Thanks in advance for the help.

I have a 08 f350 power stroke with the electric switched 4x4. I hadnt used it in a few months, got stuck and turned it on. Still stuck, called a buddy. Then realized the front tires werent engaged. Manully locked front hubs and it worked.

Started trouble shooting. The vaccum pump by the cab. Disconnect hose, cover hole with finger, shuts off.

Traced line to some small electrical unit on passenger side, up top by radiator. Have suction there. Cover line with finger and vaccum motor shuts off. What is this part with the electrical connection and line in and out?

I then disconnected the lines on the hubs one at a time. No suction with vaccum motor running on either side. Should there be?

I then found out if i lock the hubs manually, and switch is in 2wd position, the 4x4 doesnt work. It doesnt work in high position either. It only works with hubs manually locked and swith in low position. Is this normal? How should it work with manual operation?


Any advice on where to look next, what to try, or what might be wrong?


Also, the swith does work i believe. In all three positions it moves a lever on the side of the transfer case. I have checked all fuses. Still need to double check them.

Thank you!

 

So a correction, when manually locked it works in high or low.

I have read a lot of old posts but havent found what i was looking for,most i found were for pre 2008 trucks and i dont know what applies.

I traced the lines coming from vaccum pump to whati think is a solenoid. Vaccum enters but doesnt leave. The leaving line goes straight to a T which goes to each hub. No suction at T or hubs.

What i think is the solenoid is located up top to the left of the power stroke logo fan shroud.

Could this be the problem?