I have checked the vacuum lines and they are fine. Its electronic and when I turn the switch, the light on the dash doesnt come on and the transfer case doesnt engage.
My mechanical ability with electronics is limited so I would like some help figuring this out. I checked all fuses and they are fine. What else could be afoot here?
Oh, this is on a 2003 f350 6.0.

 

Have you checked it for codes Clay?

 

Yes sire, I have. Nothing related to the transfer case/transmission.

 

Lift the front end of the ground. Disconnect your vacuum hose at the hub and attach a vacuum line and manually apply a vacuum and see if the hub engages to the axle. If it does the issue is upstream, if not, the issue is in the hub itself.

 

I replaced the hubs with manual lockers last spring. If I lock them in, I still dont have 4x4. So I assume its the transfer case not engaging?

 

Is there a solenoid on the transfer case that could be not working?

 

When you lock your hubs with the front end off the ground and you turn the wheels, does the driveshaft turn from the front diff to the transfer case? Did they work after you installed them earlier?

 

I'll have to try that and see.
I honestly dont know when it quit working. I changes the hubs last spring because they were making noise and the bearings were out on one side so I changed them both.

 

I'm not 4x4 knowledgeable but IIRC there's a motor or solenoid on the xfer case, yes.

 

I think I'll find it and test it with a VOM If I can unplug it I can check for resistance and then check for 12v with the switch on.

 

There are two harnesses on the transfer case, I have the same set up as you, switch on the dash, manual hubs. The first harness plugs into a solenoid on the bottom of the transfer case facing the passenger side, can't miss that one, and the other harness branches off of that one and plugs into the top drivers side of the transfer case. Both plug in horizontally.

I had a very similar problem with my 4 wheel drive not engaging and no dash light. My problem ended. up being a broken ear on the top driver's side harness plug. Which caused a loose connection. So I unplugged both harness connections sprayed with electronics cleaner, and let them dry. Started the truck, engaged the 4 wheel drive on the dash, ( still no light ) crawled back under the truck, plugged the bottom solenoid back in, ( still nothing ) then the top drivers side. The transfer case engaged, (kind of scared me) so I let go of the plug and the 4 wheel drive disengaged. I reinstalled the plug and added a few small zip-ties to hold the plug on tight. ( since one of the ears were broken off ) and viola, 4 wheel drive worked again, its been that way for 3 1/2 years, still works fine.

It could be this simple, hope it helps, let us know.

 

Thats exactly what I needed to hear. Thanks! I'll look at it this weekend when I have it on the lift to fix my air horns.

 

Gotta have air horns Clay...

 

I know, right!

 

Gawd don't I wish. You don't even KNOW how many times my road rage self has wished I had some K5's