How To Check Automatic Transmission Fluid

What is transmission fluid?

Transmission fluid lubricates the components of your transmission system to keep everything functioning smoothly. As you use your gears over time, the fluid level can fall and need to be topped up.

While both manual and automatic cars need transmission oil, each engine uses a different type, so it’s important to make sure you’re using the right one. Manual transmission fluid is typically darker and thicker, as it needs to lubricate a heavier duty gearing system. Automatic transmission fluid is usually lighter and thinner as it must travel through very small oil galleries.

Since transmission fluid is so important to your vehicle’s function, you should try to check your fluid level around once a year to every two years.

Note: Many modern vehicles use a sealed transmission system that doesn’t require checking or topping up. Consult your owner’s manual to see if your make and model has a transmission dipstick.

How to check and top up automatic transmission fluid

What you'll need

  • A cloth/rag
  • Transmission fluid that’s suitable for your car – consult your owner’s manual to find out what type you need
  • A funnel (if needed)

Step 1: Prepare your car

For the most accurate reading, most transmission systems should be checked while they’re warm. Before completing the check, start your engine and leave it running for around ten minutes to give the fluid time to warm up. Leave the car running throughout the check, out of gear with the handbrake on. A short road test would also help here.

You should also park your car on a flat surface for an accurate measure.

Step 2: Locate the transmission fluid dipstick

First, you’ll need to find the transmission fluid dipstick. Open the bonnet and look for a yellow or orange round handle – it should look similar to your oil dipstick.

Step 3: Wipe the residue

Remove the dipstick and wipe it clean with your cloth before reinserting it. This will help to give an accurate reading.

Step 4: Check the dipstick

Remove the dipstick again to measure the fresh level of fluid.

Look at how far up the dipstick the fluid reaches. The stick will feature two lines or dots a set distance apart which indicate the safe parameter of transmission fluid – your fluid level should sit somewhere within this gap.

If the fluid level sits below the lowest line, then it will need to be topped up.

How to top up transmission fluid

If you do need to top up your transmission fluid, you can use a funnel to add more fluid via the tube the dipstick sits in. Make sure to keep putting the dipstick back in to check the fluid level to make sure you don’t overfill.

Here at Halfords, we have transmission fluid for both automatic and manual cars. To find the right one for you, just enter your car registration number into our handy online tool, to be shown all the types that are compatible with your vehicle.