I think some people here are not familiar with the Ford xx10 series. On my '85 1510, which is practically functionally identical to the 1710, the shuttle shift is not only F-N-R, but it's 1-2-3-N-R, so in reality, yes, you can indeed shift on the fly. Just a light press on the clutch, slip it in and go. Don't force it, just let it slip in. Your range selector on the floor (1-2-3-4) needs to be shifted at a complete stop, as is changing direction between forward and reverse, but you can, with a little practice, slip fairly seamlessly between 1-2-3 on the fly. The owner's manual backs this up.