Sierra 2500 4WD V8-6.0L (2008)
Fluid Inspection
Important: Transmission fluid must be changed whenever there is evidence of dirt or a high temperature condition. High temperature
causes the transmission fluid to be discolored or to have a strong odor. Local conditions, severity of operation, or duty cycle may require
more or less frequent fluid or filter change intervals.
1. Examine the drained fluid for evidence of dirt.
Important: Cooler water may be contaminated by engine oil if an engine oil cooler is present; be sure to locate the correct source of
cooler water contamination.
2. Examine the drained fluid for evidence of water. Obvious water contamination of the transmission fluid or transmission fluid in the cooling water
from the heat exchanger indicates a leak between the water and fluid areas of the cooler. Inspect and pressure test the cooler to confirm the leak.
Replace leaking coolers.
Notice: Engine coolant in the transmission hydraulic system requires immediate action. Failure to clean or replace all contaminated components
may result in premature transmission failure.
3. Examine the drained fluid for evidence of engine coolant.
4. Examine the drained fluid for evidence of metal. Metal particles in the fluid, other than minute particles normally trapped in the oil filter, indicate
internal transmission damage. When this occurs, inspect the inside of the oil pan for excessive metal particles. Refer to Oil Pan Replacement (See:
Fluid Pan/Service and Repair/Allison - Automatic Transmission) .
5. Metal contamination requires complete transmission disassembly.
Notice: Flush the transmission cooling system and inspect for restrictions following a transmission failure. Failure to repair or replace restricted
oil cooling system components may result in premature transmission failure.
6. Clean all internal and external hydraulic circuits, cooler, and all other areas where the particles could lodge. Refer to Transmission Fluid Cooler
Flushing and Flow Test (See: Testing and Inspection/Component Tests and General Diagnostics/Allison - Automatic Transmission/Transmission
Fluid Cooler Flushing and Flow Test) .
