SKU: 79711077414

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

Sale price$133.19 Regular price$147.99
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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 thermal bypass valve upgrade for your 2017-2019 Chevrolet/GMC 6.6L Duramax. Our CNC-machined aluminum thermal bypass valve not only looks better than the stock unit, but it performs better too. This Mishimoto thermal bypass valve kit includes a fully serviceable thermostat for fast warm-up in cold climates. This kit also includes a thermostat bypass that can be installed to provide constant cooling in warm climates or for use in extreme driving/towing conditions. 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 Thermal Bypass Valve Kit is built to last a lifetime with a durable black anodized finish and our Mishimoto Lifetime Warranty.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
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]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 79711077414

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4.7 ★★★★★
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Katie
Belleville, US
★★★★★ 5
Nice and heavy
Size: Small, Color: Dark Green
Nice quality, heavyweight. My child wears this all the time, it’s really nice.
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Reviewed in the United States on May 24, 2026
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Ajai
Chelsea, US
★★★★★ 1
Size is wayyyyy off
Size: X-Large, Color: Black
Super small ain’t no way this is an X-Large
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Reviewed in the United States on May 7, 2026
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Rach
Lowell, US
★★★★★ 5
Love these!!!
Special Size: 7" Inseam without Pockets, Size: Large, Color: Ocean Blue
Super happy with these shorts!!! Wore them on a full day at the theme park. Stayed in place and did not ride up. No pinching or constricting. The material is buttery soft and the blue is so vibrant and pretty!! Don’t show every bump and imperfection, but does show some. It’s not totally smoothing. Very work out friendly, heat friendly, running errands friendly. Would definitely recommend and plan to buy other colors. Comfy waist band as well.
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Reviewed in the United States on May 11, 2026
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CLJ_WV
Battle Creek, US
★★★★★ 5
Excellent Work-out & Biking Short
Special Size: 7" Inseam without Pockets, Size: Small, Color: Ocean Blue
I love these biker shorts. They have just the right amount of lycra and they are super soft. They are true to size, and they fit perfectly on my 5'2", 125-pound frame. I purchased them for use in bike riding, and I am very pleased with the fit and stretch. The inseam length is perfect for bike riding, and the legs don't ride up my thigh. The only con to all the pros is there isn't a phone pocket. I ride my bike around town, and I would have liked to have a pocket for my phone when going inside a store. These shorts are well worth the price. I purchased three different colors and love them all. I would definitely purchase this item again.
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Reviewed in the United States on January 7, 2026
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Amanda
Charlottesville, US
★★★★★ 4
Cute but could use some pockets
Special Size: 6" Inseam Contrast Trim without Pockets, Size: Small, Color: Navy/White
Obsessed with these shorts. They are so cute and comfy. They fit true to size and I love that there is a matching top you can buy separately. I feel like the material is pretty thick and I don't have to worry about it being see through. My only complaint is that there are no pockets.
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Reviewed in the United States on June 2, 2026

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