No 4x4

[daveosok]

My 4 wheel drive just went out. My problem is listed above where the ac comes on but goes to the defrost. The 4x4 light is on but no 4 wheel drive. All other positions on the air controller work just when ever I put it in 4x4 it doesnt work and the defrost kicks on. Where would the most likely vacuum leak be at?

[daveosok]

Update
Left hub will not go from auto to lock manually. Right hub will. Put truck in lo 4x4 and 4 wheel drive works, hi 4 wheel drive works too. Suspect left hub problem dirty needs cleaning etc. No vacuum leak check lines good vacuum.

[daveosok]

Final update might want to check your hubs. My left hub needed to be cleaned and then lubed. Both hubs were lubed and now 4x4 works fine. Could be as easy as that and the cost is a lot cheaper than the 400 dollar estimate the Ford dealer gave me to trouble shoot the 4 wheel drive system.

[joemcmillen]

Daveosok,

Your prognosis doesn't make sense. If your A/C went to defrost when the 4WD was engaged, then you have a vacuum leak. If it wasn't the 4WD vacuum control system then the A/C would go to defrost all the time regardless if the 4WD was engaged. That would mean that the vacuum leak was somewhere else.

My experience was to check with a vacuum pump at both front spindles. If they hold vacuum then check at the control solenoid that is just behind the passenger side battery. I remove the vacuum signal hose (to the spindles) and connect a vacuum gauge to the solenoid and with the truck running engage the 4WD. The gauge should show signal. If it does, then the leak is between the soleniod and the spindles.

Hope this helps!

Joe