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XD396 XDP X-Tra Cool Transmission Cooler Thermostatic Bypass - GMC/Chevy 6.6L Duramax 2017-2019

SKU: XD396
Mftr. Part#: XD396
The XDP X-Tra Cool Transmission Cooler Thermostatic Bypass helps lower temperatures and prolong the life of your Allison transmission in your 2017-2019 GMC/Chevy 6.6L Duramax.

PRODUCT SPECS (click to expand)

Attribute nameAttribute value
Truck Type/ModelDuramax
Product TypeThermal Bypass Valve (TBV)
BrandXDP (Xtreme Diesel Performance)


The factory bypass valve is designed in a way that restricts flow and when the thermostat fails it causes the fluid to bypass the transmission cooler completely resulting in elevated temperatures, premature transmission wear and in some cases even early transmission failure. The XDP thermostat bypass is a completely re-designed bypass block made from 6061 billet aluminum, this bypass valve removes the factory thermostat and allows for unrestricted flow to the transmission cooler at all times. The unrestricted flow can provide up to a 50 degree drop in transmission fluid temperature resulting in better cooling, less wear & tear and in many cases extends transmission life.


  • Direct fit replacement
  • No cutting of factory lines
  • Easily installs with hand tools
  • Helps improve transmission life
  • Eliminates┬áhot fluid recirculation
  • Lowers transmission fluid temp up to 50 degrees