reply to ttiiggy
Re: Does it matter which way an automotive rear end turns?Yes, it would matter if done for an extended duration like you mentioned. For instance, a standard hypoid-gearset rear axle has a pinion gear that drives a ring gear against teeth that have a convex shape on the "drive side" and a concave shape on the "coast side".
Those shapes and the way they mate are designed to yield a quiet interaction, and long life. If you reversed that, you would have a noisier result, and shorter life, for the same reason.
Also most rear drive axles have oiling passages that depend on the lubricant being "slung" off the top of the ring gear toward the front of the case over the pinion shaft providing lubrication to the shaft and bearings. You would in not too long of a time starve the pinion bearing of lubricant, which of course is a fatal event...
Transmissions would also have similar issues, as the planetary gearsets within them are also designed with helical-cut gears that have a desired "drive side" versus the other.