Well, I don't have anything to say for or against turning the engine off while shifting. I don't turn it off, but I also put it in 4-lo before I'm heading down, or up, a big hill, so it wouldn't roll even if I did turn the engine off and keep it in neutral. If you make the shift fast enough and in one motion, you should be fine and not get any grinding.

Mike
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'If a man speaks obscurely when he could speak more clearly, his words are to be interpreted against himself.' - Martin Luther