68RFE Thermal Bypass Valve

Why Does Your 6.7L Cummins 68RFE Need a Thermal Bypass Valve?

Thermostat Stuck Closed, No Cooler Flow

The factory valve is a tiny spring-loaded thermostat that is supposed to open near operating temperature.
When scale, heat fatigue, or a fatigued spring holds it shut, the cooler circuit is dead and your fluid temperature climbs with every mile.

Fluid Oxidation and Clutch Glazing

ATF that runs above 200 degrees Fahrenheit breaks down fast, losing its friction modifiers and varnishing the valve body.
Glazed clutches and sticky solenoids follow, and a full rebuild is the next stop.

You Cannot Flush a Hot Thermostat

A stuck valve blocks cooler flow until the unit is hot, so a normal flush pushes clean fluid in circles.
Full-flow cooling lets you exchange fluid properly at any temperature and actually clean the cooler circuit.

What Can a Thermal Bypass Valve Solve?

Constant, Unrestricted Cooler Circuit

The 6061-T6 billet aluminum full-flow body removes the thermostat entirely and sends fluid through the cooler the instant the pump spins.
Hardened stainless passages and Viton O-rings hold pressure without the spring fatigue that plagues the factory unit.

Lower Sustained Temperature and Longer Fluid Life

Drops of 30 to 40 degrees Fahrenheit are common under tow, which keeps the ATF in its operating range and protects the clutches, seals, and torque converter.
Cleaner fluid means longer service intervals and a transmission that holds up to heavy use.

Proper Serviceability

With full flow restored, you can flush and refill the 68RFE correctly, and the cooler does its job every time the truck moves instead of waiting on a stuck thermostat.

Shop 68RFE Thermal Bypass Valve by Ram Cummins Engine & Fitment Guide

• Transmission Cooler Thermal Bypass - Fits the 6.7L Cummins (68RFE) in Dodge Ram 2500 and Ram 3500 (2013-2018). CNC-machined 6061-T6 billet aluminum full-flow body with Viton O-rings that replaces the stuck factory thermostat and restores constant cooler flow. Direct drop-in on the driver-side cooler line.
• Thermal Bypass Valve (Billet Coupler) - Fits the 6.7L Cummins in Ram 2500 and Ram 3500 (2019-2024). Full-flow billet aluminum coupler sized for the 2019-up body style and cooler-line layout, with hardened stainless internals and a corrosion-resistant anodized finish.

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What does a 68RFE thermal bypass valve do?

The factory thermal bypass valve is a small thermostat in the 68RFE transmission cooler circuit that holds automatic transmission fluid inside the transmission until it warms past roughly 170 to 190 degrees Fahrenheit.
Its job is to speed up warm-up for cold-start efficiency, then open so hot fluid can circulate through the cooler.
When that thermostat fails and stays closed, the cooler circuit is cut off and the fluid temperature keeps climbing.

Where is the 68RFE thermal bypass valve located?

On the 2013 and newer Ram 2500 and 3500 with the 68RFE, the thermal bypass valve sits in the cooler line assembly on the driver side of the transmission, up near the fuel filter housing area.
It is an inline piece in the pressure line that feeds the auxiliary cooler, so you are looking for a small metal valve body spliced into the hard lines on that side.
The 2019-up trucks use a revised cooler-line layout, which is why the replacement valve and coupler are sized differently for that body style.

What are the symptoms of a bad 68RFE thermal bypass valve?

The classic sign is a transmission temperature gauge that runs high or climbs steadily even when you are unloaded, because the stuck-closed thermostat blocks the cooler circuit.
You may also notice burnt-smelling or dark fluid, harsh shifts as the fluid thins out, and a transmission that runs noticeably hotter after a tow.
Because the valve blocks cooler flow until the unit is hot, a stuck valve also makes a proper fluid exchange nearly impossible.
If your temperature stays pegged above 200 degrees Fahrenheit on the highway, suspect the thermal bypass before the cooler itself.

Why upgrade to a full-flow 68RFE thermal bypass valve?

A full-flow billet aluminum bypass removes the failure-prone factory thermostat entirely and sends fluid through the cooler the moment the pump turns.
Owners routinely report transmission temperatures dropping 30 to 40 degrees Fahrenheit under load, which keeps the ATF, clutches, and seals in their operating range.
Constant cooling is especially valuable on trucks that tow heavy, run tuned, or work in hot climates where the factory thermostat simply cannot keep up.

Will the 68RFE thermal bypass valve fit a 2008, 2011, or 2012 Ram 2500/3500?

EGR Performance stocks two direct-fit thermal bypass parts, a Transmission Cooler Thermal Bypass for the 2013-2018 Ram 2500/3500 and a Thermal Bypass Valve for the 2019-2024 Ram 2500/3500.
The earlier 68RFE trucks used a different cooler-line arrangement, with 2010 through 2012 running the Mopar 52014523AB valve assembly and the 2007.5 through 2009 trucks using an internal bypass built into the front cooler rather than a separate inline valve.
Because of that layout difference, there is no matching drop-in EGR SKU for a 2008, 2011, or 2012 truck, so confirm your model year and cooler-line setup before ordering.

What is the difference between the 2013-2018 and 2019-2024 68RFE thermal bypass?

The two parts cover the same job, restoring full-flow cooling on the 6.7L Cummins 68RFE, but they are sized for different Ram body styles.
The Transmission Cooler Thermal Bypass is the direct-fit full-flow piece for the 2013-2018 fourth-generation Ram 2500 and 3500, machined from 6061-T6 billet aluminum with Viton O-rings.
The Thermal Bypass Valve, shipped as a billet coupler, matches the revised cooler-line routing on the 2019-2024 Ram 2500 and 3500.
Pick the one that matches your truck's year, since the line geometry changed with the 2019 redesign.

Does the 68RFE thermal bypass fit the Aisin AS69RC or HO Cummins?

These thermal bypass parts are built around the 68RFE transmission used behind the standard-output 6.7L Cummins in the Ram 2500 and 3500.
The Aisin AS69RC behind the high-output 6.7L Cummins in 3500 cab-and-chassis and certain pickups uses a different cooler-line layout, so it is not a guaranteed drop-in for that transmission.
If your truck runs the Aisin, confirm the cooler-line configuration before ordering rather than assuming the 68RFE part will fit.

What is the best 68RFE thermal bypass valve for towing?

The best choice for a tow rig is a full-flow billet aluminum bypass that deletes the factory thermostat and moves fluid through the cooler continuously.
Look for a CNC-machined 6061-T6 body, hardened stainless internals, and ATF-compatible Viton seals that will not fatigue the way the OE spring does.
The EGR Performance full-flow parts for the 2013-2018 and 2019-2024 Ram 2500/3500 hit all of those marks and are direct drop-ins, which is why most heavy-tow owners treat this as a do-it-first upgrade.

Is the 68RFE thermal bypass valve street legal?

A thermal bypass valve is a transmission cooling part that removes a fluid thermostat, not an emissions device, so the part itself is a street-legal cooling upgrade in all 50 states.
The "competition and closed-course off-road use only" label attaches to trucks that have been emission-deleted or performance-tuned for competition, so check your local jurisdiction before pairing it with a deleted or tuned build.
Confirm your model year, 2013-2018 or 2019-2024, before ordering so you get the correct cooler-line fitment.
Every order includes free shipping, is backed by a 1-year warranty, and comes with our 45-day return policy.

How do I install the 68RFE thermal bypass valve?

Installation is straightforward on the driver-side cooler line near the fuel filter housing.
Let the truck cool, drain a small amount of ATF to avoid a mess, then unbolt the factory valve from the cooler-line assembly and swap in the full-flow billet piece with fresh Viton O-rings.
Top off the fluid, start the truck, and cycle through the gears to bleed the circuit.
It is a hand-tools job that most owners finish in well under an hour, though you can flush the transmission at the same time since the full-flow circuit makes that possible at any temperature.