Vehicles’ vital fluids normally perform two important functions: lubricating and cleaning. As the fluid circulates through the parts, it gathers the dirt and metal shavings that can accumulate over time. If you’re lucky, this debris will settle on the bottom of the pan or housing and not circulate through the system.
That’s why some auto shops use machines that perform a transmission fluid flush, ensuring that more of this debris is removed before any new transmission fluid is poured into the vehicle. Nothing prolongs vehicle life more than regular fluid changes.
In automatic transmissions/transaxles, the recommended service interval is about every 30,000 miles or 30 months. (Check your owner’s manual or service manual for your car’s specifics.) The automatic transmission fluid (ATF) should be changed sooner if its dipstick reveals dark or burnt-smelling fluid.
What is Transmission Fluid?
Transmission fluid helps lubricate, cool, and clean internal components of the transmission. It also helps maintain the hydraulic pressure necessary for the transmission to function properly.
If you have an automatic transmission, it also acts as a coolant while also helping transfer engine power to your transmission.
Just like your engine oil, over time, the transmission fluid will deteriorate. As it becomes dirty and clogged with debris, it’s ability to keep your transmission lubricated and help transfer power will be compromised. Changing your transmission fluid is an economical way to keep your systems at the top of their game and avoid complex, costly repairs.
Why Does the Transmission Fluid Need to Be Changed?
It mostly comes down to heat. Heat is the biggest killer of your transmission, partly because it’s the biggest killer of your transmission fluid. The fluid is not only a lubricant, but it also serves to prevent corrosion and actuate the clutches inside the transmission that perform the shifts. When heat breaks down the fluid, it loses some of its capabilities.
Excess heat can be generated by stop-and-go driving, hauling heavy loads or towing a trailer. For vehicles operating under “severe service” conditions, you should probably have the transmission fluid changed more often — as might be called for in the maintenance schedule. Also, the clutch surfaces wear over time, and that creates debris. That debris is largely trapped by a filter that’s replaced when the fluid is changed.
Furthermore, it’s possible that the fluid level can get low, which can cause shifting problems. However, if the fluid is low, it’s likely because it’s leaking out somewhere, as it doesn’t just “burn off” as engine oil sometimes does. You can usually tell if the transmission fluid is leaking, as you’ll see pink or red puddles on the ground — or maybe dark puddles if the transmission fluid is bad.
In any case, a transmission-fluid change, if done correctly, can address all of those issues.
Transmission Fluid Change: Step by Step Guide
Different vehicle designs will have processes that depart from these steps. However, the following is a general guide on how to change the transmission fluid.
#1. Lift Your Vehicle.
Use a jack or ramps and raise the vehicle according to the manufacturer’s recommended lift points, or drive onto the ramps. Set your parking brake.
#2. Find The Transmission Pan And Set Up.
Locate the transmission’s oil pan and place a drain pan to catch the old transmission fluid.
#3. Drain Fluid.
Some transmission pans will have a drain bolt, which saves a lot of trouble. Others, you will need to loosen the pan bolts that will begin draining the old transmission fluid, and eventually, the pouring of the fluid out around the edge of the pan. Beware, the old fluid may be hot, and the more you loosen the bolts, the faster it begins to flow.
#4. Inspect The Transmission Pan.
Take the transmission pan and inspect carefully. Many pans will have a provision with a magnet stuck to it on the inside, to gather small metal particles in the fluid. Don’t be alarmed by metallic “gunk” on the magnet.
This is very normal from general wear, but large metallic chunks are not normal. Clean the pan with degreaser or in a parts washer, and wipe dry.
#5. Replace The Pan Gasket.
Replace the transmission pan gasket and filter being sure to carefully follow the filter replacement and proper gasket placement. Many use RTV sealant instead of a gasket, and you need to ensure that both sealing surfaces are spotless for it to seal properly.
#6. Re-install the Pan And Secure The Bolts.
After installing the pan, tighten the pan bolts to the recommended torque.
#7. Add Fluid.
Fill your transmission through the dipstick hole with a funnel and leave about a ½ quart of fluid in your last bottle. Some transmissions will have a separate fill hole, but this is rare.
Some vehicles, like Land Rovers, do not have a dipstick or fill hole up top, and a fluid extractor must be used to fill. Again, the owner’s manual and online will give you the best advice here.
#8. Start The Vehicle And Shift.
You’ll now start the vehicle, and take the vehicle into drive, then up to reverse, and back to park, waiting about two seconds in each spot. Repeat this process a few times.
#9. Check The Fluid Level.
Now, remove the dipstick and check the fluid level. Add the additional ½ quart of fluid if needed. Once your fluid is at the desired level, repeat step 8 one additional time, to make sure that fluid has circulated through all the circuits properly, and re-check.
#10. Check Your Work.
Lastly, with the vehicle running, check underneath for any drips or leaks. Test drive the vehicle.
When Do I Need to Change my Transmission Fluid?
It’s important to change your transmission fluid, but the type of transmission you have affects your ideal changing interval. If you drive manual, most manufacturers will recommend changing your transmission fluid every 30,000 to 60,000 miles. If you have automatic, you can typically boost that range up to 60,000 to 100,000 miles.
There’s no harm in changing your fluid early. Drivers will manual transmissions who put heavy-duty use into their vehicles may want to change their fluid every 15,000 miles. Likewise, changing your automatic transmission fluid every 30,000 miles may be necessary under some circumstances.
However, since the transmission is so important for your vehicle, you should also be aware of some common warning signs, including:
- Delayed engagement
- Slipping
- Burning smell
- Strange noises
- Leaking fluid
- Check engine light illuminated
If you run into any of these issues, bring your vehicle in for a transmission service as soon as possible.
Transmission Fluid Change Cost
The cost of a transmission fluid change, typically ranging from $100.00 to $300.00, is tied to the specific fluid required by the vehicle. Quality, brand, and quantity contribute more to the cost than labor.
Replacing your transmission fluid can be relatively inexpensive, depending on your vehicle type and whether you do it yourself or have it done by a professional.
For manual transmissions, you can get away with spending as low as $150, as no filter needs replacement. However, for automatic transmissions, the average cost can range from $80 to $250, and the average cost is around $100.
If you have the fluid flushed and the filter replaced, the cost can increase to between $230 and $475. It is best to get the filter replaced, and the pan cleaned every time the fluid is changed, as this will help your transmission last longer and avoid costly damage to your vehicle.