Proper Way to Read a Transmission Dipstick

by Jody L. Campbell

Although easy in most vehicles, checking the transmission fluid is often neglected until a noticeable side effect occurs. Slipping gears or stains in the driveway can lead to irreversible damage to the transmission if it runs too low on fluid. Although the chemical properties of transmission fluid break down after time, the fluid remains at its proper level unless there is a problem. If you're checking the dipstick properly and have to continuously add transmission fluid, there's a leak in the system somewhere.

The Common Transmission Dipstick

Most transmissions are mounted to the back of the engine, so vehicles equipped with transmission dipsticks generally locate them on the lower side of the engine toward the back. The dipsticks may vary in handle colors, so be sure to refer to the owner's manual to correctly identify it.

The vehicle should be warmed up to operating temperature, be parked on level ground and have the engine idling. Apply the parking brake for safety. The dipstick is then extracted from the dipstick tube. Most transmission dipsticks are made of thin flexible metal and some can be very long and work their way to the transmission pan -- via the tube -- by some awkward angles. Try to pull the dipstick out slowly to get an accurate reading. Wipe the tip of the dipstick off with a shop rag and then look at both sides of the tip. There are many varieties of dipstick markings, but all employ the same procedure. A full level mark and a low level mark will be stamped on the bottom 2 inches of the stick. The full level reading is the farthest away from the tip and the low level is the closest to the tip.

Reinsert the dipstick (being careful not to get in the way of moving engine parts) carefully until it bottoms out in the dipstick tube. This can be harder to do on those long dipsticks that bend and turn through the tube. Once the dipstick is bottomed out, carefully remove it again. Be careful not to hit it with anything or you'll get a false reading by knocking off the fluid. Look at both sides of the dipstick and take the lowest reading as the actual transmission fluid level. It's a good idea to take three or four readings to make sure.

Different Types of Transmissions

It's not uncommon nowadays to find yourself looking all over the engine compartment for the transmission dipstick and getting frustrated with yourself. Read the owner's manual and you may discover that your automatic transmission vehicle does not feature a dipstick. So how do you go about checking the transmission fluid? These types of transmission generally require lifting the vehicle evenly on a commercial-type lift. A fill plug and a level plug may be located on the lower side of the transmission. The plug would be removed much like checking the fluid level in a differential.

And some newer cars have sealed transmissions that don't require checking or changing the fluid of until it needs a new transmission. The vehicles are designed with the dealership in mind to maintain and service the transmission.

Other types of transmissions that feature dipsticks may require checking the fluid level with the engine off. The dipstick reading will be similar, but it's best to check the owner's manual to perform the task correctly.

Having to Add Fluid

If fluid must be added, you'll need a small funnel and the correct transmission fluid for your vehicle. Different transmissions use specific fluid with different grades of properties and viscosity, so don't add just any old transmission fluid or damage can occur.

The dipstick tube acts as the fill hole. Place the funnel into the top of the dipstick and add a little bit at a time, depending on the reading of the dipstick. The engine still should be running when doing this on most vehicles. Once some fluid has been added, you'll need to allow the fluid to drain down into the tube. This can take in excess of five minutes or so to get an accurate reading on the dipstick. Otherwise, once you reinsert the dipstick, it will come into contact with the thick fluid draining down the tube and give you a false reading.

If you have to add fluid, it's wise to have the transmission seals, pan gasket and cooler lines inspected for any visible signs of leaking.

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