I have a 2000 ford excursion (aka ford subdivision). It won't go into 4x4 hi or low. The transfer case motor is new and confirmed working fine. All relays were working fine and all electronics had no problems. When the car was brought into a heated garage to work on it, the 4x4 just started working after about an hour. Once it left and sat outside for a while, it stopped. I decided it was my hubs or vacuum system so I changed out the hubs to warn manul hubs instead of dealing with crappy ford vacuum systems. Still, it does nothing when I try to put it in 4x4. My main question is, does does the vacuum system keep the transfer case motor from switching to 4x4 until the vacuum system is happy? If I have a hub lock solenoid that is bad, will it keep the transfer case motor from operating? I checked the vacuum lines at the wheels and don't seem to get any vacuum when the selector is switched. I thought manul hubs were to skip the retarded vacuum system, but has Ford built in a vacuum system kill switch for the motor? Any help would be greatly appreciated.

 

If you have manual hubs and turn them to lock then that part of the 4x4 system is handled. You can confirm they are locked by reaching in behind the wheel and firmly rotate the inner axle at the ujoint.

When your are parked with the hubs locked you will not be able to turn the axle shaft. With them in free the will turn with some effort.

Sounds to me like somebody changed the fluid in your transfer case and used 90w instead of ATF which makes it difficult to impossible to shift when cold

 

Yes, I thought about the 90w in the transfer case. I haven't checked it but I have had the car for 4 years in Alaska and have never had an issue. It's always gone in right away and all of a sudden, about 3 weeks ago, it stopped cold turkey. It did happen to get cold at the same time with nights to -5, but nothing we haven't seen before. The manual hubs are locking in. I just don't get a 4x4 light on the dash when I select it, and it definitely is not in. When I talked to the mechanic (who checked out the system in his heated garage and could find no defects) I asked why, if it's just the hub/vacuum issue, can't I override that with the manual selection on the previous automatic hubs. (I tried that before I took it in to the shop to rule out vacuum issues). He seemed to vaguely imply the vacuum system prevents the transfer case motor from getting power unless the vacuum system said the hubs are in 4x4. But he was vague like he really didn't know. Then again, why go to a manual hub if the auto ones operated just like a manual set also?

How I long for the days of a mechanical lever. Simple, lasts forever, works flawlessly, cheap to own. I think the last reason is why it's a thing of the past:-(

On a positive note, it's supposed to warm up this week so I can see if it starts working again.

 

Your mechanic doesn't know the system. The light on the dash is only concerned with the transfer case locking into whatever you select and has nothing to do with what the hubs are doing. It is electric, so vacuum doesn't affect the transfer case at all. You have an electrical issue. You mentioned sitting outside for a period of time, does your windshield have a slow leak by chance?

 

I don't know of any leak in the window. I have never seen any water on the dash. My wife drives it most of the time, but she has never mentioned any water issues.

If it's just electric and not vacuum related, it seems I need to verify it's not a transfer case issue. Can I bypass the electric system and power the motor on the transfer case to verify it can move? I have put my hand on the motor while the switch is selected and I couldn't feel any vibration like the electric motor was trying to move and couldn't. I know I can't run the motor off the transfer case. Their was an explicit warning to not operate the motor when not on the transfer case because of damage to the motor. I don't have a wiring diagram for the motor so I don't want to jump things ***** Nilly. It has a six pin connector to a sensor/controller on the side and a two pin connector to the end of the motor. The two pin connector is labeled A and B. I pulled that connector and could not get any voltage from either pin when the switch was moved.

 

I do know you can take the motor off the transfer case and manually move the transfer case shaft into 4x4. I had to do that on one of my trucks when the GEM module died. Thats why I asked about the windshield leaking, it drips right on the GEM when it leaks and 4x4 seems to be one of the first functions it looses. I hope that isn't your issue. I believe the tech stickies here have instructions on how to check the switch in the dash (all your fuses are good right) but I am on my phone right now so searching is a bit tedious. I would verify the switch has the correct output, then figure out the pins on the tcase motor and power it off the truck. Even if you only blip it to verify that it works, I can't see that causing damage. Other than that, I think there are a few relays under the hood that send it in either direction. Then you are left with wires.