GM Service Manual Online
For 1990-2009 cars only

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The transmission fluid checking procedure is an important part of any mechanical/hydraulic system diagnosis. The transmission fluid condition can be a reliable indicator of the presence of problems within the transmission.

1

Did you perform the Powertrain or Transmission On-Board Diagnostic (OBD) System Check ?

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Go to Step 2

Go to Diagnostic Starting Point - Automatic Transmission

2

  1. Warm the transmission to the operating temperature by driving the vehicle the specified distance, or by running the engine until the Transmission Fluid Temperature has reached the value specified.
  2. Raise the vehicle on a hoist. The vehicle must be level when removing the transmission fluid fill plug. If a hoist is unavailable, the vehicle must be lifted at both ends and suitably supported.
  3. Caution: The engine must be running when the transmission fluid fill plug is removed, or excessive fluid loss will occur. Transmission fluid may be hot. Since the actual fluid level is unknown, stand clear when removing the fill plug. Have a container ready to capture any lost fluid. Do not turn the engine off with the fill plug removed, as you can be injured by hot transmission fluid being expelled out of the oil fill opening.

  4. Start the engine.
  5. With the engine running and the transmission at the normal operating temperature, remove the transmission fluid fill plug.
  6. Check the fluid color. If necessary, use a small screwdriver as a dip stick.

Important: The transmission fluid may darken with normal use and does not always indicate contamination or oxidation.

Is the fluid color clear red or light brown with no burnt odor?

15 miles (24 km) 113-185°F (45-85°C)

Go to Step 5

Go to Step 3

3

Does the fluid have a burnt odor or a dark brown color?

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Go to Step 8

Go to Step 4

4

Does the fluid have a cloudy or milky appearance?

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Go to Step 7

Go to Step 8

5

Check the fluid level. The fluid level should be even with the bottom of the threaded opening in the transmission oil pan.

Is the fluid level low?

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Go to Step 6

Go to Road Test

6

  1. With the engine running, add only enough DEXRON®-III Automatic Transmission Fluid to bring the fluid level to the bottom of the threaded opening in the transmission oil pan.
  2. Check the transmission for any external leaks in the following areas:
  3. • The transmission oil pans and gaskets
    • The transmission oil cooler lines
    • Refer to Fluid Leak Diagnosis .

Is the repair complete?

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Go to Road Test

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7

Replace the transmission oil cooler.

Is the repair complete?

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Go to Step 9

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8

Important: A very small amount of material in the bottom of the oil pan is a normal condition.

Drain the fluid. Check the bottom of the pan for any excessive debris.

Was a problem found?

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Go to Step 9

Go to Step 10

9

  1. Repair / Replace the transmission if required.
  2. Flush transmission oil cooler and lines.
  3. Add enough DEXRON®-III Automatic Transmission Fluid to bring the fluid level to the bottom of the threaded opening in the transmission oil pan.
  4. Start the engine.
  5. Add enough DEXRON®-III Automatic Transmission Fluid in order to bring the fluid level to the bottom of the threaded opening in the transmission oil pan.

Is the repair complete?

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Go to Road Test

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10

  1. Change the fluid and the oil filter.
  2. Add enough DEXRON®-III Automatic Transmission Fluid in order to bring the fluid level to the bottom of the threaded opening in the transmission oil pan.
  3. Start the engine.
  4. Add enough DEXRON-III Automatic Transmission Fluid in order to bring the fluid level to the bottom of the threaded opening in the transmission oil pan.

Is the repair complete?

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Go to Road Test

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