Your Nissan 240SX contains a transmission system entirely dependent upon fresh fluid in order to function properly. As transmission fluid becomes older, it thickens and is less effective as a cooling agent and lubricating base for the gears of your transmission. Without fresh fluid, the components of your transmission are likely to start chipping away due to the friction of shifting gears. To maintain fresh fluid in your 240SX's transmission, you should plan to change the fluid as part of a regular maintenance routine at approximately every 40,000 mile-mark.
Run your car's engine for 10 to 15 minutes. This warms the fluid so that it will drain more easily.
Park your 240SX on level ground and turn off the engine.
Elevate the car six to eight inches from the ground using a jack.
Place a jack stand next to each tire on the inner portion of the car's body.
Step back from the car to see if your 240SX is sitting evenly. A tipped car means that the transmission pan is also tipped, which can create a safety hazard during the fluid replacement.
Slide under the front of your car to find the transmission pan. The 240SX's transmission pan sits mounted near the driver's side floor and can be recognized by the many bolts attached to it, as well as a drain plug.
Set your drip pan under the transmission pan's plug.
Turn the drain plug counter-clockwise with your 17mm socket wrench until it releases and fluid begins to pour out into your drip pan.
Remove the transmission pan's bolts with your 17mm socket wrench after all of the fluid appears to have drained out.
Pour the old fluid from inside of the transmission pan into the drip pan.
Wash the transmission pan thoroughly by putting enough degreaser on your shop cloth to effectively clean the old fluid out.
Connect the transmission pan back into the same position it was in before you unbolted it.
Remove the jack stands so that you can lower your car with the jack.
Open your hood and find the fill port at the top of your transmission.
Disconnect the fill port cap by unscrewing it. Notice that the dipstick is attached to the cap and set this aside.
Lock the emergency brake all the way to the floor of your car.
Run your engine during the remainder of the fluid replacement process.
Place your funnel into the fill port's opening.
Pour the first 2 qts. of fluid into the fill port slowly.
Shift your car's transmission, holding each gear idle for at least five seconds. This ensures that the fluid will flow to each part of your transmission.
Place your dipstick into the fill port to check the fluid level after you have shifted into each gear of the transmission. If the fluid reaches the fill line on the dipstick, do not add more fluid. If the dipstick is not wet at the fill line yet, continue adding small amounts of the third quart of fluid until the dipstick's fill line is wet.
Close your hood, unlock the emergency brake and turn off your engine to complete the transmission fluid change in your 240SX.
