SKU: 25597115635

Mishimoto 2017+ GMC 6.6L Duramax L5P Transmission Thermal Bypass Valve Kit

Sale price$89.95 Regular price$99.95
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  • USA
  • CAN

Ships within 48 hours · Estimated delivery Aug 9 - Aug 14

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Description

Mishimoto 2017+ GMC 6.6L Duramax L5P Transmission Thermal Bypass Valve KitThe 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

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+ 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 add even more heat dissipation. This 2017+ 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.
Shipping Notes
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Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
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SKU: 25597115635

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A. Walther
Lowell, US
★★★★★ 4
Get lots of compliments.
Size: X-Large, Color: Blue
These are awesome! I get lots of compliments. I took out the string/rope belt and just wear a regular belt because the rivets look cheap but it works.
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Reviewed in the United States on December 16, 2025
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Neva
Massapequa, US
★★★★★ 5
I got ripped off
Size: Large, Color: Blue
Loops were missing for belt. I returned for a different pair hoping it was a defect. Received another with the same problem. The denim ones have 6 loops. The white have only 4. So impossible to loop correctly. After I received the second pair they charged me for the ones I returned. So I paid for 2 pairs only kept one
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Reviewed in the United States on February 15, 2026
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Midwest Mama
Lexington, US
★★★★★ 2
High waisted, heavy duty, no stretch jeans
Size: X-Large, Color: Blue
I liked them, except they were high waisted which are not a good look for me.
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Reviewed in the United States on May 13, 2026
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Kristen Noelle
West Palm Beach, US
★★★★★ 5
Cute, comfortable and stylish jeans
Size: Small, Color: Blue
These jeans are so cute! They are on the thicker, stiffer size. I got a lot of compliments on the patchwork jeans. They did arrive with a very strong sort of chemical odor. I washed twice before I wore them.
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Reviewed in the United States on May 15, 2025
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jean
Louisville, US
★★★★★ 5
Very cute, but too big for me.
Size: Small, Color: Blue
Very cute, great quality but too big for me. Had to return. For reference I’m 4’11’’ & 105lbs
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Reviewed in the United States on May 27, 2025

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