The automatic transmission filter in the Ford Focus is responsible for removing sludge and debris from the transmission. Over time, the filter itself saturates with these foreign materials and you must either back flush it or replace it. Even with back flushing, you need to replace the filter after every third flush. Ford Motor Company recommends servicing the automatic transmission in the Focus every 30,000 miles. Anyone with basic automotive-repair skills and an hour on their hands can perform this task.
Drive the Focus’ front wheels onto the ramps. Put the transmission in "Park," set the parking brake and shut the engine off. Place the wheel chock behind the back wheel.
Climb under the front end with the catch pan and socket set. Slide the catch pan under the bottom edge of the transmission pan and loosen the pan bolts with the socket set. Allow the transmission fluid to drain into the pan.
Remove the pan bolts with the socket set and put them aside within easy reach. Set the pan aside as well.
Scrap any remaining pan gasket material away from the bottom of the transmission with the gasket scraper. Scrape the pan itself in a similar manner.
Grab the filter and pull it down, out of the transmission. Set it in the catch pan. Push the new filter into place in the same orientation as the old one.
Climb out with the transmission pan and spray a light coating of spray adhesive on the sealing surface. Allow it to cure per the specific instructions on the adhesives container and then apply the pan gasket to the pan, making sure to line up all the bolt holes properly.
Slide back under the Focus and position the transmission pan against the bottom of the transmission, taking care not to jar the pan gasket loose. Thread the pan bolts in by hand and then tighten them down in a crossing pattern using the socket set.
Open the bonnet and pull the transmission dipstick out. Insert the funnel into the dipstick tube and pour in the transmission fluid, one quart at a time. Refer to the owner’s manual or service manual for your specific model year Focus for fluid capacity. On average, you can expect to pour in five to six quarts.
Remove the funnel and reinstall the dipstick. Start the engine and with your foot firmly depressing the brake pedal, shift the transmission from "Park" through each gear slowly and then back to "Park" Do not shift from one gear to the next until you feel the transmission respond to the prior shifting. Put it back in "Park" when done.
Pull the transmission dipstick, with the engine still running, and check the transmission fluid level. Top off as needed.