Your owner's manual may claim that you don't need to change the fluid in your automatic transmission. However, this is one area in which it pays to err on the conservative side. If you understand what happens to the fluid as it courses through your transmission, you'll appreciate why changing it can prolong the assembly's life. Given that the cost of overhauling or replacing a tranny can rise to ,500 or more, it's worth taking the time to check the level and quality of the fluid.
This article will explain why the ATF needs to be changed periodically, despite what your owner's manual may suggest. You'll learn how to check the fluid, and identify signs that indicate it has degraded past the point of serving its purpose. We'll also explain how to purchase the right type of ATF for your vehicle.
Why The Fluid Needs To Be Replaced
While you're on the road, your transmission generates friction among its moving parts. The torque converter, gears, clutches, bands, and other pieces, are in near-constant motion. The friction they cause generates a substantial amount of heat. This heat is the reason ATF degrades over tens of thousands of miles.
Most ATFs can tolerate temperatures up to 195 degrees Fahrenheit without suffering significant degradation. Under normal driving conditions, the temperature surrounding your tranny should stay well below this marker. As long as it does, the ATF can last 50,000 or more miles without needing to be replaced.
The problem is, most of us drive in conditions - even if only occasionally - that cause the temperature around the assembly to rise higher. For example, we might drive up inclines, at fast speeds, or while towing heavy loads. This can cause the temperature to rise to 250 degrees Fahrenheit, or higher. When this happens, the ATF undergoes oxidation. It breaks down, and loses its ability to lubricate the individual parts inside your transmission. At that point, if you neglect to change it, the assembly will eventually suffer damage.
This is the reason many technicians recommend replacing the fluid every 25,000 to 30,000 miles. If you regularly tow heavy loads, or drive in extreme conditions, change the ATF on an annual basis.
How To Check The Fluid
Most people are accustomed to checking their oil level with their engines turned off. When you check the transmission fluid, let your engine idle while the gear selector is in "Park."
You'll find the dipstick located near the oil dipstick. Have a paper towel handy. Withdraw the dipstick, and wipe it clean. Then, insert it back into its housing, and withdraw it again. You'll see two lines on the bottom end. One will be marked "Full"; the other will be marked "Add." If the level is at "Add" or below, put more ATF in the reservoir.
Take the opportunity to check the color and consistency of the fluid. Even though this can be done by looking at the dipstick, both qualities are easier to determine by placing a few drops on a clean surface. If the ATF has a reddish tint, and runs easily (similar to table syrup), it's in good condition. If the fluid has a brownish tint, and muddy consistency, it needs to be replaced.
Choosing The Right Fluid For Your Transmission
There are dozens of ATFs you can purchase. However, your car's transmission is designed to use a specific type. For example, Type CJ should be used in certain kinds of Ford transmissions; Chrysler 7176 is designed for that particular automaker's front-wheel drive vehicles; and Mercon V should be used in most Ford models built after 2000.
The important thing to keep in mind is that the wrong fluid can set the stage for premature wear and damage in your transmission. Look in your owner's manual to find the appropriate ATF for your vehicle. Stick closely to that type.
Don't neglect to periodically check the fluid in your automatic transmission, and change it if necessary. It is one of the least expensive ways to ensure the assembly lasts as long as possible.
