hey all, im no stranger to putting a tach on a gas powered engine, but im kinda curious about putting one on a diesel. im lookin to put a small gas guage in the truck, and replacing the big gas guage with a tach. ive done a little searching and found mention of a optical pickup tach where you paint alternating black and white stripes on the harmonic balancer and position a optical pickup in order to measure rpms. my question would be, how does that work when you go mudding? or get water above fender level? has anyone setup something like that and had problems? ive also heard about magnetic pickups. which would probly work better, but i still have reservations about. are optical and magnetic pickup tach's the only option for a diesel owner who wants a tach?