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2017-2019 L5P Duramax Transmission Cooler Thermostat Bypass Plug

- CNC Machined Billet Aluminum Thermostatic Bypass Plug
- Black Anodized Finish
- High temperature silicone O-ring seals
- Reduces fluid flow restriction to trans cooler
- Simple Installation
- Experience fluid temperature drops from 15-50 degrees F
- Direct replacement of the failure prone OEM thermostat
- Easy swap back to OEM setup for cold weather use
Pricing: $55.00



The stock thermostatic bypass for warming up the Allison quickly in cold weather conditions is a good idea in principle, but in practice we've seen the valve fail forcing trans fluid around the cooler in warm weather conditions that cause dangerous fluid temperatures for built and stock transmissions alike. We've been running this design on our shop development trucks and with our built transmissions successfully and are now making them available for purchase separately due to popular demand.

Recommended for trucks with stock or built transmissions and performing heavy towing in warm climates to help keep fluid temperatures in check.

The WCFab Transmission Cooler Thermostat Bypass Plug is a quick and easy install and will work with the following range of GM vehicles equipped with a factory installed transmission cooler thermostat bypass:

  • 2017-2019 Chevrolet Silverado & GMC Sierra 2500HD/3500HD with 6.6L Duramax Diesel
  • 2014-2018 Chevrolet Silverado & GMC Sierra 1500 with 4.3L 6 Cyl, 5.3L 8 Cyl, and 6.2L 8 Cyl Gas Engines
  • 2015-2020 Chevrolet Suburban, Tahoe & GMC Yukon with 5.3L 8 Cyl, and 6.2L 8 Cyl Gas Engines
  • 2015 Cadillac Escalade with 6.2L 8 Cyl Gas Engine



Shipping Information

  • Item Requires Shipping
  • 1.0 lbs.
  • W4.0000” x H4.0000” x L5.0000”
  • This item ships in its own box.

Customer Reviews

Comment Total Reviews (2)

Keep trans life extended for cheap
  • Currently 5/5 Stars

Reviewed by: Matthew10/07/2020 02:11PM

Product ownership: Less than 1 month

Purchased from: Wehrli Custom Fabrication - WCFab

Cheap and easy Purchase for my 2019 lp5 gmc denali easy install took about 30 mins dropped my trans temp at least 20 to 30 degrees usually ran 190 degrees now 135 to 150

Works just as advertised
  • Currently 5/5 Stars

Reviewed by: Joe01/24/2021 01:44AM

Product ownership: Less than 1 week

Purchased from: Wehrli Custom Fabrication - WCFab

I have a 2018 l5p and it was a easy install. Trans temp ran 150 degrees with outside temp of 45 degrees before install. After install I saw 105 degrees with the same outside temp.

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