When performing transmission repairs on 2016-2019 Silverado and Sierra models and 2015-2020 Tahoe, Suburban and Yukon models equipped with the 6L80 6-speed automatic transmission (RPO MYC) for harsh shift, delayed shift, shudder, noise or vibration conditions, also replace the Thermal Bypass Valve (TBV). (Fig. 8)
Fig. 8
A new TBV is available that has a cooler operating temperature. The previous TBV had a full-open temperature of 194°F (90°C). The new TBV has a full-open temperature of 158°F (70°C).
The new TBV can be identified by the “70” stamped into the bottom of the valve. (Fig. 9) The “70” stamp is visible on the valve when it is installed on the transmission.
Fig. 9
The TBV should be replaced with the new valve only once for any transmission repairs, including Customer Concern Not Duplicated (CCND). The TBV should not be replaced again unless it is determined through normal diagnosis that the TBV has failed.
TIP: If vehicle is equipped with a new TBV, the transmission fluid level should be checked only after the transmission fluid temperature (TFT) has reached or exceeded an operating temperature of 158°F (70°C). Reaching or exceeding an operating temperature of 158°F (70°C) opens the bypass valve and allows the cooler to fill up with fluid, which will result in a more accurate fluid level check.
Refer to Bulletin #21-NA-199 for additional information and part numbers.
– Thanks to Mark Gordon
Updated October 16, 2021
Is Part # 13511136 the old 194* thermal bypass valve? Or is it a new number for part # 86774933?
Is a reprogram needed after install?
New TBV – 86774933
For MY 2014-2015 vehicles with quick connect transmission cooler lines, the cooler lines will need to be replaced as well. See the EPC.
Is there a part number for this new TBV?
Bulletin #21-NA-199: Information on Installation of a New Thermal Bypass Valve (TBV) – (Oct 6, 2021) is now available.
As of 10.06.2021 Bulletin #21-NA-199 does not exist