GarageDex

How to Check Transmission Fluid

Reviewed by GarageDex editorial

GarageDex's step-by-step guide covers the part most instructions skip: the check procedure changes by brand. Most automatics are checked warm, idling, in Park. Hondas are checked with the engine off. Many newer cars have no dipstick at all and are checked from underneath with a fill plug. The fluid type also changes by car, and putting the wrong one in is the fastest way to damage a transmission.

For your exact carFind your car's transmission fluid spec and capacityLook it up

Step by step

  1. Park on level ground and warm the transmission by driving for 10-15 minutes.
  2. Leave the engine idling in Park with the parking brake set (most cars). Some brands differ: Honda and Acura say engine off within a minute of warm-up, and many Chrysler, Dodge and Jeep automatics are checked in Neutral. Your owner's manual settles it.
  3. Pull the transmission dipstick (usually a red, yellow or orange loop near the back of the engine bay), wipe it clean, push it fully back in, and pull it again.
  4. Read the level against the HOT range. Check the color and smell on a white paper towel.
  5. If it is low, add the exact fluid your car specifies through the dipstick tube, a quarter of a quart at a time, and re-check. Overfilling causes foaming and slipping.

Use the fluid your car specifies, not "universal"

Automatic transmission fluid is not one product. Toyota WS, Honda DW-1, Ford Mercon LV, Dexron VI, ATF+4 and the CVT fluids are different chemistries, and a transmission built for one can slip or shudder on another. Look up the fluid spec and capacity for your year, make and model before you buy a bottle.

What you need

A clean rag or white paper towel to read the fluid, and, if you are topping up, a funnel with a long narrow neck that fits the dipstick tube.

Tools used in this guide

  • Long-neck transmission funnelFits the narrow dipstick tube so fluid goes in, not over the engineView on Amazon
  • Fluid transfer pumpFor sealed transmissions and differentials with a side fill plugView on Amazon

These tools fit any vehicle. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you.

Reading the dipstick

Most sticks have two ranges: COLD and HOT, or two sets of holes. Read the one that matches how you checked. A level anywhere inside the HOT range after a warm drive is fine. Below the bottom mark, add fluid. Above the top mark, the transmission was overfilled and should be drained back down: too much fluid foams, and foam does not lubricate.

Color and smell are the real check

Level tells you whether there is a leak. Color and smell tell you whether the fluid is still doing its job. New fluid is red and nearly transparent. It darkens with age. Once it is brown, opaque, or smells burnt, it is past due for a change, and if you see metal glitter in it the transmission is wearing internally.

When it is low

Transmission fluid does not get used up. If it is low, it left through a leak: the pan gasket, the cooler lines, an axle seal, or the dipstick tube seal. Top it up, then look for the drip, because running a transmission low is what turns a small leak into a rebuild.

Frequently asked

Do you check transmission fluid with the car running?

On most automatics, yes: engine idling, transmission warm, in Park. Honda and Acura are the common exception (engine off, within about a minute of shutting down after a warm drive), and many Chrysler-family automatics are read in Neutral. A cold or engine-off reading on a car that specifies hot and running will show a falsely low level.

What color should transmission fluid be?

Bright red to reddish-brown and clear is healthy. Dark brown or black fluid, a burnt smell, or visible metallic glitter means the fluid is worn or the transmission is wearing, and a fluid change is overdue. Milky pink fluid means coolant is getting in, which needs a shop the same week.

My car has no transmission dipstick. How do I check it?

Sealed transmissions (most 2010s-and-newer automatics and nearly all CVTs) are checked from underneath: the fluid must be at a specific temperature, read with a scan tool, and the level is set at a fill or check plug. That is a shop or a well-equipped DIY job, not a driveway check.

How much transmission fluid do I add if it is low?

A quarter of a quart at a time, re-checking between adds. The difference between the low and full marks on most dipsticks is only about a pint. Use only the fluid your manufacturer specifies for your transmission.

Need your car's exact spec?

Find your car's transmission fluid spec and capacity