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

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

by Mishimoto
Sale Sale
$122.34
$122.34 - $122.34
$122.34
$103.95
$103.95 - $103.95
$103.95
SKU MISMMTC-L5P-TBVFF

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+ 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 add even more heat dissipation. This 2017+ 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
2021 Chevrolet Silverado 2500 HD Custom
2017-2021 Chevrolet Silverado 2500 HD High Country
2017-2021 Chevrolet Silverado 2500 HD LT
2017-2021 Chevrolet Silverado 2500 HD LTZ
2017-2021 Chevrolet Silverado 2500 HD WT
2017-2021 Chevrolet Silverado 3500 HD High Country
2017-2021 Chevrolet Silverado 3500 HD LT
2017-2021 Chevrolet Silverado 3500 HD LTZ
2017-2021 Chevrolet Silverado 3500 HD WT
2020-2021 GMC Sierra 2500 HD AT4
2017-2021 GMC Sierra 2500 HD Base
2017-2021 GMC Sierra 2500 HD Denali
2017-2021 GMC Sierra 2500 HD SLE
2017-2021 GMC Sierra 2500 HD SLT
2020-2021 GMC Sierra 3500 HD AT4
2017-2021 GMC Sierra 3500 HD Base
2017-2021 GMC Sierra 3500 HD Denali
2017-2021 GMC Sierra 3500 HD SLE
2017-2021 GMC Sierra 3500 HD SLT
Shipping/Returns

The following are the terms and conditions that constitute our Shipping Policy.

Domestic Shipping Policy

Shipment processing time

All orders are processed within 1-2 business days. Orders are not shipped or delivered on weekends or holidays. If we are experiencing a high volume of orders, shipments may be delayed by a few days. Back order items are subject to special shipping times. If there will be a significant delay in shipment of your order, we will contact you via email or telephone.

Shipping rates & delivery estimates

Standard Shipping is 2-5 days.

We offer free ground shipping for orders over $200 within the United States.

Shipping charges for your order will be calculated and displayed at checkout.

*Overnight delivery is only available for orders with delivery addresses within the continental United States.

**Delivery delays can occasionally occur

Shipment to P.O. boxes or APO/FPO addresses

RAV Performance​ ships to addresses within the U.S., U.S. Territories, and APO/FPO/DPO addresses.

Shipment confirmation & Order tracking

You will receive a Shipment Confirmation email once your order has shipped containing your tracking number(s). The tracking number will be active within 24 hours.

Customs, Duties and Taxes

RAV Performance is not responsible for any customs and taxes applied to your order. All fees imposed during or after shipping are the responsibility of the customer (tariffs, taxes, etc.).

Damages

RAV Performance​ is not liable for any products damaged or lost during shipping. If you received your order damaged, please contact the shipment carrier to file a claim. Please save all packaging materials and damaged goods before filing a claim.

International Shipping Policy

We currently do offer international shipping within some countries. Please contact us by email or phone to place an order.