4x4 not engaging

[Jack]

First off, I am not a mechanic, and barely know enough to be dangerous.
I have a 2002 f350 4x4 7.3 The 4x4 wont engage. It has a switch to turn it on. Lights go on when switch is turned on for both 4 high and low. I don't hear the click when I turn it to 4 high. I do hear it click in 4low. However, the front wheels don't engage in either. I just found that one hub will not turn from free to lock. The other will. I would appreciate any advice that I can get. Please remember I am a novice. Just a point in the right direction would help.

 

[Truckin4life]

switch on the dash?
possible vac leak, as the hubs are engaged by vacuum, the click could possible be the transfer case engaging... But its hard to say, do you know where the click is at? The hubs or the transfer case?

 

[d-kuzmen]

The most common cause of this concern is a vac leak to the hubs, or a oring/seal has failed at one of the knuckles. On way to check is disconnect the vac line from knuckles and use a vaccum pump, each knuckly should be able to hold vaccum. if one doesn't thats the side thats giving you an issue. As for the frozen wheel hub lock, very common, you can either attempt to repair or just replace the hub, pop the hub cap and there is a snapring holding it in sometime a few taps of a hammer is nessesary to remove it. An easy way to check the 4x4 is to put it in high and have someone move the truck while your watching for the front drive shaft to turn if it turns you know for sure theres a problem with the hubs.

 

[Larry B]

I started working on my 01 this morning for the same prob. It is real common for the vack line at the nuckles to crack where it hooks to the wheel. Mine was hooked up and looked good but cracked and loosing vacum at that point. The vack pump is under the hood over the right front wheel on mine. I expect on 02 also. You can turn the key on with out starting the motor and hear it run. It should pull vacum then shut off. It also runs the heater controlls. I am told if you have no vacume the defrost is the only thing that will work. Maby this will help