So I was turning around in a mildly snowy parking lot yesterday and found out 4x4 doesnt work on my truck. the switch seems to work, at least the lights do, and it feels like 4lo is engaging in the rear end (more torque) or at least it seemed like it.
Its cold out, and my garage isn't insulated so rather than look the whole thing over I was wondering if there are common areas I could check first where the 4x4 vacuum lines break or other reasons why 4x4 wouldn't work? There arent any check 4x4 lights or anything like that on. No engine codes related to vacuum lines or 4x4 either

Truck is an 05 F150 Lariat 5.4L

 

Here you go:
https://www.f150forum.com/f72/how-di...m-esof-186872/

Whenever you can, get a vacuum pump and go through the troubleshooting steps. Good luck!