Lil'John

I did a search. Found LOTS of info but still was left confused.

My setup is a 2004 LQ4 from Silverado 2500HD with NV4500 transmission and a Haneline 3n1 speedometer cluster. I'm using the stock Silverado VSS to feed the PCM. I don't have a mechanical speedometer feed.

After the search, what I know is the following:
1) Green connector pin 20 (green/black wire) is vss lo input
2) Green connector pin 21 (purple/white wire) is vss hi input
3) Green connector pin 50 (green/white wire) is speedometer feed
4) The speedometer feed is a 4000ppm square wave signal
5) Some speedometers can use the 4000ppm square, some can't.

I've seen at least three recommendations and everyone who makes them claims they work and has at least one other guy confirm:
1) Tap into pin 21 to the speedo hi input, then tap into pin 20 to the speedo lo input
2) Tap into pin 21 to the speedo hi input, ground speedo lo to chassis
3) Connect pin 50 to the speedo hi input, ground speedo lo to chassis

What I didn't see answered is the following:
1) Can the PCM output of 4000 pulses be programmed different? I looked through my Jet DST but didn't see anything. OTOH, I'm realizing the thing is a POS
2) Does tapping into the factory VSS wiring have any potential of screwing up the signal to the PCM?
3) Is there a preferred place to tap into the VSS wiring? My mind says either as close to the VSS or PCM as possible.
4) What does the stock VSS output? I've read 8000 ppm sin wave signal.

Due to a cleaner wiring potential, I am partial to using pin 50 but I also don't want to screw things up. If I can get answers to my questions, I'll look smarter when I email the gauge company