The RX300 debuted in the 1999 model year, as Lexus's first SUV. The RX300 lasted through the 2004 model year. Then, Lexus increased the SUV's engine displacement from 3.0 liters to 3.3 liters, and changed the name to the RX330. The 2000 RX300 had only one transmission available, a four-speed automatic. Lexus recommended inspecting the transmission fluid every 30,000 miles and replacing it at least every 120,000 miles. Lexus makes replacing the 2000 RX300's transmission fluid easier, by fitting the transmission pan with a drain plug.
Raise the front of the RX300, using a floor jack. Slide jack stands under the Lexus's frame rails, and lower the SUV onto the jack stands.
Crawl beneath the vehicle until you reach the transmission pan -- the metal pan on the bottom of the transmission. Position a drain pan under the transmission drain plug on the passenger's side of the transmission pan.
Loosen the transmission drain plug, using a ratchet and hex-bit socket. Remove the transmission drain plug by hand, and allow all of the oil to drain from the pan until only slow drips of fluid comes from the transmission pan.
Remove the transmission drain pan bolts, using a ratchet, socket and 6-inch extension. Pull the transmission pan from the bottom of the transmission. If the pan sticks to the transmission, lightly tap the side of the pan with a rubber mallet to free it. Pull the transmission gasket from the transmission pan.
Clean the gasket mating surfaces on the transmission pan and the transmission, using a plastic gasket scraper. Wipe the mating surfaces off with a clean, lint-free cloth.
Pull the magnet from inside the transmission pan and clean the magnet. Clean the inside of the transmission pan and the pan magnet, using a clean, lint-free cloth. Set the magnet back in place inside the transmission pan.
Apply a thin bead of RTV silicone to the gasket mating surface on the transmission pan and set the gasket on the transmission pan -- make certain to line up the bolt holes on the gasket with those on the transmission pan.
Remove the bolt securing the transmission filter to the bottom of the transmission, using a ratchet and socket. Pull the transmission filter from the transmission. Press a new transmission filter back onto the bottom of the transmission and tighten its retaining bolt to 8 foot-pounds, using a torque wrench and socket.
Place the transmission pan back onto the bottom of the transmission, and hand-tighten the pan-retaining bolts. Tighten the pan-retaining bolts to 6 foot-pounds, in a crisscross pattern, using a torque wrench, 6-inch extension and a socket. Do not over-tighten.
Hand-tighten the transmission drain plug into the transmission pan, and tighten it to 36 foot-pounds, using a torque wrench and hex-bit socket.
Raise the RX300 off the jack stands, using a floor jack, and remove the jack stands. Lower the vehicle to the ground.
Open the Lexus's hood and pull the transmission dipstick from the engine compartment. Insert a funnel into the transmission dipstick tube and pour Toyota Type-IV transmission fluid through the funnel -- 3.3 qts. in a front-wheel-drive RX300 and 4.1 qts. in an all-wheel-drive version.
Remove the funnel and start the RX300's engine. While holding the brake pedal, shift the SUV through all of its gears to circulate the fluid through the transmission. Put the transmission back into "Park."
Wipe the transmission oil off the dipstick, using a clean, lint-free cloth, and insert it into the dipstick tube. Remove the dipstick and verify that the oil level is within the "Cold" range on the dipstick. Add more Toyota Type-IV transmission fluid, if needed. Close the RX300's hood.
Drive the RX300 until it reaches operating temperature -- about halfway up the temperature gauge. Open the RX300's hood, and remove the transmission dipstick. Wipe the oil off the transmission dipstick, and reinsert the dipstick. Pull the dipstick from the engine compartment and verify the oil level is within the "Hot" range on the dipstick. Insert a funnel into the transmission dipstick tube and add Toyota Type-IV transmission fluid, if needed. Reinsert the dipstick and close the RX300's hood once the transmission is full.
Insert a funnel into an empty transmission fluid bottle and fill the bottle with fluid from the drain pan. Once full, close the bottle's cap. Repeat this step until you transfer all of the old fluid into the empty transmission bottles.
Take the bottles of old fluid and transmission filter to a used automotive oil-recycling center for disposal. Many auto parts stores take old fluid free of charge.
