Twisted Transmission Cooler Line

A harsh shift, shudder, surge or stall condition may be present on some 2021 Silverado, Tahoe, Suburban, Sierra, Yukon, and Escalade models equipped with the 6L80 or 6L90 6-speed automatic transmission (RPOs MYC, MYD), 8L90 8-speed automatic transmission (RPO MQE), or 10L80 or 10L1000 10-speed automatic transmission (RPOs MQC, MQB, MGM, MGU) and with low mileage. These conditions may be caused by a twisted transmission cooler line. (Fig. 11)


Fig. 11


When checking for a twisted cooler line, it may be necessary to remove the underbody panels in order to clearly see all the lines.

If a twisted cooler line is found, disconnect the cooler line from the transmission auxiliary cooler and untwist it. Reconnect the cooler line if the rubber is not deformed or misshapen or there are not any other issues with the line. If the cooler line is damaged or deformed from being twisted, it should be replaced.

Check the transmission fluid level following the procedures in the appropriate Service Information and add fluid if needed.


– Thanks to Terry Neuendorf

Latest EL-50332 EV Battery Service and Depowering Tool Software Released
Poor Heater Performance

Leave a Reply

Your email address will not be published. Required fields are marked *