where does the vacuum hose start for the 4wd on a 2001 dodge 2500 diesel there is no vacuum

The vacuum supply line on my truck does not go to the line on the fire wall where else could it connect?

Speed sensor has nothing to do with vacuum. Speed sensor is located on top of gear housing on rear axle

And the vacuum line goes to the transfer case then back up to the front axle lockin

And if you have a vacuum line not connected you will have excessive crank case pressure/blow by that obviously works both ways if you have excessive blow by you could possibly have a vacuum leak