The following covers Mitsubishi Galant models from 1990 through 2000. Mitsubishi recommends that you use Mercon automatic transmission fluid. Check the owner's manual to confirm the recommended transmission maintenance schedule. If you drive the Galant under severe service, you should change the automatic transmission fluid twice as often as you would if you drove the car under normal service.
Drive the Galant for 20 minutes to heat up the transmission fluid. Park the car on level ground, raise and support it with jack stands. Place a large drain pan beneath the transmission. If there is a drain plug on the fluid pan, remove it and allow the fluid to drain. Use an appropriately sized socket wrench to remove the fluid pan retaining bolts.
Lower the fluid pan from the transmission. Remove the gasket from the fluid pan, clean the pan with a safe solvent and set it aside to air dry. Discard the gasket. Use the socket wrench to remove the fluid filter retaining bolts and pull the filter from the valve body.
Install a new fluid filter and tighten the retaining bolts to 5 ft-lbs with a torque wrench. Position a new gasket onto the fluid pan and reinstall the pan onto the transmission. Tighten the bolts evenly to 8 to 9 ft-lb. Use care not to overtighten them. Return the vehicle to the ground.
Measure the amount of fluid that you drained from the transmission. Pour the same amount of new automatic transmission fluid into the transmission through the dipstick filler tube. You will need a funnel with a long neck for this step.
Move the gear selector to "Park," apply the parking brake, put wheel blocks on the front wheels and start the engine. Let the car idle for a few minutes. Check the fluid level with the dipstick. Add more fluid if needed. If not, take the Galant for a short drive. Return the car to a level surface and recheck the fluid level. If needed, add more fluid to bring the fluid level to the correct position on the dipstick. Depending on your vehicle, the dipstick may read "Hot" and "Add" or "Min" and "Max." Either way, the fluid level should fall between the two indicators.
