The transmission fluid in your 1998 Nissan Altima keeps the automatic transmission shifting smoothly. If your Altima is low on fluid, it's important to add enough fluid to bring it up to the recommended lever; however, precautions must be taken. Too much fluid is just as bad as too little fluid. The transmission fluid must be at operating temperature to properly determine the level.
Drive your Altima for approximately 15 minutes. This will bring the transmission fluid to operating temperature. The most accurate way to check your transmission fluid level is when the fluid is hot.
Park your Altima on level ground and set the parking brake. Apply the brake pedal and move the gearshift selector through all the settings (Reverse, Drive, 1 and 2). When finished, move the gearshift back to "Park" and leave the engine running. Open the hood.
Locate the dipstick (to the left of the battery) and remove it. Wipe the fluid level indicator clean with a dry shop towel. Fully re-insert the dipstick into the funnel, and then remove it again.
Examine the side of the level indicator labeled "Hot." The level indicated should be within the range of the perforations along the dipstick. If it's not, proceed to add enough fluid to bring it to the recommended level.
Insert a funnel into the dipstick tube. Add automatic transmission fluid in small increments, then check the level again. Repeat the process until the fluid level is between the perforated marks.
