There are a huge number of threads discussing this on [=MR2OC=] forums. A brief summary follows.
- The MKI SC transmission uses fluid with a [=GL5=] rating; the NA uses [=GL4=].
- NA uses 2.7 quarts; SC uses 4.4 quarts (although not many get that much in there).
- MKI SC transmissions specified 75W-90 [=GL5=] oil, so they don’t have yellow metal synchronizers.
- MKI NA trannies specified 75W-90 [=GL4=] oil, so they don’t have yellow metal synchronizers.
- The drain plug is 24mm.
Either Redline [=MT-90=] (around $8 per quart, [=GL4=] rated) or fully synthetic [[http://www.pzlqs.com/Tech/Pdsheet/DomesticMarketing/Gear&Transmission/pdf/SyntheticSAE75W90GL-5.PDF | Penzoil Synchromesh]] ([=GLS=] rated (yes, that’s the letter S not number 5); around $5 per quart from [=AutoZone=] – look around, as the staff usually don’t know it exists).
Some excellent instructions are at http://www.turbomr2.com/MR2/HowTo/Maintenance/ChangeTransOil.htm. Make sure you loosen the fill plug ‘’‘before’‘’ you drain all the fluid out – otherwise if the fill plug turns out to be stuck, you’ll have to [[http://www.mr2sc.com/websites/tech/TransFluid/ChangeTransFluid.htm | fill from the bottom]].