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 thermal bypass valve upgrade for your 2017+ Chevrolet/GMC 6.6L Duramax. Our CNC-machined aluminum thermal bypass valve not only looks better than the stock unit, but it performs better too. This Mishimoto thermal bypass valve kit includes a fully serviceable thermostat for fast warm-up in cold climates. This kit also includes a thermostat bypass that can be installed to provide constant cooling in warm climates or for use in extreme driving/towing conditions. 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 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 POLICY

For US customers, we offer 3 shipping options:

• Free shipping for orders over $69. This shipping option takes 5-8 business days.
• Economy for small orders (less than 1lbs) $6.99
• This shipping option takes 5-8 business days. 
• Standard shipping (FedEx / UPS) for all orders $9.99 
• This shipping option takes 1-5 business days. 

*Most Arrow exhausts  ship directly from Italian warehouse!

It typically arrives at our store within 1-2 weeks, and then we'll ship it out to you right away!

*Most of M4 and Empire exhausts Due to high volume of sales, lead time could be up to 5-20 business days before shipping.

We are currently unable to offer   overnight or 2-day guaranteed shipping .

This is because the warehouses of most of our suppliers only ship Ground.

Products ship from our Miami facility or drop ship direct from our Suppliers

Orders placed before 11am CST are typically will send the same day. 

Most orders placed after that time are will send the following business days. 

 

If you have specific shipping requests or needs please contact us at sales@bills-exhausts.com prior to purchasing and we will do our best to assist you.

If an item is back ordered from the manufacturer you will be notified by us. FYI – We don’t like it when this happens any more than you do.

We will try and help as best we can with back orders

A TRACKING NUMBER will be send to you via email or text after purchasing .

 

SHIPMENTS WITHIN THE U.S.

FREE STANDARD SHIPPING  on orders over $69 is available in all US lower 48 states, APO addresses, and Puerto Rico via USPS or UPS.  (*Exceptions apply for Alaska and Hawaii.)

Free standard shipping means we will select an option that gets you your parts as soon as possible while still being economically priced.

We reserve the right to deny free shipping for any reason.

About pre-orders:

When you order  PRE-ORDER it  means that you can purchase it before the official release date and then, you just wait for the shipping Usually pre-orders takes from 1-6 weeks depending the brand and the product. 

 

Contact us when ordering or we will contact you to go over rates and times.

INTERNATIONAL SHIPMENTS

WE SHIP WORLDWIDE Shipping rates outside the US are based upon destination and weight. 

Canada ,European Union and Puerto Rico Fast shipping with DHL Prepaid Customs/Taxes (DDP)

• * Countries we don't collect  tax or duties required pay by you.

Please note that we are unable to ship oversized items such as tires, batteries, and oils internationally.

For these items, we offer Large Truck Load (LTL) freight shipping.

Please be aware that LTL shipping costs may vary and exceed the estimated amount at checkout.

We will contact you for confirmation before processing your order.

If you have questions about these fees or duties contact us prior to ordering and we can assist you.

 -For international orders, customers who refuse the package will not receive a refund for the original shipping cost. Additionally, any return shipping fees incurred by us will be deducted from the customer's refund

 -Tires are not eligible for return.

 -Electronics are not eligible for return.

More for Return policy here

 

Delivery times for international shipments are typically 5 to 9 business days, but this can vary depending on your country’s customs procedures.

Orders delayed by customs are not something we can control or change.

 

ALL international orders (Includes CANADA ,California and Puerto Rico) needed to be ship from our location in Miami Florida.

Most of International orders cannot drop ship from supplier's warehouses(Except on some specific Brands)

Parts typically take 2-7 business days to arrive at our warehouse.

Once they're in, we'll send you a tracking number.

The estimated delivery time shown at checkout begins once the part is shipped from our warehouse