05- 6.0 automatic 4x4 won't work

[mtcarmelfarm]

Transfer case blowed up in my truck last year. I had a used on put in it. Every since I have to lock in my automatic hubs to get 4x4 to engage? Could it be wrong transfer case or another problem?

[NYC F-350]

Probably vac related.
The vac pump on the passenger side fender well area provides vac to the hubs, which locks them automatically.
Check the rubber hoses coming off the back of the knuckle and follow the line. Check it over carefully. You will probably find a split in there somewhere, or the vac pump may be dead.

Here is a pdf file for the whole system. It is for the 07 year, but I do not think anything changed between 05 and 07.

[mtcarmelfarm]

Thanks!!!!

[TxFireman1972]

Probably the solenoid on the passenger fender well. Fixed mine right up, it's like $50

[ak49er]

I just had a similar problem, it was simple, the large vent hose for the front differential had pulled off. This hose completes the vacuum circuit. I checked the hoses going to each hub, and then noticed the larger hose was just hanging from the frame rail.

Mine pulled off as it is a lifted truck with OEM length hose, and I hit some really big whoopee doos on the Alcan highway, probably what pulled it off the barb, I added a hose clamp after finding as much slack as I could.

Good Luck!