Mishimoto 2017+ GMC 6.6L Duramax L5P Transmission Thermal Bypass Valve Kit
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
The Allison transmission is the backbone of your L5P Duramax. It's responsible for transmitting large quantities of torque from your V8 diesel powerplant. This torque generates a lot of heat, and if that heat isn't dissipated, it can destroy your transmission. The transmission cooler does a good job of keeping trans fluid temperatures in check, but only if the fluid can reach it. The stock cooling system of the Allison 1000 transmission utilizes an in-line thermal bypass valve that controls fluid flow to the transmission cooler. The purpose of this valve is to prevent transmission fluid from flowing to the cooler until it reaches operating temperature. The thermostat inside this valve is prone to failure, however, and when that happens, the fluid never flows to the cooler, and the transmission can overheat. That's why Mishimoto has developed a full-flow thermal bypass valve upgrade for your 2017-2019 Chevrolet/GMC 6.6L Duramax. Our CNC-machined aluminum full-flow thermal bypass valve not only looks better than the stock unit, but it performs better too. This Mishimoto thermal bypass valve eliminates the internal thermostat, providing full fluid flow to the transmission cooler in all running conditions. This setup is ideal for owners in warm climates, those performing heavy towing, and trucks needing the best possible cooling efficiency for their transmission. The Mishimoto thermal bypass valve features strategically machined internal passages, providing improved flow over the stock valve for more effective cooling. In addition, cooling fins machined into the valve body adds even more heat dissipation. This 2017-2019 Chevrolet/GMC 6.6L Duramax L5P Full-Flow Thermal Bypass Valve Kit is built to last a lifetime with a durable black anodized finish and our Mishimoto Lifetime Warranty.
- Durable CNC-machined billet-aluminum construction
- Eliminates failure-prone bypass valve
- Installs in less than 1 hour
Shipping information
We currently ship within the United States only. Most in-stock orders ship within 1 business day, and standard delivery takes 5-10 business days depending on your location. Shipping is calculated at checkout based on destination and item weight, and a tracking number is emailed to you once your order ships.
See our FAQ for full shipping details.
Returns & warranty
Returns are accepted within 14 days of delivery on new, unused, and uninstalled items in their original packaging. A 15% restocking fee applies, and a Return Merchandise Authorization (RMA) number must be requested before shipping any return. Some items are not eligible for return, including electronics, engine internals, turbo/supercharger kits, special orders, and Sale/Clearance items.
All products are covered by the original manufacturer's warranty. For returns or warranty help, email contact@sabaku-parts.com. Full details are in our FAQ.