[davepl]

Just kind of wandered into this 275 post thread so forgive me if I don't have all the context, but from what I've gathered:

You have an ECM that needs a speed signal sensor. You have a TH350 trans that does not provide a digital speed signal.

So you're adding a VSS sensor that will provide the ECM with a pulsed signal. The ECM and the sender need to agree on how many pulses per revolution. Normally for a GM auto transmission it is 40 pulses per rev.

If, for whatever reason, the speed sensor you wind up using is a different number of pulses per revolution, you can change it in the LS3 computer if you have HPTuners or similar. Odds are you're going to have to edit it to change tire size and gear ratio anyway.

For example I bought the "automatic" LS3 that comes set up for 40 pulses per rev but then put it in front of a TKO-600 trans that is (I think) 17 pulses per mile so changed it in the ECM before I ever installed it.