[jbrizz]

If you have onboard air you can just use 14.7 psi to push the diff lock to engage and it's the same as using vacuum to pull it engaged.

You could probably even use a few more psi to create a faster and more positive engagement.

 

[jbrizz]

Have you actually done this? The only info I’ve seen on converting the factory vacuum diff lock to air pressure involved machining internal parts for the actuator and that required removing the diff. Adding the expense of onboard air as well and reinforcing the vacuum lines just makes adding an electric vacuum pump a much easier choice in my view.

I've seen the a truck with it done, apparently worked fine, although not looked at how it all worked myself. I don't see how atmosphere on one side and vacuum on the other is different to 14.7 on one side and atmosphere on the other so I had no reason to doubt it.