Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to 2020 and prior GM passenger cars and trucks.

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  2020 and Prior GM Passenger Cars and Trucks

• Analyses of returned parts that were exposed to aftermarket "flushes" show indications of potential damage and shortened durability.

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  analyses of returned parts that have been exposed to these aftermarket “flushes” show indications of potential damage and shortened durability.

Possible causes

• Some aftermarket crankcase flushing materials are incompatible with GM engine components and can damage some engine seals and bearings.

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  Analysis of some of the aftermarket materials used for crankcase flushing indicate incompatibility with GM engine components and the potential for damage to some engine seals and bearings.

Repair

1. Flushing of A/C lines, radiators, transmission coolers and power steering systems is a recognized practice after catastrophic failures, or for extreme corrosion in radiators.

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   Flushing of air conditioning (A/C) lines, radiators, transmission coolers, and power steering systems are recognized practices to be performed after catastrophic failures or extreme corrosion when encountered in radiators.

2. Replace transmission fluid only by draining and refilling, following the procedures in Service Information (SI).

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   Transmission fluid should only be replaced by draining and refilling following procedures in Service Information (SI).

Caution

• GM does not endorse or recommend engine crankcase flushing for any of its gasoline engines.

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  General Motors Corporation does not endorse or recommend engine crankcase flushing for any of its gasoline engines.

• Engine damage resulting from crankcase flushing is not covered under the New Vehicle Warranty.

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  Damage to engine components resulting from crankcase flushing IS NOT COVERED under the terms of the New Vehicle Warranty.

• Subsystem flushing is not required or recommended for normal service operations.

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  This practice is not required or recommended for normal service operations.

• External transmission fluid exchange or flush machines are not recommended for the automatic or manual transmission; they may affect its operation or durability.

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  The use of external transmission fluid exchange or flush machines is not recommended for the automatic or manual transmission. Use of external machines to replace the fluid may affect the operation or durability of the transmission.