This calculator has three useful tabs. Source data is a locked chart giving all of the gear ratios for the 924/944/951 series. 944 Gears is an unlocked chart using, as an example, an early 944 5th gear in a 951 box. S2 Gears is an unlocked chart using, as an example, a 944S2 5th gear in a 951 box. The calculator seems to be accurate within a couple hundred rpm probably based on the variation of tire sizes within the same size, i.e. a 275/40-17 Hoosier might be slightly different than a 275/40-17 Toyo

PorscheTrans1.xls