SKU: 73309385794

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

Sale price$89.99 Regular price$99.99
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  • USA
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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 2017-2019 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.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
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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: 73309385794

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4.4 ★★★★★
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tjw
Los Angeles, US
★★★★★ 3
Way too narrow
Size: 9.5 Wide, Color: Burgundy Polished Full Grain
I ordered a wide in this shoe, but it was still way too narrow. I had to return them. Otherwise, it looked like a nice quality shoe.
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Reviewed in the United States on February 12, 2026
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BetterEveryDay
Bozeman, US
★★★★★ 5
I usually wear 11.5's, but I buy 1/2 size smaller to accommodate for stretch. Leather relaxes.
Size: 11, Color: Burgundy Polished Full Grain
5 STARS: These shoes are awesome. I keep coming back for more. I have major foot problems, have tried all kinds of shoes, orthotics, and inserts... but believe it or not, these shoes work better than any of that stuff. I wear them daily. I buy lots of them, for home, for church, and I'm getting my first pair of J&M boots today, for winters in Indiana... Brrrr
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Reviewed in the United States on December 18, 2025
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Doc
Chelsea, US
★★★★★ 5
Great price great shoe
Size: 12, Color: Burgundy Polished Full Grain
Excellent shoe. Tried the Sebago penny loafer and the sizing was ridiculous. These J and M are sized perfectly. I’ve had them before and they wear like iron. Very comfortable right out of the box.
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Reviewed in the United States on May 23, 2026
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roger mendes
Carnegie, US
★★★★★ 5
One of the best shoes
Size: 9.5, Color: Black Polished Full Grain
Outstanding. Fashionable, most comfortable and good construction. No sines of use after quite some time. Highly recommended.
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Reviewed in the United States on March 21, 2026
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xyz
Belleville, US
★★★★★ 4
Quality shoe but with a slight squeak.
Size: 10 Wide, Color: Burgundy Polished Full Grain
Nice shoes with the classic Penny Loafer design. Fit was better than another brand I tried. Only reason not 5 starts is disappointment due to a slight squeak at times when walking.
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Reviewed in the United States on August 11, 2025

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