According to Ford maintenance guidelines, you should change the automatic transmission fluid in your Focus every 48,280 km (30,000 miles) if it is used under normal operating conditions. If you do a lot of towing with your Focus, it is recommended that you change the automatic transmission fluid every 24,140 km (15,000 miles).
Drive your Ford Focus for ten minutes to warm up the transmission fluid. Park on a level spot. Turn off the engine. Engage the hand brake. Open the bonnet and secure it using the safety bar.
Check the automatic transmission fluid (ATF) level and quality. The dipstick is located toward the rear of the engine. It is marked ATF Engine Oil or Transmission Fluid. Pull this dipstick out. Wipe it off with a clean paper towel. Look at the fluid on the paper towel. Transmission fluid needs to be replaced if it is brown. Fresh transmission fluid is translucent red. Replace the dipstick. Pull it out again and look at the level. It should be between the MIN and MAX lines. In some models manufactured prior to 2005, there is no dipstick. This is called a closed system. In this case, you will have to proceed with changing the ATF without checking the level and quality.
Lift the front of your vehicle up with a floor jack. Use jack stands placed under the lift notch about 15 cm (6 inches) behind the front wheel well on either side of the vehicle. Lock the jack stands in place by lowering the security bar.
Disconnect the fluid line that links the transmission to the radiator by loosening the clamp with an adjustable spanner and then pulling on the line gently. The ATF will be hot, so be careful that you don't burn yourself. The transmission is attached to the dipstick well. Place the open end of this line into an empty container, such as an engine oil drain pan.
Start the engine. Make sure that you leave the hand brake engaged. Watch the ATF line to see when the ATF stops flowing. Turn off the engine as soon as the flow of ATF stops. Reattach the line to the transmission.
Remove the drain pan. You will have to get under the vehicle to do this. Directly under the transmission, you will see a solid plate with bolts all around the edges. Remove the bolts using a 8 mm (5/16 inch) hex socket. Some additional ATF may spill when you do this. Remember that it will be hot. Peel the gasket from the rim of the drain pan.
Wipe out the bottom of the drain pan with a clean paper towel. If it is really dirty, you may need to pour a little transmission fluid on it to help remove some of the sludge. Using water to clean the pan is a bad idea as water will damage the transmission.
Locate the 18 mm (11/16 inch) lock nut on the bottom of the transmission filter. This is located in opening which became visible when you removed the drain pan. Remove the lock nut using 18 mm (11/16 inch) box end socket. Pull the filter down to remove it.
Install a new filter by sliding it into the filter port. Tighten the lock nut until it is secure.
Place a new gasket on the drain pan and then position the drain pan so you can replace the bolts. Tighten these by hand until all of the bolts are holding the drain pan. Moving in criss cross pattern, tighten the bolts using the 8 mm (5/16 inch) hex socket until they are secure. Keep in mind that over tightening will dent the drain pain.
Unlock the jack stands and remove them. Lower your vehicle using the floor jack.
Check the engine specification sticker located on the interior of the bonnet for the ATF specifications. This varies according to manufacture year and engine size. The sticker should tell you the type of ATF and the amount needed for your vehicle. If you are unable to find the sticker, the information is also in the owner's manual.
Locate the ATF fill port. This is located beside the dipstick. Remove the black cap marked ATF or Transmission Engine Oil.
Place a funnel in the fill port. Pour the appropriate amount of ATF into the funnel. Check the level again. If it is low, add a little more ATF and recheck.
Replace the black cap and tighten it. Close the hood. Start the vehicle and allow it to idle for ten minutes to circulate the ATF.
If the ATF is low when you check the level, there is more than likely a leak in the system. You must have the system serviced before you change the fluid.