Auto meter Gauges
http://www.autometer.com/media/2650-1563.pdf
if it's already here.. Sorry for the repost.
If your harness has a tach wire or you pinned one in and are using a factory tach, then when you have the PCM flashed you can have it set to 6cyl tach signal. If your truck had a 4cyl no change to the pcm program needed. LS engines send a 4cyl signal NOT V8 unless changed in programming.
Aftermarket tachs have a 4,6,8 cyl switch to change the signal, which you would set to 4cyl. A resistor is need on some tachs to boost the tach signal.
My 05 L33 required the 1/2 1k ohm resistor to boost signal to my sunpro tach. If this doesn't help you let me know.
http://www.hptuners.com/forum/showth...der-tachometer
http://www.hptuners.com/forum/showth...der-tachometer

