Document ID: 6147440

Subject:

Information on 6L80 6L90 8L90 10L80 10L90 10L1000 Equipped Vehicles With A Harsh Shift, Shudder, Surge, Stall, Neutral/Flare, Transmission Overheating and/or High Transmission Fluid Temperature

This bulletin replaces PIP5792E. Please discard PIP5792E.

Brand:	Model:	Model Year:		VIN:		Engine:	Transmission:
Brand:	Model:	from	to	from	to	Engine:	Transmission:
Cadillac	Escalade	2021	2024			L87, LM2, LT4	MHS MHO MQC
Chevrolet	Silverado 1500	2021	2021			L84, L8Z, LM2	MHS, MHT, MQB MQC MQE MYC
	Silverado 1500 LTD (RPO J21, VIN Digit 5 = W / Y)	2022	2022			L84, L8Z, LM2	MHS MHT MQB MQC MQE MYC
	Silverado 1500 New (RPO J22, VIN Digit 5 = A / D)	2022	2022			L84, L8Z, LM2	MHS MHT MQB MQC MQE MYC
	Silverado 1500	2023	2024			L84 L87 LM2	MHS, MHT, MQB, MQC MQE MYC
	Silverado 2500HD 3500HD	2021				L5P, L8T	MKM, MGM, MGU, MYD
	Suburban	2021				L84, L87, LM2	MHS MQC
	Tahoe	2021				L84, L87, LM2	MHS MQC
GMC	Sierra 1500	2021	2021			L84, L8Z, LM2	MHS MHT MQB MQC MQE MYC
	Sierra 1500 Limited (RPO J21, VIN Digit 5 = 8 / 9)	2022	2022			L84, L87, LM2	MHS MHT MQB MQC MQE MYC
	Sierra 1500 New (RPO J22, VIN Digit 5 = H / U)	2022	2022			L84, L87, LM2	MHS MHT MQB MQC MQE MYC
	Sierra 1500	2022	2024			L84, L87, LM2	MHS, MHT, MQB, MQC, MQE, MYC
	Sierra 2500HD 3500HD	2021				L5P, L8T	MKM, MGM MGU MYD
	Yukon	2021				L84, L87, LM2	MHS MQC

Involved Region or Country	North America, Uzbekistan, Middle East, Brazil (Mercosur), Colombia (West), Ecuador (West), Peru (West), Japan, Cadillac Korea (South Korea), Thailand (ASEAN), Europe, Australia, New Zealand.
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 Neutral/Flare 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 except those equipped with 3.0 (LM2) Diesel. On the LM2 Diesel, the TBV is external to the transmission.

Important: Service agents must comply with all International, Federal, State, Provincial, and/or Local laws applicable to the activities it performs under this bulletin, including but not limited to handling, deploying, preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a conflict between the procedures set forth in this bulletin and the laws that apply to your dealership, you must follow those applicable laws.

Version

Modified

Released September 06, 2022

Revised December 19, 2022 - Added Neutral/Flare to Subject and Condition section.

Revised August 15, 2023 - Added 2024 Model Year and RPO MKM to Heavy Duty Transmission section.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

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