Transmission fluid is a liquid that acts as a lubricant for all of the moving parts inside your transmission. In an automatic transmission, this fluid also serves as a coolant and a viscous fluid that transmits power from the engine to the transmission. This fluid eventually becomes contaminated with small particles created by the wear of moving parts and breakdown of chemical properties and needs to be changed.
There are a few reasons why you need to maintain your transmission fluid and they are specific to which type of transmission your vehicle has. Despite the significant advancements in modern transmissions and the “fill-for-life” fluids used by some manufacturers, transmission experts say fluid should be periodically changed to ensure maximum transmission life.
In a manual transmission, the problem is not so much the fluid degradation, but rather fluid contamination. This contamination occurs over time as the synchronizers, bearings and gears in the transmission wear. The resulting metal particles then float around in the lubricant. And we all know that oil with microscopic particles of metal in it does not lubricate as well as clean oil. So if these contaminants are not drained out, they will shorten the life of your transmission.
Because more heat is generated in an automatic transmission, automatic transmission fluid actually degrades and breaks down with use.
In addition, like in a manual transmission, automatic transmission fluid will also become contaminated with worn bits of the transmission planetary gears and clutch materials. If these contaminants are not drained out, they will shorten the life of your transmission.
If you don’t change the transmission fluid on schedule, you’ll be lubricating your transmission with metal shavings and other contaminants. This will shorten the transmission’s life. With the average cost of a transmission replacement at over $3000, regular transmission fluid flushes are a sound investment.
Between fluid flushes it is a good idea to regularly check the fluid level. Letting your car run low on transmission can cause your car to shift improperly or not at all. You may not hear any noises or have any clues that your transmission fluid is running low until it is too late, so it is important to check.