Good info, Dave! One other detail some folks forget, or don't know about in the first place is driven gear backlash, set by the thickness of gaskets and/or shims between the PTO housing and the transmission case. Too close, and the gears bottom out on each other, making shifting in and out of gear difficult or impossible, and causing rapid wear. Too much backlash (too many shims) and there's lots of slop between the teeth, resulting in noisy operation and/or gear tooth damage. There's usually an access hole to use a dial indicator to check the backlash.
Jerry
