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 Jul 27 - Aug 1

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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.
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SKU: 25597115635

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saintiva paul
Omaha, US
★★★★★ 5
Nice evening clutch
Size: One Size, Color: Pale Gold
Nice and elegant
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Reviewed in the United States on January 16, 2026
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Elsa Sigua
Boise, US
★★★★★ 5
Perfect and good quality
Size: One Size, Color: Silver-tone Hardware/Black
I liked it so much😍
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Reviewed in the United States on December 29, 2025
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Felicia Gardner
West Palm Beach, US
★★★★★ 5
Comfortable
Size: 8, Color: Natural Snake
These shoes are cute, and go with most everything. They are comfortable and can be work for while without having any issues. I was a bit worried they might rub blisters but have not had that problem with these. The heel and fit of them are perfect. And they are versatile. Worth the price.
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Reviewed in the United States on May 11, 2026
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Shelby Ann Sampson
Grantham, US
★★★★★ 5
Small toe box BUT SOO cute
Size: 8.5, Color: Natural Snake
Very cute but if you have wide toes and typically require a wider toe box you’ll end up with blisters if you walk a lot in them.
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Reviewed in the United States on May 16, 2026
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KRYSTAL PETTUS
Port Orchard, US
★★★★★ 3
Cute but uncomfortable
Size: 6.5, Color: Black Leather
I’m usually a size 6. I got a 6.5, they fit perfect. Super cute, but just from trying them on and walking around my fit we’re already turned red. Still going to wear them to my event but I’m in for one lol
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Reviewed in the United States on November 23, 2025

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