The chart shows gear number, gear ratio, total ratio (including final-drive ratio), top speed in each gear, engine rpm at 5 mph and engine rpm at 75 mph. Math was involved.

With a First gear ratio of 5.94:1, I’d have big-time crawlability as well as the grunt to get going no matter what the grade/weight of trailer/load. The Sixth gear ratio of 0.74:1 would help ...

Again, the overall first-gear ratio with the TH400 and 4.10:1 rear gear would be 10.168:1. But 10.168 / 4.70 (to determine the equivalent rear-gear ratio) equals 2.16:1, which is not realistic.

After selecting the gear ratio from the chart, Brian at 4Wheel Parts replaced the factory 3.73 ratio with a 4.56 ring and pinion and the Tacoma was brought back to life.