Looking for suggestions/advice on Arduino as transmission control module

mindforge:
wildbill, thanks for your concern - I'll do extensive testing with the wheels in the air

That won't do much good because there will be no load on the system. You need to test it on a rolling-road dynamometer. Or on private ground which the public is not entitled to access.

Have you got written approval for this from your automobile insurer? I doubt they will give it and most places you may not drive on a public road without valid automobile insurance.

...R