SKU: 48526865078

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

Sale price$89.95 Regular price$99.95
Save 10%

Pay in installments of $24.99 with ShopPay, AfterPay and Klarna

Shipping Estimate
USA
  • USA
  • CAN

Ships within 48 hours · Estimated delivery Jul 20 - Jul 25

Promo Codes Available:

For Your Every Summer RSVP, with Code: SUMMER15

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.

This Part Fits:

Year Make Model Submodel
2017-2019 Chevrolet Silverado 2500 HD High Country
2017-2019 Chevrolet Silverado 2500 HD LT
2017-2019 Chevrolet Silverado 2500 HD LTZ
2017-2019 Chevrolet Silverado 2500 HD WT
2017-2019 Chevrolet Silverado 3500 HD High Country
2017-2019 Chevrolet Silverado 3500 HD LT
2017-2019 Chevrolet Silverado 3500 HD LTZ
2017-2019 Chevrolet Silverado 3500 HD WT
2017-2019 GMC Sierra 2500 HD Base
2017-2019 GMC Sierra 2500 HD Denali
2017-2019 GMC Sierra 2500 HD SLE
2017-2019 GMC Sierra 2500 HD SLT
2017-2019 GMC Sierra 3500 HD Base
2017-2019 GMC Sierra 3500 HD Denali
2017-2019 GMC Sierra 3500 HD SLE
2017-2019 GMC Sierra 3500 HD SLT
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: 48526865078

Discover Niche Categories That Outsell

Top-Converting Item to Boost Your Average Order

4.8 ★★★★★
Based on 29 reviews
Sort
Highest Rating
Newest First
Oldest First
Product Reviews
T
Verified Purchase
TJ Smith
Lowell, US
★★★★★ 5
👍🏻
Color: Dark Grey Heather, Size: X-Large
Comfy sized right
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 29, 2026
B
Verified Purchase
beverly s
Fort Morgan, US
★★★★★ 4
NICE FOR THE PRICE
Color: Dark Grey Heather, Size: X-Large
Nice for the price. Runs true to size. Lightweight
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on November 17, 2025
W
Verified Purchase
Wess F. Kroll
Belleville, US
★★★★★ 5
Long live Maelreg
Color: Black Grey Heather, Size: Medium
Most comfortable hoodie I own. Perfect for on the course or hitting the gym
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 1, 2026
K
Verified Purchase
k_raya11
Omaha, US
★★★★★ 5
Everyday wear!
Color: Dark Grey Heather, Size: X-Large
Great purchase! Stylish on those not so cold days. Fits true the size and the material is very soft! I want to buy a few more of these in different colors.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on November 11, 2025
T
Verified Purchase
Tina Pessina
Los Angeles, US
★★★★★ 5
He liked it
Color: Turquoise Heather, Size: Medium
He liked it so that’s good- rice is good for item
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 10, 2026

recommand products