Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to 2025 and prior GM passenger cars and trucks equipped with an automatic transmission.

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  2025 and Prior GM Passenger Cars and Trucks (including Chevrolet Medium Duty LCF Equipped with Gas Engine and 6L90 Transmission) Equipped with Automatic Transmission

• Water or ethylene glycol in ATF changes the friction of the clutches, frequently causing shudder during engagement or gear changes, especially during torque converter clutch engagement.

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  Water or ethylene glycol in ATF will also change the friction of the clutches, frequently resulting in shudder during engagement or gear changes, especially during torque converter clutch engagement.

Steps to confirm (in the document’s order)

1. An indication of water in the ATF: ATF blowing out of the transmission vent tube.

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   ATF blowing out of the transmission vent tube.

2. The ATF may appear cloudy or, with extreme contamination, look like a strawberry milkshake.

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   ATF may appear cloudy or, in cases of extreme contamination, have the appearance of a straw- berry milkshake.

3. There may be visible water in the oil pan or a milky white substance inside the pan area.

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   Visible water in the oil pan. • A milky white substance inside the pan area.

4. Spacer plate gaskets appear swollen or wrinkled in areas where they are not compressed.

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   Spacer plate gaskets that appear to be swollen or wrinkled in areas where they are not compressed.

5. If water is found in the ATF and its source is not identified, or a leaking in-radiator transmission oil cooler is suspected, a simple and quick test kit that detects ethylene glycol in ATF is available.

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   If water in the ATF has been found and the source of the water entry has not been identified, or if a leaking in-radiator transmission oil cooler is suspected (with no evidence of cross-contamination in the coolant recovery reservoir), a simple and quick test kit is available that detects the presence of ethylene glycol in ATF.

6. Obtain the Gly-Tek test kit from the Nelco Company and test the ATF to decide accurately whether the radiator needs to be replaced.

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   The “Gly-Tek” test kit, available from the Nelco Company, should be obtained and the ATF tested to make an accurate decision on the need for radiator replacement.

Repair

1. If water or coolant is found in the transmission, all rubber-type seals, all composition-faced clutch plates and/or bands, all nylon parts and the torque converter must be replaced.

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   If water or coolant is found in the trans- mission, the following components MUST be replaced. • Replace all of the rubber-type seals. • Replace all of the composition-faced clutch plates and/or bands. • Replace all of the nylon parts. • Replace the torque converter.

2. Thoroughly clean and rebuild the transmission, using new gaskets and oil filter.

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   Thoroughly clean and rebuild the transmission, using new gaskets and oil filter.

3. Flush and flow check the transmission oil cooler using J-45096.

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   Flush and flow check the transmission oil cooler using J-45096.

4. Thoroughly inspect the engine cooling system and hoses and clean/repair as necessary.

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   Thoroughly inspect the engine cooling system and hoses and clean/repair, as necessary.