GM Firebird 1967-1981 Repair Guide

Manual Transmission



The oil in the manual transmission should be checked at least every 6,000 miles for 1967-74 models or every 7,500 miles for all 1975 and later models.

  1. With the car parked on a level surface, remove the filler plug from the side of the transmission housing.
  3. If the lubricant begins to trickle out of the hole, there is enough and you need not go any further. Otherwise, carefully insert your finger (watch out for sharp threads) and check to see if the oil is up to the edge of the hole.
  5. If not, add oil through the hole until the level is at the edge of the hole. Most gear lubricants come in a plastic squeeze bottle with a nozzle; making additions simple. You can also use a common kitchen baster. Use only standard GL-5 hypoid-type gear oil SAE 80W or SAE 80W/90.
  7. Replace the filler plug, run the engine and check for leaks.


There is no recommended interval for the manual transmission, but it is always a good idea to change the fluid if you have purchased the car used, or if it has been driven in water high enough to reach the axles.

  1. The oil must be hot before it is drained. Drive the car until the engine reaches normal operating temperature.
  3. Remove the filler plug to provide a vent.
  5. Place a large container underneath the transmission and remove the drain plug.
  7. Allow the oil to drain completely. Clean off the drain plug and replace it; tighten it until it is just snug.
  9. Fill the transmission with the proper lubricant. Refer to the "Capacities" chart for the correct amount of lubricant.
  11. When the oil level is up to the edge of the filler hole, replace the filler plug. Drive the car for a few minutes, stop, and check for any leaks.