In most climates the cooler simply keeps fluid closer to normal temperature. It may take longer to warm up in winter. Sonnax recommends synthetic ATF where temperatures drop below 0 degrees F once a thermal valve is blocked open.

How do I know the factory bypass is the problem?

Rule out restricted lines, a plugged cooler, a dirty filter, engine cooling and the fan clutch first. If cooler return flow is low and everything else checks out, a stuck thermal bypass is the likely cause.

What fluid should I use after installing it?

ATF+4, the fluid this 68RFE calls for. Top off after install and check the level with the fluid at full operating temperature.

Does it change shift feel?

It can on transmissions that use fluid temperature in their shift program, because the fluid may warm more slowly. Most owners notice the steadier temperatures under load more than any change in shift feel.

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