4x4 not working - Diesel Forum

bpathfinder · 11-05-2009, 07:18 PM

Just installed new vacuum pump and 4x4 still won't lock in. When I turn the switch on the dash it starts blowing out the defrost. Checked the switch on the firewall next to the pump and it started to blowing out the vent again but still not locking in when you put it in 4x4. Checked all fuses and they are good. 2005 F-250 6.0L Is there a motor on the trans. and would this cause this? Also switched hubs to manual and nothing happened.

gcoutlaw · 11-05-2009, 07:41 PM

You may want to see some of the other posts on this as I had a similar problem where my front hubs would not lock into 4x4 after switching into ESOF but I still could put it in 4x4 and manually set my hubs and they worked. I changed out to the WARM premium hubs and if I want to 4x4 I put them in lock and then switch the knob up front (I never needed ESOF anyway!). I just have to take the time to cap off my lines to stop the defrost issue.

durantdiesel · 11-06-2009, 04:34 AM

I just had this problem. We had to replace the relay and the vacuum switch on the fire wall. I put in a new shift motor and cab switch too before we found it was the relay. After we replaced the motor & cab switch still no go, this is when the tech found the bad relay, we replaced it now it would shift but not lock out the hubs so the vacuum pump on the fire wall was replaced and it all works good now. I would check your fuse in the cab to see if it has power to it. Mine did not so thats where the relay showed up. The tech said it got wet.

bismic · 11-06-2009, 07:13 AM

Edit - are your hubs not engaging or is it your transfer case that is not engaging?

If you have the defrost coming on when it shouldn't, you have a vacuum leak somewhere (behind the glove box, at a hub or two, or at the heater control valve)

bpathfinder · 11-08-2009, 04:55 PM

Friend of mine had the same problem with his 06 model. I replaced the relay on wall next to the pump Ford part #7C3Z-9H465-A on both of them and it fixed the problem. Dealership was the only place to get it. We paid $138.04 for two of them and I installed them. 8mm wrench and 10 minutes not bad