6L80 6L90 8L90 10L80 10L90 10L000 Equipped Vehicles With A Harsh Shift Shudder Surge Stall Or High Transmission Fluid Temperature – 2021-2023 Cadillac Chevrolet GMC

NHTSA ID Number: 10222668

Manufacturer Communication Number: 22-NA-182

Summary

This informational bulletin advises the tech to check if the trans cooler lines are twisted which may cause the customers concern.

 


Condition

Some customers may comment on one or more of the following before or after the transmission has been overhauled:

  • Harsh shifting
  • Shudder
  • Surging
  • Stalling
  • Transmission overheating

Some customers may also comment on above normal transmission fluid temperature.

 

Cause

This condition may be caused by a twisted cooler line on low mileage vehicles.

Note: A twisted cooler line may cause DTC P27EC to set in the TCM on ETRS transmissions. (RPO MHS MQC).

Inspect for a twisted cooler line, example shown in the graphic above.

In some cases, it may be necessary to remove the under body panels in order to clearly see the cooler lines.

  • If the cooler line is twisted, disconnect the cooler line from the transmission auxiliary cooler and untwist it, then reconnect the cooler line.
  • If the cooler line remains misshaped after untwisting, the cooler line should be replaced then check the transmission fluid level following SI. Add fluid if needed.
  • If no concerns are found with the rubber line being misshaped, check the transmission fluid level following SI. Add fluid if needed.

The Thermal Bypass Valve (TBV) may be the cause of the overheat if a cooler line is not twisted or misshaped. The TBV will open at the following temperatures for the models listed in this TSB. 6 Speed (6L80, 6L90) – 158F (70C) – TBV is external to the transmission 8 Speed (8L90) – 194F (90C) – TBV is external to the transmission 10 Speed (10L80, 10L90, 10L1000) – 143F (61C) – TBV is within the valve body on all listed applications expect those equipped with 3.0 (LM2) Diesel. On the LM2 Diesel the TBV is external to the transmission

 


32 Affected Products

Vehicles

MAKEMODELYEAR
CADILLACESCALADE2021-2023
CHEVROLETSILVERADO 15002021-2023
CHEVROLETSILVERADO 25002021-2023
CHEVROLETSILVERADO 35002021-2023
CHEVROLETSUBURBAN2021-2023
CHEVROLETSUBURBAN 15002021-2022
CHEVROLETTAHOE2021-2023
GMCSIERRA 15002021-2023
GMCSIERRA 25002021-2023
GMCSIERRA 35002021-2023
GMCYUKON2021-2023

 


1 Associated Document

Manufacturer Communications

Bulletin No.: 22-NA-182
Date: September, 2022

MC-10222668-0001.pdf 62.012KB

 


NHTSA ID Number: 10217793

Manufacturer Communication Number: PIP5792E

Summary

This Preliminary information communicates to the dealer technician that if a customer comments that their vehicle equipped with a 6L80, 6L90, 8L90, 10L80, or 10L100 transmission has a harsh shift, shudder, stall or high transmission fluid temperature concern they should inspect for a twisted transmission cooler line. Technicians are instructed to disconnect the cooler line and untwist it then reconnect the cooler line and inspect the cooler line for being misshaped. Technicians are instructed to replace the cooler line if it is misshaped.

 

1 Associated Document

Manufacturer Communications

Bulletin No.: PIP5792E
Published date: 07/29/2022

MC-10217793-9999.pdf 197.713KB

 


 

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