Most all of the fastest 6-Speed Supras use the stock tranny and diff, with an upgraded clutch. There are SEVERAL 800+ RWHP SUpras that run the stock drive train. I thinks it's easy to say that the trannys can hold 1000HP fairly reliably. The Supra TT auto trannies are the only ones that need upgraded as far as I know. Someone please correct me if I'm wrong.