Warm up the transmission by driving the vehicle briefly
Park on a level surface
Set the parking brake
Raise and support the vehicle safely if needed
Place a drain pan under the transmission pan or drain plug
Remove the drain plug or loosen the pan bolts to drain the fluid
Remove the transmission pan if required
Clean the pan and magnets
Replace the transmission filter and gasket if applicable
Reinstall the pan and tighten bolts to specification
Refill with the correct type and amount of automatic transmission fluid
Start the engine and cycle through all gear positions
Check the fluid level with the engine running and transmission at operating temperature
Add fluid as needed to reach the proper level
Inspect for leaks
Repeat drain-and-refill cycles if a full flush is desired
Use a transmission flush machine only if recommended by the vehicle manufacturer