Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to 2019 and prior GM passenger cars and light duty trucks with automatic transmission.

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  Models: 2019 and Prior GM Passenger Cars and Light Duty Trucks with Automatic Transmission

• Water or ethylene glycol in the ATF changes clutch friction and often causes 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. Signs of water include ATF blowing out of the vent tube and ATF that looks cloudy or, when heavily contaminated, like a strawberry milkshake.

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   ATF blowing out of the transmission vent tube. • ATF may appear cloudy or, in cases of extreme contamination, have the appearance of a strawberry milkshake.

2. Other signs: visible water in the oil pan, a milky white substance inside the pan area, and spacer plate gaskets that appear glued to the valve body face or case.

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   Visible water in the oil pan. • A milky white substance inside the pan area. • Spacer plate gaskets that appear to be glued to the valve body face or case.

3. If the water source is not identified, or a leaking in-radiator transmission oil cooler is suspected, a test kit is available that detects ethylene glycol in ATF.

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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.

4. Test the ATF with the "Gly-Tek" kit from the Nelco Company 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 and all composition-faced clutch plates and/or bands must be replaced.

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   Important: If water or coolant is found in the transmission, the following components MUST be replaced. • Replace all of the rubber-type seals. • Replace all of the composition-faced clutch plates and/or bands.

2. Also replace all nylon parts and the torque converter, and thoroughly clean and rebuild the transmission with new gaskets and oil filter.

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   Replace all of the nylon parts. • Replace the torque converter. • Thoroughly clean and rebuild the transmission, using new gaskets and oil filter.

3. When repairing or replacing, 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 or repair as necessary.

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