Replaces the factory 68RFE thermal bypass valve on 2013-2018 Ram 2500/3500 6.7L Cummins so cooler fluid flows even when cold, cutting transmission heat.
If the transmission temperature on your 2013-2018 Ram 2500 or 3500 with the 6.7L Cummins climbs every time you hook up a trailer, even though the cooler is clean and the fan is working, the factory thermal bypass valve is a prime suspect. This kit is the billet ZeroStat replacement for that valve. It removes the thermostat element entirely, so fluid leaving the 68RFE always passes through the external cooler instead of being routed around it.
Chrysler put a thermostatic bypass in the 68RFE cooler circuit to bring a cold transmission up to temperature quickly. Below its opening temperature the valve sends returning fluid straight back to the case and skips the cooler; once the fluid is hot it is supposed to open fully and send everything through the cooler. GEARS Magazine describes exactly that intent, and notes that in hot weather the valve should be wide open. The weak point is that the valve can stick in the cold, bypassing position. When that happens the cooler is effectively out of the circuit, and a truck that tows will run hot on every grade. RevMax also states that the factory part carries an internal orifice that restricts cooler flow, and rates its ZeroStat design at about 87 percent more flow; treat that figure as the manufacturer's claim.
GEARS recommends working through the simple causes first: pinched or plugged cooler lines, a plugged cooler, engine cooling and the viscous fan. It also gives a useful rule of thumb: about 200 degrees F is the ideal maximum, and every 20 degrees above that roughly halves transmission life. With a warm engine, cooler flow should be at least one gallon per minute. If the lines and cooler test good, flow is weak and the fan engages, the bypass is the next thing to replace. If the truck also shifts poorly, read our 68RFE Ram 2500 Cummins common problems guide so you are not chasing a heat symptom that is really a pressure or clutch problem.
This kit fits the 68RFE six-speed behind the 6.7L Cummins in 2013-2018 Ram 2500 and 3500 pickups. It is the 2013-2018 design only: RevMax builds separate versions for 2010-2012 and for 2019-up trucks because the bypass hardware changed, so it will not bolt to those years. If you are unsure which cooler circuit your truck has, compare your factory bypass to the photos or send us your year and VIN before ordering. More parts for this transmission are on our 68RFE parts page.
If the transmission has already run hot for a long time, inspect the fluid and filter before assuming the bypass alone will fix it. Heavy friction material in the pan points toward a rebuild, and our ATSG 68RFE rebuild manual and accumulator piston and reinforced plate kit are common companions on a heat-damaged unit.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. This is the 2013-2018 design. The 2010-2012 trucks and the 2019-up trucks use different bypass hardware, and RevMax makes separate parts for those years.
Yes, somewhat, because fluid always flows through the cooler. GEARS notes the factory valve exists to speed warm-up in cold weather. Most towing owners accept that trade for steady cooler flow once working.
Rule out plugged lines, a plugged cooler and fan engagement first. If those are good but cooler flow is under about one gallon per minute and temperatures still climb, the bypass is the likely cause.
ATF+4 only. Top off after the install, then check the level with the fluid at 160 degrees F or more.
Usually not. The kit supplies the O-rings and clips for the bypass ports, and the green O-rings on the factory lines are meant to be reused unless damaged.
