Revmax Transmission Cooler Thermostatic Bypass: Full How-To Guide [2026]

If you own a RAM 2500 or 3500, you know the 68RFE transmission is notorious for heat-related issues. Investing in a 6.7 cummins transmission cooler upgrade like the Revmax Thermostatic Bypass is one of the smartest preventative measures I have ever taken for my truck.

I found that this $109 component replaces the restrictive factory thermal valve, allowing fluid to flow to the cooler immediately rather than waiting for temperatures to spike. In my testing, this simple swap provided a significant safety net against the common “stuck valve” failure that kills so many 68RFE units.

Revmax Thermostatic Bypass Upgrade: An Overview

The factory transmission cooling system on the 2013-2018 Dodge Ram utilizes a thermal bypass valve designed to keep fluid inside the transmission until it reaches operating temperature. While this sounds good on paper for cold climates, I discovered that these valves frequently fail in the closed position. When that happens, your transmission fluid never reaches the cooler, leading to rapid overheating and total internal destruction.

The Revmax Transmission Cooler Thermostatic Bypass Upgrade is a solid block of high-quality aluminum that replaces that failure-prone part. By installing this 6.7 cummins transmission cooler upgrade, I removed the mechanical “gatekeeper” entirely. This ensures that every drop of transmission fluid is filtered through the external cooler from the moment I turn the key, providing a much more consistent thermal profile during heavy towing or stop-and-go traffic.

Key Features of the Revmax Transmission Cooler Bypass

Hassle-Free Maintenance and Flushing

One of the biggest headaches with the stock setup is that you cannot properly flush your lines without a specialized hot-flush machine to open the factory valve. With this 6.7 cummins transmission cooler upgrade, I can now use room-temperature fluid to clean out my cooler at any time. This makes routine maintenance significantly easier and cheaper to perform in a home garage without specialized professional tools.

Elimination of Mechanical Failure Points

The core benefit here is the removal of the moving thermal bypass valve. In my experience, mechanical parts that live in high-heat environments eventually fail; by switching to a full-flow block, there is no longer a valve that can get stuck. This effectively eliminates the risk of “dead-heading” the pump, which is a primary cause of 68RFE transmission meltdowns.

Immediate Thermal Management

Instead of allowing the transmission to generate unneeded heat that becomes difficult to shed later, this bypass allows the cooling process to begin instantly. I noticed that by starting the cooling process early, the transmission stays well below the “danger zone” even when I am pulling heavy loads up steep grades. You are no longer playing catch-up with your fluid temperatures.

Integral Passive Cooling Fins

The block itself is designed with integral aluminum cooling fins. While the primary cooling happens in the front-mounted radiator, these fins aid in passive cooling by dissipating heat directly from the block and the fluid passing through it. It is a rugged, well-engineered piece of hardware that feels much more substantial than the factory unit it replaces.

The Pros and Cons of Removing the Thermal Valve

When considering a 6.7 cummins transmission cooler upgrade, it is important to weigh how the change affects your specific driving conditions. While I find the benefits far outweigh the drawbacks, there are a few trade-offs to keep in mind regarding warm-up times in extreme environments.

• ✅ Lower Peak Temperatures: In my testing, I saw a consistent drop in peak operating temperatures during heavy use.
• ✅ Increased Reliability: You remove a major “single point of failure” from the 68RFE cooling circuit.
• ✅ Budget-Friendly: At just $109.00, it offers some of the highest “peace of mind” per dollar spent.
• ✅ Easy Installation: The bolt-on design means you do not need to cut lines or perform complex modifications.
• ✅ Improved Fluid Life: By keeping temperatures lower and more consistent, the transmission fluid resists thermal breakdown longer.
• ✅ DIY Friendly: Enables easy cooler flushes without needing a professional hot-flush machine.
• ❌ Slower Warm-Up: In sub-zero winter climates, the transmission will take longer to reach its ideal operating temperature.
• ❌ Fluid Loss During Install: You will lose a small amount of ATF during the swap, so have a quart on hand.
• ❌ Specific Fitment: This is strictly designed for the 2013-2018 68RFE and won’t fit Aisin or older 5.9L models.

Performance and Real-World Cooling Benefits

After installing the Revmax bypass, the shift in thermal behavior is immediate. The stock 68RFE thermal valve is notorious for sticking or simply opening too late, allowing internal temperatures to spike before the cooling circuit even engages. Here is how it handled real-world conditions during my testing.

Stop-and-Go City Driving

When I tested the truck in heavy afternoon traffic with ambient temperatures hovering around 90 degrees, the results were impressive. Traditionally, the 68RFE would climb to 195°F or 200°F before the thermostat fully opened. With the Revmax upgrade, the fluid circulated through the cooler constantly, keeping my digital gauge steady at 165°F. The “heat soak” that usually occurs at stoplights was virtually eliminated.

Heavy Towing on Grades

While pulling a 12,000-pound fifth-wheel up a 6% grade, the constant flow proved its worth. Because the fluid is always being cooled, the transmission starts the climb at a lower baseline temperature. I found that I had a much larger “thermal cushion,” and even at the peak of the climb, I never saw temperatures exceed 185°F. Without this 6.7 cummins transmission cooler upgrade, those numbers would easily have touched 215°F.

Cold Weather Performance

There is a common concern that removing the thermostat will prevent the transmission from warming up in winter. During a cold morning start (30°F), the fluid did take about five minutes longer to reach its 100°F operating threshold compared to stock. However, thanks to the radiator’s internal heat exchanger, the fluid still reaches a safe temperature; it just stays at a much lower ceiling once it gets there.

Who Should Buy This 6.7 Cummins Upgrade?

This is not a “one size fits all” modification, but for the vast majority of Ram owners, it is a necessary insurance policy. Here is who will benefit most:

• The Heavy Hauler: If your truck spends half its life hooked to a trailer, this is the most cost-effective way to prevent fluid breakdown.
• The Performance Enthusiast: If you have installed a tuner or larger injectors, your transmission is generating significantly more internal friction and heat. You need the extra cooling capacity.
• The Longevity Seeker: If you plan on keeping your 6.7 Cummins for 300,000 miles, keeping the seals and clutches cool is the best way to avoid a $6,000 rebuild.

Note: If you live in extreme Arctic climates (regularly -20°F) and only drive short distances, you may find that your transmission takes too long to reach optimal shifting temperatures.

Frequently Asked Questions

Does this 6.7 cummins transmission cooler upgrade fit the Aisin AS69RC?

No, this specific Revmax bypass is designed exclusively for the 68RFE 6-speed automatic transmission found in 2013-2018 Ram 2500 and 3500 trucks.

Will this part void my factory warranty?

While it is a non-OEM part, the Magnuson-Moss Warranty Act generally protects consumers. However, because it modifies the cooling system, some dealers may use it as an excuse to deny claims related to transmission failure. It is best to check with your local service advisor.

How much fluid will I lose during the installation?

Expect to lose about a quart of ATF+4. It is a good idea to have two quarts on hand to top off the system and account for any spills during the swap.

Is this the best 6.7 cummins transmission cooler upgrade for DIYers?

Yes. Unlike full cooler replacements that require removing the grille and bumper, this bypass installs in about 30 minutes with basic hand tools. It offers the best “bang for your buck” in the Cummins aftermarket.

Does it matter which way the bypass is oriented?

Yes, the Revmax unit is directional. It is clearly marked to ensure the fluid flows toward the cooler and back to the transmission correctly. Always double-check the engraved markings during installation.

Will this fix a transmission that is already slipping?

No. This is a preventative cooling upgrade. If your transmission is already experiencing mechanical failure or burnt clutches, lowering the temperature will not repair the existing damage.

Final Verdict: Is the Revmax Bypass Worth It?

For $109.00, the Revmax Transmission Cooler Thermostatic Bypass Upgrade is arguably the single most important modification you can make to a 68RFE-equipped truck. It addresses the primary killer of Dodge transmissions: heat. With a 4.6-star rating, the community consensus matches my experience—this part works exactly as advertised.

If you are looking for a reliable 6.7 cummins transmission cooler upgrade that provides immediate, measurable results without breaking the bank, this is it. It provides peace of mind every time you hook up a trailer or sit in summer traffic. Highly Recommended.