Changing the transmission fluid on an MR2 (MK3) is quite easy and should take 30 minutes to one hour.
- 12mm socket (speedo cable hole).
- 24mm socket (15/16 inch) (this is a big one that you probably don’t have. Borrow or buy.)
- Pan to collect oil.
- Channel locks or similar pliers.
- Oil – There is lots of discussion on oil, but it all comes down to using some form of GL-4 and not GL-5. Some have used GL-5 oils and heard a wine from the trans. The best choice is either Redline MT90 or Amsoil 75w90. Buy two quarts.
1.) Using the 24mm (15/16 in.) socket, open the drain hole closest to the bottom and drivers side of the car and drain out the fluid. You should get around 2 quarts. Replace the plug.
2.) On the top of the transmission by the exhaust, there is a “speedo” cable cover that can be removed to add the oil. Our cars don’t use this for the speedo but others models do. This cover “wiggles” out. Don’t use a screwdriver to pry it out or you will break something; use channel locks. It is tight but wiggles out easily.
Speedo cap in the wild:
Peeking inside after the drain. Hopefully no metal shavings here!
3.) Some folks just dump in 2 quarts of oil. Others open the drain plug below and fill until fluid comes out. There are several drain plugs on the trans. The one you are looking for is the one 1/2 way up the back of the transmission (towards the front of the car.) The oil does NOT fill up the transmission. It looks like it is about ½ way up or so.
4.) Replace “speedo” cover and drain plug.
5.) Waste oil can be taken to almost any auto parts store (Both Autozone and Advance take it).