Allison LTC1000 Discolored Transmission Fluid With No Loss In Performance - keywords condition contaminated

This PI is being superseded to include more model years. Please discard PIP3254.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Chevrolet Silverado and GMC Sierra trucks equipped with the Allison LCT1000 Automatic Transmission may experience a condition in the which the transmission fluid has become dark/discolored (dark brown to black). There will not be any transmission performance issues with the transmission.

Testing performed by Allison Transmission indicates that this symptom shows a degree of viscosity breakdown of the Automatic Transmission Fluid (ATF). Viscosity breakdown occurs with vehicle usage and occurs more rapidly with increased loads and heat. If this condition is encountered the ATF and external spin-on ATF filter should be replaced and the transmission oil cooler lines and coolers should be flushed.

Additional trucks used for towing or hauling should utilize the Tow/Haul Mode when the Gross Combined Weight is 75% of the vehicles Gross Combined Weight Rating.

The use of synthetic automatic transmission fluid though not a requirement can be used if requested by the customer. Allison Transmission does market a synthetic fluid called TranSynd and it is available through GMSPO under part number 12378515 in the US and 88900701 in Canada. The fluid is a ship direct part and is available in cases of 12 quarts.

The following is a summary of the owners manual recommended maintenance schedule for the ATF and spin-on filter.

2004-2007: Spin-on filter (external filter) only at first maintenance service performed on the vehicle, Normal Service; ATF and spin-on filter every 50,000 miles, Severe Service; ATF & spin-on filter every 25,000 miles

2003: Spin-on filter at first 7,500 miles, Normal Service; ATF & spin-on filter every 50,000 miles, Severe Service; ATF and spin-on filter every 25,000 miles

2002: Normal Service; ATF and spin-on filter every 50,000 miles, Severe Service; ATF and spin-on filter every 25,000 miles

2001: Normal Service; ATF and spin-on filter every 50,000 miles, Severe Service; ATF and spin-on filter every 25,000 miles

Owners Manual Severe Service Guideline: If the vehicle is mainly driven under one or more of the following conditions;

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.