How to Change Transmission Fluid in an Aleroby Lee Sallings; Updated November 07, 2017
Items you will need
Jack stands (two pairs)
Filter and gasket kit
Dextron 3 transmission fluid
The transmission in the Oldsmobile Alero is a closed system and doesn't have a dipstick for checking fluid level and condition. For this reason it is even more important to change the fluid at the service interval indicated in your owners manual. Vehicles that are driven under heavy driving conditions such as heavy traffic should have the transmission fluid and filter changed at least every 50,000 miles. Changing the fluid and filter is well within the average home mechanic's ability, even with the different fill procedure.
Lift the front of the Alero with a floor jack and position two jack stands under the front sub frame. Lower the car onto the jack stands, and remove the jack from under the car. Raise the rear of the car with the floor jack and position the other pair of jack stands under the rear sub frame. It is important for the vehicle to be level when it is on the stands when adding the fluid to the transmission.
Place a drain pan under the transmission pan and remove the 10 mm bolts attaching the pan to the transmission. Remove the last few bolts slowly, and hold the pan in place, to prevent accidental spillage of fluid if the pan drops suddenly. Lower the pan into the drain pan. Remove the transmission filter by rotating the filter while pulling down. Additional fluid will drain out when the filter is removed. Use a screwdriver to pry out the orange rubber seal in the hole that the filter plugs into.
Push the new seal that comes with the transmission kit into the transmission where the filter snaps in. Push the new filter into the seal until it seats fully. A few taps with the palm of your hand may be needed to seat the filter completely.
Remove the old gasket from the transmission pan and the transmission sealing surface. Attach the transmission pan gasket to the pan using adhesive. Bolt the pan into place on the transmission and tighten the bolts snugly. Avoid over-tightening the bolt to prevent splitting the gasket and causing it to leak.
Remove the check plug on the transmission case, located bellow and slightly in-board of where the passenger side drive axle plugs into the transmission. This can be a little difficult to remove because it is between the engine and transmission and there is not much room to maneuver.
Remove the large red fill plug located on top of the transmission. This is accessible from under the hood. Inset the transmission funnel into the fill opening and add Dextron 3 transmission fluid until it runs out the check plug. Replace the check plug, and the fill plug. Lower the vehicle from the jack stands and test drive.