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Ships within 48 hours · Estimated delivery Jul 6 - Jul 11
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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:
- 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
4.4 ★★★★★
Based on 1248 reviews
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Product Reviews
★★★★★ 1
Disappointed
Color: Gray, Size: Queen (2 Count)
Not cooling and bad fit.
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Reviewed in the United States on August 26, 2025
★★★★★ 5
They work!
Color: Gray, Size: Queen (2 Count)
They do keep my pillow cool!
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Reviewed in the United States on September 8, 2025
★★★★★ 4
Interesting pillowcase that does run cool to the touch
To begin: I'm a 64 y/o woman who still gets hot flashes, despite air-conditioning and a fan blowing on me at night. It's the sheets off then blankets on routine that so many of us know. I ordered this pillowcase hoping that I would find some kind of relief in the night, even it was only for my head.
The fabric is very unusual. It's a silky nylon blend, very swishy and soft. It reminds me of luxury, expensive women's lingerie. It's extremely slippery, moreso when you have your head on it; there certainly won't be any resistance or pulling on the hair all night.
I washed it before using it, put it in a mesh bag to protect it from getting snagged. It washed and dried as good as new. One thing to note: because it is so slippery the pillow may want to slide a little out of the pillowcase.
I slept quite well and did not experience any heat or sweating on it.
The reason for the 4* and not 5* is the price, at almost $20 it is a bit pricey for a rectangle of nylon fabric. I could see if it were real silk, but it's not. Otherwise it's exactly what it purports to be.
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Reviewed in the United States on July 29, 2025
★★★★★ 5
The perfect cooling pillows!!
Photo taken after about half of the filling was removed and many months of use. Still my favorite pillows ever!
I absolutely love these adjustable cooling pillows! They keep me cool all night long (must use without a pillowcase for cooling effect.)
They arrived with enough filling to make them super firm and extremely thick. They took several hours to fully puff up. I removed about half the filling to make a more plush pillow which I prefer and they’re still thick and comfy. They offer the perfect amount of support. I’m actually sleeping better!
Bonus: I saved the extra filling and used it to stuff throw pillow covers.
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Reviewed in the United States on March 13, 2026
★★★★★ 5
Comfy!
I did have to take some stuffing out for my comfort. After that it is amazing! Love that the pillow is cool!
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Reviewed in the United States on April 29, 2026