Pontiac Fiero 1984-1988 Repair Guide

Automatic Transaxle



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Fig. Fig. 1 THM 125C automatic transmission dipstick. The level should be in the cross hatched area when the vehicle is parked on a level surface and at normal operating temperature

The automatic transaxle fluid level should be checked at each engine oil change. When adding or changing the automatic transaxle fluid use only fluid labeled Dexron® II.

  1. Set the parking brake and start the engine with the transaxle in "P" (Park).
  3. With the service brakes applied, move the shift lever through all the gear ranges, ending in "P" (Park).

The fluid level must be checked with the engine running at slow idle, the car level and the fluid at least at room temperature.

The correct fluid level cannot be read if you have just driven the car for a long time at high speed, city traffic in hot weather or if the car has been pulling a trailer. In these cases, wait at least 30 minutes for the fluid to cool down.

  1. Remove the dipstick located at the rear end of the engine compartment, wipe it clean, then push it back in until the cap seats.
  3. Pull the dipstick out and read the fluid level. The level should be in the cross-hatched area of the dipstick.
  5. Add fluid using a long plastic funnel in the dipstick tube. Keep in mind that it only takes one pint of fluid to raise the level from "ADD" to "FULL" with a hot transaxle.

Damage to the automatic transaxle may result if the fluid level is above the "FULL" mark. Remove excess fluid by threading a small rubber hose into the dipstick tube and pump the fluid out with a syphon pump.


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Fig. Fig. 2 Exploded view of the automatic transmission pan and gasket

According to Pontiac, under normal operating conditions the automatic transmission fluid only needs to be changed every 100,000 miles unless one or more of the following driving conditions is encountered. In the following cases the fluid and filter should be changed every 15,000 miles:

  1. Driving in heavy traffic when the outside temperature reaches 90°F.
  3. Driving regularly in hilly or mountainous areas.
  5. Towing a trailer.
  7. Using a vehicle as a taxi or police car or for delivery purposes.

Remember, these are factory recommendations, and in this case are considered to be minimum. You must determine a change interval which fits your driving habits. If your vehicle is never subjected to these conditions, a 100,000 mile change interval is adequate. If you are a normal driver, a 2-year/30,000 mile interval will be more than sufficient to maintain the long life for which your automatic transaxle was designed.

Use only fluid labeled Dexron® II. Use of other fluids could cause erratic shifting and transmission damage.

  1. Jack up your vehicle and support it safely with jackstands.
  3. Disconnect the negative (-) battery cable.
  5. Remove the front and side pan bolts.
  7. Loosen the rear bolts about four turns.
  9. Carefully pry the oil pan loose and allow the fluid to drain.
  11. Remove the remaining bolts, the pan, and the gasket or RTV sealant. Discard the old gasket.
  13. Clean the pan with solvent and dry it thoroughly, with compressed air.
  15. Remove the strainer and O-ring seal.
  17. Install a new transaxle filter and O-ring seal, locating the strainer against the dipstick stop.

Always replace the filter with a new one. Do not attempt to clean the old one.

  1. Install a new gasket or RTV sealant then tighten the pan bolts to 12 ft. lb. (15 Nm).
  3. Lower the car and add about 4 quarts of Dexron®II transmission fluid.
  5. Start the engine and let idle. Block the wheels and apply the parking brake.
  7. Move the shift lever through the ranges. With the lever in "PARK", check the fluid level and add as necessary.

The transmission fluid currently being used may appear to be darker and have a strong odor. This is normal and not a sign of required maintenance or transmission failure.