Instead of shifting at a certain rpm...... couldnt you shift at a certain mph? Im asking this because my tach doesnt work. And I prob wont be able to fix it for a while. And I want to go to the track again soon, but I wanna see if shifting at maybe a certain mph would help me out? Instead of just taking it to the end of each gear. If so, what mph in 1st, 2nd should I shift at? Thanks.