How to Replace Transmission Filter on 99 Lexus RX300

The 1999 Lexus RX300 is equipped with either a two-wheel-drive transmission (transaxle) or a four-wheel-drive transaxle and transfer case assembly. Replacing the transmission filter, fluid and gasket in your '99 Lexus will help prevent premature failure of the transmission and/or transfer case. Performing this project is the same in both versions and can be completed by the do-it-yourself mechanic in a couple of hours.

Things You'll Need

• Wheel chocks
• Floor jack
• Jack stands
• Drain pan
• 10 mm Allen wrench
• 1/4-inch drive socket set
• Screwdriver set
• Torque wrench
• Funnel
• Parts cleaner spray
• Scraper
• Gasket adhesive
• Transmission fluid
• Gasket and filter kit

Instructions

1. Apply the parking brake and set wheel chocks behind the rear wheels. Position a floor jack under the front sub-frame and lift the Lexus until enough clearance is provided for you to work comfortably underneath. Set jack stands under the vehicle and lower it onto the stands to support the weight.

2. Remove the 10 mm bolts that attach the plastic shield to the underside of the vehicle using a 10 mm socket and ratchet. Use a screwdriver to pry the two small plastic clips that hold the cover to the front air dam and slide the cover out from under the car.

3. Slide a drain pan under the car. Remove the drain plug in the bottom of the transmission pan, located in the right-front corner of the pan, using a 10 mm Allen wrench and drain the transmission fluid into the drain pan. Examine and clean the drain plug, then reinstall it in the pan when the fluid is completely drained. Tighten the drain plug to 36 ft-lbs. using a torque wrench.

4. Locate the transfer case drain plug, if equipped with AWD, and remove it with the 10 mm Allen wrench. The transfer case drain plug is located on the transfer case near the transmission drain plug. Approximately 1/2 quart of additional transmission fluid will drain out of the transfer case. Reinstall the drain plug and tighten it to 36 ft-lbs.

5. Remove the 10 mm bolts that attach the transmission pan to the transmission using a 10 mm socket, ratchet and short extension. Lower the pan to the ground and examine it for large pieces of debris that might indicate transmission damage. A small amount of gray slurry is normal, but pieces you can feel when rubbed between your fingers is not normal.

6. Clean the pan and transmission gasket surface with parts cleaner spray and a scraper until all traces of old gasket are removed. Apply a thin bead of gasket adhesive to the surface of the pan and stick the new transmission gasket to the pan.

7. Remove the three 10 mm bolts that attach the filter to the transmission, using a 10 mm socket and ratchet and remove the filter. Hold the filter with one hand as you remove the final bolt to prevent splashing fluid when the filter comes off.

8. Push the new filter into place, making sure not to pinch the sealing O-ring on the filter, and install the bolts. Tighten the bolts snugly. Position the transmission pan onto the transmission and install the bolts by hand. Tighten the bolts snugly using a 10 mm socket and ratchet, being careful not to crush the gasket by over-tightening.

9. Reinstall the plastic shield under the vehicle. Raise the Lexus off the jack stands with the floor jack and remove the stands. Lower the SUV to the ground slowly by releasing the jack.

10. Place the funnel in the dipstick tube under the hood and add 5 quarts of Lexus T-IV transmission fluid. Start the engine, shift the transmission through all the gear positions slowly, and then check the fluid level.