Time: 45 min - 1hr

Difficulty: moderate

Cost: $100-250

FUNCTION

An automatic transmission is a complex hydraulic pump with gears, clutches, bearings, valves, and actuators. The fluid in an automatic transmission is used to apply pressure, transfer torque, clean, cool, lubricate, and activate components. To perform its function, it needs to be in peak condition.

WHY SERVICE

Replacing the filter and fluid often can prevent one of the costliest repairs you can experience on a vehicle, the transmission. Heat, shearing forces, contaminates, and wear cause automatic transmission fluid to lose its protective properties. As the fluid additives and properties break down, temperatures increase, clutches wear, flow restricts, and components fail.

INTERVAL

The transmission fluid and filter should be replaced on-condition, but industry standard is anywhere from 30-60,000 miles, depending on driving conditions. Heavy start/stop traffic, hills, towing, extreme temperatures, etc warrant earlier service, while long-distance flat-driving can stretch out the interval.

What does on-condition mean? New fluid is pink/red and opaque. Spent fluid is brown to black and has a horrible burnt smell. You obviously want to replace it before it gets to that point.

METHOD

Drop the pan, replace the filter, install the pan, and add the appropriate fluid amount. Ideally, you would then proceed into a complete transmission fluid exchange. If not, start the vehicle and set the fluid level accordingly.

The video below shows the fluid exchange on a 2009-2013 era Toyota Corolla.