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

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

Marsoni

M251S

$108.93

Get it in 3 business days with 1 day shipping. Friday, May 29

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

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Good product, not much to say. The product arrived quickly, looks to be of high quality construction, fit perfectly and took me only a couple of minutes to install. I love it when a product is no frills and delivers as advertised. I've used various filters from K&N before and have always had very good success with them so I will be buying more of these for sure when the time comes.

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Reviewed in the United States on November 9, 2025

Verified Purchase

john A.

Omaha, US

★★★★★ 5

Better than most.

Size: (Pack of 1)

Looks good, perfect fit.

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Reviewed in the United States on May 25, 2026

Verified Purchase

Willy Bill

West Palm Beach, US

★★★★★ 5

Great Filter

Size: (Pack of 1)

This fits fine. Just wish it was a little easier to change.

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Reviewed in the United States on April 26, 2026

Verified Purchase

Los Angeles, US

★★★★★ 5

More power, slightly lower (8%) MPG.

Size: (Pack of 1)

Installed on a 2.0 liter Subaru Impreza. I drive up/down the I5 in california 3-4 times a year. For those that don't know there is about a 200 mile flat stretch where everyone runs at 75-85mph. With various filters (FRAM, BOSCH, Subaru OEM), I would consistently get 29.8 mpg. Once I installed the K&N, I could feel the car pulling with a bit more power, but I noticed that I was getting about 27.5 mpg. Totally worth it as the impreza is a little under powered and I don't drive many miles (6k/year) but if you are putting a lot of miles on your car, you may want to have more mpg.

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Reviewed in the United States on May 24, 2026

Verified Purchase

GregUPerkio

Battle Creek, US

★★★★★ 5

fits my 2013 chevy suburban 5.3 and appears to be high quality

Size: (Pack of 1)

fits my 2013 suburban perfectly. looks to be a well constructed unit.

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Reviewed in the United States on March 29, 2026