Symptoms - Automatic Transmission. GMC Truck Sierra

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2008 🢒 Sierra - 4WD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - Allison 🢒 Symptoms - Automatic Transmission

The following table consists of six diagnostic categories that are located in the left-hand column. Using this column, choose the appropriate category based on the operating conditions of the vehicle or transmission. After selecting a category, use the right-hand column to locate the specific symptom diagnostic information.

Diagnostic Category

Diagnostic Information

Important: The Functional Test Procedure should be performed before beginning any diagnosis. If this procedure has not already been performed, refer to Functional Test .

Fluid Diagnosis

This category contains the following topics:

•	Fluid condition - appearance, contaminants, smell, overheating

•	Line pressure - high or low

•	Low lubrication pressure

•	Fluid leaks

•	Refer to Transmission Fluid Check .

•	Refer to Transmission Overheats .

•	Refer to Low Main Line Pressure in All Ranges .

•	Refer to Low Main Line Pressure in Specific Ranges, Normal Pressure in Other Ranges .

•	Refer to Low Lubrication Pressure .

•	Refer to Fluid Leak Diagnosis .

•	Refer to Fluid Leaks from Fluid Fill Tube and/or Vent .

•	Refer to Fluid Leaks from Transmission Input .

•	Refer to Fluid Leaks from Transmission Output .

•	Refer to Contaminated Transmission Fluid .

•	Refer to Intermittent Buzzing Noise .

Noise and Vibration Diagnosis

This category contains the following topics:

•	Noise - drive gear, final drive, whine, growl, rattle, buzz, popping

•

Vibration

•	Refer to Noise and Vibration Analysis .

•	Refer to Flex Plate/Torque Converter Vibration Test .

Range Performance Diagnosis

This category contains the following topics:

•	Drives in Neutral

•	Excessive creep

•	Will not shift to Forward or Reverse

•	Will not stay in Forward or Reverse

•	Will not make a specific shift

•	Refer to Abnormal Activities or Responses .

•	Refer to Transmission Will Not Shift to Forward or Reverse .

•	Refer to Transmission Will Not Stay in Forward or Reverse .

•	Refer to Transmission Will Not Make a Specific Shift .

Shift Quality - Feel Diagnosis

This category contains the following topics:

•	Erratic shifts

•	Harsh, soft, delayed or slipping shifts

•	Harsh, soft, or delayed engagement

•	Refer to Transmission Does Not Shift Properly .

•	Refer to Excessive Slippage and Clutch Chatter .

•	Refer to Excessive Flare - Engine Overspeed on Wide-Open Throttle .

Shift Speed Diagnosis

This category contains the following topic:

Inaccurate or inconsistent shift points

Refer to Transmission Does Not Shift Properly .

Torque Converter Diagnosis

This category contains the following topics:

•	Poor performance

•	Noise during converter operation

•	TCC shudder

•	Shudder after TCC apply

•	Vibration during converter operation

•	Refer to Torque Converter Diagnosis .

•	Refer to Flex Plate/Torque Converter Vibration Test .