My quick calculations: With a stock .89 4th gear, a 4.12 ring & pinion with stock size tires (27 1/4" diameter) and no redux boxes a bus would be traveling at 88.57 mph at 4,000 rpms. Of course I will defer to engineer Will to check my calculations. Denis probably has slightly smaller tires and the answer would be a little slower; but it's still to *)(^&(&^%$ fast for a bus.