Changing Transmission Fluid: It’s a Dirty Job But Somebody’s Gotta Do It

Nobody likes crawling under their vehicle to change transmission fluid, especially if it’s an automatic that requires the whole pan to be dropped. It’s a messy job—and as the weather turns colder, it’s one that gets pushed off more and more. Even as auto aficionados, we can get lazy when it comes to routine maintenance tasks that don’t offer brag-worthy upgrades. (Really, who’s inviting their buddy over to take a peek under the hood at the sweet job they did changing transmission fluid?)

As uninspiring as the task can be, it’s one of the most important things you can do to maintain the life of your ride. Besides, the awful feeling of slipping gears and jerking around during shifting is more than enough to drive you nuts. Truth is, there’s no harm in changing transmission fluid more often than recommended. But at the very least, you should understand what those recommendations are, and how you can keep the guts of the gearbox in pristine condition.

Automatic Transmissions

Automatic and manual transmission fluids work in very different ways. Additionally, there are several grade qualities within those two categories that address things like pressure and temperature differently. But with the majority of American daily drivers operating an automatic transmission, let’s start with how traditional ATF, or Automatic Transmission Fluid works.

In simplest terms, automatic transmissions operate on hydraulic pressure to shift gears. The ATF works as the hydraulic fluid. A torque converter spins, pressurizing the fluid and forcing the gears to shift. The system itself is significantly more intricate, but you get the general idea: transmission fluid plays an extremely important role.

Not only does the fluid affect rotational speed, it also acts as a coolant. Additionally, it lubricates and protects internal parts of the transmission. In essence, it doubles as a working part. A working part that is exposed to high temperatures, high pressure, and plenty of friction.

Those temperatures will cause the fluid to break down over time, and the debris from worn internal parts will contaminate the fluid. According to award-winning radio show Car Talk, “Service intervals for an automatic transmission vary from every 30,000 miles … to never. The typical service interval is 60,000 to 100,000 miles.”

Check your vehicle’s service manual to find out the OE recommendation for your ride. And keep in mind that changing transmission fluid more often does no harm—especially if you’re beating on that car or truck.

Manual Transmissions

Unlike automatic transmissions, manuals use a clutch pedal to unlock the gears for shifting. And while manual transmissions can use a variety of oils, they need to be replaced more frequently than their automatic siblings. As Car Talk explains, “The problem is not so much fluid degradation, but rather fluid contamination.”

As internal parts of the transmission see more friction, they wear down faster. And as metal particles begin floating around in the fluid, it stands a good chance of ruining your transmission. Most manufacturers suggest changing transmission fluid in manuals every 30,000-60,000 miles. And of course, under hard use, you will want to replace the fluid more often.

Did You Know? Cold weather can impact the driving quality of manual transmissions quite severely. Amsoil warns that “as transmission fluid thickens in the cold, the synchronizers in manual transmissions cannot spin as quickly as they need to, which can severely impact the driver’s ability to shift until the fluid is warmed enough to provide proper flow – and protection.” They recommend using a wax-free lubricant, like Amsoil-brand transmission fluids, to combat cold-flow issues.

Signs It’s Time for a Change

Truly, no one enjoys changing transmission fluid, but ignoring it could mean some major pain for your wallet. A professional has the proper tools and workspace to perform the job best, but with some auto know-how you can tackle this one yourself. At the very least, you can learn what signs to watch out for and how to check fluid levels.

If you’ve noticed a delay, grinding sound, or general roughness when shifting, it’s time to get your ride checked out. Other symptoms include: burning smell, unusual sounds, a surging or lurching feeling, and a big ol’ illuminated CHECK ENGINE light.

Checking transmission fluid can be a little tricky depending on your vehicle, although most manufacturers provide a labeled dipstick under the hood. For automatics, pull the transmission dipstick out while the engine is warm, running, and in park. Wipe it clean with a lint-free rag, reinsert and remove again. The fluid should have a clear pinkish hue and be free of particles. If the fluid doesn’t reach the marked line on the dipstick, you’ll need to add more. Keep in mind though, that this could be a sign of a leak, in which case you should consult a professional. Additionally, if the fluid has a burnt smell, it most definitely needs a closer inspection.

Most all manual transmissions require the vehicle to be lifted because a filler plug must be removed in order to check the fluid level. AutoBlog provides an excellent step-by-step process here for those who feel confident to take on the task themselves. If not, ask your mechanic to check it during your next oil change.

Monitoring and changing transmission fluid regularly can save you from a world of hurt in the long run. Indeed, most transmission problems stem from bad fluid. Keeping on top of this basic maintenance can prevent them from turning into bigger (and costlier) issues.

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