Automatic Transmission Fluid: How it Works, Types, and Problems

16 November 2021
 Categories: , Blog

Your car's automatic transmission depends on its fluids. When you have a leak or other fluid problem, your transmission will fail to work. You may wonder what the automatic transmission fluid does. Also, you may want to know whether you can use manual and automatic transmission fluid interchangeably.

Continue reading to learn more about the purpose of automatic transmission fluid. Also, find out why it's important to keep your vehicle's fluids in good condition.

What does automatic transmission fluid do?

Automatic transmission fluid does several things for your transmission. Below is a list of some of its functions.


One job of automatic transmission fluid lubricating all the gears and seals inside the unit. Without it, friction between those parts will melt the metal and seize.


Automatic transmission fluid moves dirt and debris out and away from the gears and bands.


The transmission's fluid dissipates heat and keeps temperatures down.


Unlike manual transmission, an automatic transmission needs pressurised fluid to change gears. It uses a pressurised torque converter instead of a manual lever for shift changes.

What are the types of automatic transmission fluid?

Be careful when you purchase automatic transmission fluid as there are many different kinds. If you put in the wrong one, you could risk transmission damage. Some types of automatic transmission fluid include:

  • Dextron/Mercon fluid is what most newer vehicles use.
  • Type F for Ford vehicles.
  • Highly friction modified (HFM) which are similar to Dextron/Mercon
  • Synthetic fluids
  • Continuously variable transmission (CVT) fluid

Is there a difference between manual and automatic transmission fluid?

Generally, automatic transmission fluid has a lower viscosity than manual transmission fluid. This low viscosity allows the fluid to flow easily through the system. Manual transmission fluid's high viscosity could prevent shifting and provide enough internal protection. Likewise, automatic transmission fluid could also cause problems with manual shifting. Therefore, do not use the fluid for the other type unless your manufacturer recommends it.

What happens when a vehicle has a fluid problem?

When you have a problem with the automatic transmission fluid, your vehicle could have trouble shifting. When your fluid is low, for example, you may experience delayed shifts. Old, burned, or contaminated fluid can also cause shifting problems. Therefore, fluid maintenance is key to keeping your transmission working.

When your vehicle has a problem with its automatic transmission fluid, don't hesitate to see a mechanic. When your fluid is in poor condition, or your fluid levels are low, you could risk damaging your transmission. In some cases, automatic transmission damage is unfixable, so you will need a new transmission. For more information about transmission and for a vehicle checkup, seek an auto shop's help.