Have suction, have spin, have NOT 4wd

Can't get power to my front tires. The front driveshaft is spinning. I rigged a vacuum line from the air compressor to the axle, so I have suction. For some reason still no magic. Help?

Have you opened up the housing and taken a look at the shift fork?

I had four break on me (even a cast iron one from a dodge d44).

ditto on the shift fork

You may have vacuum to the axle, but if the diaphragm is shot, it just leaks air without moving the shift fork - which is IMO the #1 reason most systems fail - engine oil contamination that deteriorates the rubber.

Once you unbolt the shift fork assembly, you can check it's operation, the integrity of the fork, and then decide if you'd like to just block it in the 4WD position (like late models - no shifter at all) - or change over to a mechanical cable. Then you can dump about 15 pounds of junk tubing and stuff that gets torn off wheeling anyway.

Sweet, I'll look at those. Thanks guys.
Vacuum cables hanging on an offroad vehicle always seemed a bad idea to me...