Help Needed four wheel drive

[phipps]

I have a 2003 xlt 7.3 and the 4x4 switch dash seems to be not working fuses are good ,defrost and all is working fine looking for help on were to start?

 

[dboyw]

With a switch on the dash, I will guess you have the auto lock hubs. If so, most likely is you have a vacuum leak at the hubs, common problem. Quick check is to manually turn the hubs to lock. The axle is live now but not in 4x4. Go drive and switch to 4x4. This should still engage the transfer case. Do you have 4x4? If so, start looking for the vacuum leak. The hoses near the hubs are a likely culprit.

 

[phipps]

I tried locking manual hubs still nothing, when I turn switch to 4x4 the dash light dose not come on,i pulled dash out by switch and there is no power going to switch,fuses are good,i put new relay in under hood by airbox , vacuum pump is working,no problems with switching hvac?.. the light on dash works for a short time when starting , and there in nothing going on at transfer case

 

[DaveBen]

There is a shift motor in the transfer case that can go bad. If the motor is shot, no four wheel drive. I do not know how to test the motor other than putting +12v and seeing if it engages the gear for four wheel drive. You will hear it shift.

Dave

 

[JLDickmon]

I tried locking manual hubs still nothing, when I turn switch to 4x4 the dash light dose not come on,i pulled dash out by switch and there is no power going to switch,fuses are good,i put new relay in under hood by airbox , vacuum pump is working,no problems with switching hvac?.. the light on dash works for a short time when starting , and there in nothing going on at transfer case

there are two relays under the hood, at or near the main fuseblock that control the shift motor..

 

[RandyH]

Here's a thread on another site that has some pretty good info in it. Might help.

http://www.ford-trucks.com/forums/893984-f-250-super-duty-4x4-electronic-shift-on-the-fly-help.html