Since the truck originally had a 5.8L, I had to make this simple mod for the tach to work right with my 4.9L: just delete the ground (I pulled the terminal, but the wire could be cut) for the tach "8" input, and the tach will read 3 pulses as 1 rev, instead of 4.

It's possible that this wasn't necessary due to the engine harness' construction, but I wanted to be sure the tach was right.

Owner caption January 2012 · Photo 4187 of 5000