I have had best results from Redline MT-90 (75W-90) or Amsoil MTG 75W-90, both dedicated GL-4 manual transmission gear lubes. Toyota usually allows for a GL-5 gear lube as well in their manual trans units, but I have had better shifting from the Redline or Amsoil dedicated lubes. Kind of expensive for an old trans, but very smooth if that's what you are looking for.