2005 4 wheel drive issues
 

I went to use 4 wheel drive today on my 2005 ford f-350 with the v-10, and it would not go into 4 wheel drive. so I got out and switched from auto to locked position on the hubs and it worked. so i switched it back to auto and it will not go into 4 wheel drive high, I can hear it switching or sounds like it is locking but just wont . So I tried 4 low in auto on the hubs and it works fine goes right in and out. Any Suggestions ?

This uses a vacuum hublock system. Check the vacuum lines from the frame to the spindels; they crack and leak all the time. If I understand this correctly, the auto doesn't work but they work fine when manually locked in?
These had a lot of problems with not working from the dash in auto, but manual would work fine. Most of the time, a very through visual inspection of the vacuum lines will reveal any obvious trouble. Another thing to check if the vacuum pump (they will run but not make vacuum) and the 4x4 switching relay, which is right next to the battery. This is what meters out the vacuum, and they have a history of problems.

that is correct the only thing is that 4 low works in auto .Where would the vaccum pump be .