Street Smart - July - 2018

GM’s AF50 8-Speed Transmission Fluid Level and Condition Check

Remember the good old day’s when you just opened the hood pulled out the dipstick, wiped it off, stuck it back in, and pulled it out? Just like that, you knew if the fluid was low or not.

You could look at the fluid on the stick and tell a lot by its condition. Was it burnt, varnished, or nice and red? And if you needed to add fluid, you’d just grab a quart of Type F or Dexron off the shelf.

Those days are pretty much gone for good. Take a look at what you need to do to check the fluid on GM’s AF50 8-speed.


  1. Start the engine with the A/C off.
  2. Wait until the transmission fluid temperature reaches 35º–45ºC (95º–113ºF).
  3. Move the shift lever to all positions from park to drive, waiting at least two seconds at each position.
  4. Repeat step 3 and then shift back into park.
  5. Raise and support the vehicle. The vehicle must be level, with the engine running and the shift lever in park.
  6. Remove the fluid level plug on the bottom of the transmission, and see if the fluid dribbles out or not (figure 1). If not, the fluid is low.
  7. If you need to add fluid, use only the recommended automatic transmission fluid. This transmission requires AW-1 fluid.

It’s very important that the fluid is up to temperature. The AW-1 fluid is a full-synthetic fluid. It has a high expansion rate; if you don’t check it at the right temperature, it’ll create several problems.

If you check the fluid level when it’s too cold, when the transmission comes up to operating temperature, it’ll be overfilled. The fluid will make contact with the geartrain, which will aerate it, leading to shift troubles, converter shudder, and fluid leaking out the vent (figure 1).

Some residual automatic transmission fluid will dribble from the fluid level-setting hole when you first remove the plug; that’s normal.

Insufficient automatic transmission fluid level will cause the oil pump to draw in air, reducing line pressure. This causes clutches to slip, resulting in problems such as a burned clutches.

The fluid filler plugs installed at locations 1 and 2 (figure 2) from the vehicle assembly plant are one-time use. They have an interference fit and don’t have O-rings. You only need to remove one; whichever is easiest to reach.

Once removed, you must replace these plugs with new ones. The replacement plugs come with an O-ring. Lubricate the seal with AW-1 fluid and install the O-ring before installing the plug.

If no fluid comes out after you remove the plug and the temperature is within the specified range, add fluid until it runs out as a steady stream. Install and tighten the new transmission oil drain plug to 6lb-ft (8NM).

Check that the automatic transmission fluid is free of foreign matter. If the automatic transmission fluid is cloudy, suspect water contamination. Inspect the cooling system.

Caution: The antifreeze or water will deteriorate the seals, gaskets, and the glue that bonds the clutch material to the pressure plate. Both conditions may cause damage to the transmission.

If antifreeze or water has entered the transmission:

  1. Repair the source of the water; usually the leak is from the transmission cooler in the radiator or it could be a water leak through the vent.
  2. Replace all of the rubber seals. The coolant will attack the seal material, which will cause leaks.
  3. Replace the torque converter.
  4. Flush the cooler lines.

Check that the automatic transmission fluid isn’t discolored.

You can’t change the transmission filter to help increase the life of your transmission. Changing the transmission fluid will help.

It is important not to mix fluid. Use the correct, AW-1 fluid only.

And that’s not just smart: that’s street smart.