Changing transmission fluid & filter

Part 1. Preparation and safety

Objective

• Change automatic transmission/transaxle fluid.

Personal safety

Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:

• Work clothing - such as coveralls and steel-capped footwear
• Eye protection - such as safety glasses and face masks
• Ear protection - such as earmuffs and earplugs
• Hand protection - such as rubber gloves and barrier cream
• Respiratory equipment - such as face masks and valved respirators

If you are not certain what is appropriate or required, ask your supervisor.

Safety check

• Do not put your finger into the filler plug opening to check the fluid level if the transmission is rotating, either by the engine or by some person turning the drive wheels.
• If the vehicle has been driven prior to checking the fluid level, the fluid could be very hot. Be careful not to burn yourself on this hot fluid.
• Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.

Points to note

• You will need to refer to the owner's manual for the specified intervals for lubricant servicing.
• If the engine is cold, the vehicle may need to be driven a short distance to bring the oil to normal operating temperature. Any contaminants in the fluid will flow out more readily with a warm to hot fluid.
• Selecting and using the correct type and grade of lubricant is critical. The wrong selection can lead to premature failure of the internal components.
• A correct fluid level is critical to effective and efficient operation. If the level is too high, it will cause the fluid to churn and aerate, causing air bubbles that can trap heat and make the fluid run hotter. This can lead to early failure of bearings or gears.
• A low fluid level can cause as many problems as a high fluid level. Air can enter the system and heat generation can burn vital internal components.

Part 2: Step-by-step instruction

1. Prepare to drain lubricant
   Warm up the transmission fluid by idling or driving the vehicle. Raise the vehicle, and ensuring that it is level and stable, do a visual inspection for leaks from the transmission. Most transaxles have drain plugs fitted to them that are easily accessible. However, some require that a housing be removed in order to drain the oil. Other types do not have drain plugs, and require a suction pump to draw out the lubricant by hand from the filling point. Consult the shop manual for correct procedures for draining the fluid on the vehicle you are working on. Be careful because the lubricant can be hot enough to burn.
2. Drain lubricant using drain plug
   Locate the position of the drain plug and remove any guard covers if necessary. Select the correct wrench and loosen the plug. Position a large diameter drain pan under the transmission, clean the plug, and then remove it.
3. Draining auto transmission without drain plug
   In the case of an automatic transmission, if there is no drain plug, loosen all the transmission pan bolts, with the correct wrench and remove all but three, the minimum necessary to hold the pan in place. Fluid will flow into the drain pan. Once the fluid stops flowing from the bolt holes, support the transmission pan with one hand, and remove the remaining bolts to drain the remaining oil.
4. Examine lubricant and pan
   Look for metal in the fluid, which looks like shiny particles or flakes. If the transmission has been overfilled during service, it could have caused internal damage to components. Also inspect the transmission pan and the residue in it. A small amount of metal deposits is normal, but a build-up could signal excessive transmission wear. If you find larger pieces of metal or clutch material that looks a lot like brake lining material in the case of an automatic transmission, have your supervisor come and inspect it. It is good practice to keep these larger particles in case the owner wants to see them.
5. Clean auto transmission oil pan gasket and filter screen
   With an automatic transmission, carefully remove the oil pan gasket. Don’t use a sharp tool that could damage the sealing surface. Clean the pan with a lint-free cloth, and remove the transmission filter. Filters and screens may be held in place by several screws of varying sizes. Be careful to note any size differences of the screws so you can reinstall them in the correct position. If you have a paper or cotton filter in the transmission, it must be changed every time you change the transmission fluid. Metal filters can be cleaned with solvent or a spray cleaner and reused after air-drying.
6. Replace auto transmission filter and oil pan gasket
   Install the new filter on the valve body as described in the shop manual. Place the new gasket on the sealing surface of the fluid pan. Apply the manufacturer’s recommended sealant to the gasket if needed.
7. Clean and re-install drain plug
   Replace the transmission or sump pan, and tighten the bolts to the manufacturer-specified torque. Over tightening the bolts may damage the gasket and/or the sealing surfaces. After the lubricant is completely drained, clean the drain plug. Put the drain plug back with a new washer. Use a torque wrench to make sure the torque is correct.
8. Pump in new lubricant
   Check the shop manual’s lubrication guide for the correct replacement fluid specification and the correct quantity. If the filling location is under the hood, you will need to lower the vehicle. Clean the nozzle of a lubricant pump with a clean lint free rag or paper towel. Use the pump to put new transmission oil into the filler hole or dipstick tube opening. Pause for a few seconds after each pump, to give the lubricant time to flow to the bottom. Stop when the lubricant reaches the bottom of the filler plug hole, or to the top of the cold mark on the dipstick.
9. Move through the gears (auto)
   In the case of an automatic transmission, start the engine. Apply the foot brake, and move the transmission selector through all the gear selections. This will allow all the cavities in the transmission to fill with new fluid. Place the transmission in the correct gear for fluid checking.
10. Check the new fluid level
    Check the new fluid level. Adjust if necessary and replace the dipstick or filler plug.