uhm. not that i dont believe you guys on shifting items in an auto yada yada.
but the actually shifting is done via transmission fluid. that has 0 to do with grounding.
the gates are controlled electronically yes, but by no means are they going to be able to tell a difference in -.00008 resistance and -.000009 ohm resistance.

i mean i guess i could be way off, but im not sure how many of you have rebuilt auto transmissions and are speaking from experience. or maybe you just want to feel good about the 150$ grounding kit.

now on a motor idling, sure, less resistance = smoother idle.