Many people today, in an attempt to save money, are not doing routine maintenance on their vehicles. In the long run it may cost them much more in expensive repairs. The transmission is one of those assemblies that often does not get the service it requires.Transmission fluid does break down after long term use and can loose some of its lubrication properties. It should be changed every 50,000 miles, or more often if the vehicle is used for heavy towing.
What you will need
Before you begin work on the vehicle, go to the parts store and purchase a filter, gasket, and seal kit for the vehicle. The Chevy Monte Carlo with the 3.8 liter engine takes about 7 quarts of transmission fluid, I use a good quality Dexron III ATF. You will also need jack stands or ramps to support the car while you work. Have a pan that can hold a couple of gallons of waste oil and a way to measure the amount of transmission fluid you remove. Make sure you know where you can recycle the waste fluid from the transmission, do not just dump the oil on the ground or pour down the sewer.
Getting Started
The first thing we do is jack the car up and place the jack stands to make the vehicle safe for working underneath. The transmission pan should be located directly behind the engine pan. Make sure the vehicle is not too hot when you start work. With the waste oil pan in place under the transmission, start removing the back and side transmission pan mounting bolts. Don’t remove the front bolts, just loosen them about two turns. Now pry the pan loose in back and let the fluid drain. After most of the fluid has drained remove the remaining bolts and dump the transmission pan into your waste container.
Cleaning the transmission pan
Take a clean shop rag and start wiping the inside of the transmission pan. Also clean the lip where the gasket was fitted to the transmission, make sure you remove any sealant or dirt that remains after the gasket has been removed. At the bottom of the pan should be a little square magnet, pull it out and clean it then reinstall.
Filter change
Twist the filter back forth a little and pull it out of its seal. With a screw driver pry the old seal out. Push the new filter seal into its bore, you might need to use the right sized socket and hammer to lightly tap the seal in place. Push the new filter into the filter seal. Place the new gasket onto the transmission pan and hold it in place against the transmission. Install the bolts, go around the pan and tighten each only a couple of turns at a time until all are tight. You can check with a torque wrench(100 inch pounds should do it) if you have one, or make sure they are snug but do not over tighten and strip out the bolts.
Adding and checking fluid
Measure the waste fluid that you collected, this will give you idea of how much new fluid you should put in the transmission. After adding fluid remove jack stands and start the vehicle. With the parking brake on, move the shift lever through each gear and then back to park. Check the fluid level. Take the vehicle for a test drive and check for leaks. Both you and your car should be good to go.