The unloaded gate is the 3-4 gate. Just push forward and it will naturally go into the 3-4 gate. I learned this while testing Vipers at work. You almost don't want to think side ways....just forward.
Over a certain rpm and power the tko is impossible to get into 3 with out granny shifting. The carbon fiber syncro and brass shift tabs will help. Just sold my tko 600 due to this. Went a different route for now. The tranny was awesome when I only had 450 h.p. and was shifting at 5500 rpm.