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

Mishimoto
MISMMTC-L5P-TBVFF
In stock
Transmission Coolers
$131.00 $118.95
The Allison transmission is the backbone of your L5P Duramax. It's responsible for transmitting large quantities...
$118.95
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Mishimoto 2017+ GMC 6.6L Duramax L5P Transmission Thermal Bypass Valve Kit
Description
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
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Effective Date: October 2024
We offer a 30-day return policy, allowing you to request a return within 30 days of receiving your item. To qualify for a return, the item must be in its original condition—unused, with tags, and in its original packaging. A receipt or proof of purchase is also required.

To initiate a return, please contact us at info@riotparts.com. Returns must be shipped to the address provided upon request. If your return is approved, we will issue a return shipping label along with detailed instructions.

Important
Returns sent without prior authorization will not be accepted.

For any return-related inquiries, please reach out to us at info@riotparts.com.

Return Shipping Address
The return shipping address will be determined based on the requestor’s location to ensure the nearest return facility is used.

Possible return locations include:
• 10880 Lear Blvd.
Reno, NV 89506, United States
• 931 W. Bardin Rd., Suite 150–200
Arlington, TX 76017, United States
• 3035 Campus Dr.
Hatfield, PA 19440, United States
• 5789 N. Graham Road, Ste 200
Whiteland, IN 46184, United States
• 2020 NE Aloclek Dr 4711 N Lamon Ave
#118 STE 12, Hillsboro, OR 97124, United States

Damages and Issues
We recommend inspecting your order upon receipt. If you find that an item is defective, damaged, or if you received the wrong item, please contact us immediately so we can address the issue.

Exceptions / Non-Returnable Items
Certain items cannot be returned, including:
• Electrical parts that have been installed or used
• Special order parts that were custom ordered for you
• Items that have been damaged due to improper installation or use

If you have questions or concerns about a specific item, please contact us for assistance.

Exchanges
For exchanges, the quickest option is to return the item you have. Once the return is accepted, you can make a separate purchase for the new item.

Refunds
We will notify you once we receive and inspect your return to inform you whether your refund is approved. If approved, you will be automatically refunded using your original payment method within 10 business days. Please be aware that it may take additional time for your bank or credit card company to process and post the refund.

If more than 15 business days have passed since your return was approved and you haven’t received your refund, please contact us at info@riotparts.com.

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