Transmission Fluid


The transmission's fluid and filter should be changed whenever there is an indication of oxidation or contamination. periodic fluid and filter changes are also part of the preventative program for most vehicles. the frequency of this service depends on the conditions under which the transmission normally operates. severe usage requires that the fluid and filter be changed every 15,000 miles (24,000 km). severe usage is defined as more than 50% operation in heavy city traffic during hot weather above 90°f (32°c) or police, taxi, commercial-type operation, and trailer towing.

Change the fluid only when the engine and transmission are at normal operating temperatures. on most transmissions, you must remove the oil pan - transmission to drain the fluid. some transmission pans on recent vehicles include a drain plug.

Changing Transmission Fluid

When changing transmission fluid, check the service manual for special instructions. Some manufacturers call for draining the converter also. Most transmissions do not have drain plugs in the converter, so they do not require a complete change of the fluid. Only the automatic transmission fluid (ATF) in the pan is removed. Adding new fluid after the pan is reinstalled replenishes any additives that have been depleted during service.

  • To drain and refill a typical transmission, the vehicle must be raised on a hoist.
  • After the vehicle is safely in position, place a drain pan with a large opening under the transmission's oil pan.
To lessen the mess, use a hand held fluid transfer pump to drain most of the fluid through the dipstick tube before removing the transmission oil pan.
  • Then loosen the pan bolts and tap the pan at one corner to break it loose. Fluid will begin to drain from around the pan.
  • After draining, carefully remove the pan. There will be some fluid left in the pan. Be prepared to dump it into the drain pan.
  • Use a magnet to determine if metal particles are steel or aluminum.
    • Steel particles indicate severe internal transmission wear or damage.
    • If the metal particles are aluminum, they may be part of the torque-converter stator. Some torque converters use phenolic plastic stators, therefore metal particles found in these transmissions must be from the transmission itself.
  • When adding fluid, be sure to use the correct type.
  • Add fluid through the dipstick hole with a funnel with a small opening that will fit into the dipstick tube. Be sure the funnel is clean.
A funnel that has had oil in it will collect shop dust. After use, rinse it and keep it in a plastic bag.