I have searched the great many pages here on 4WD problems but not found my specific issue. 2006 F150 with dash (electric) switch.

Simply enough it doesn't go into 4wd. Now that shows up many times in the archives but always with the comment that the dash light flickers or doesn't come on. My dash light comes on both for 4H and 4L, but no actual 4WD.

No associated sounds either, except a very slight click in the dashboard when I turn the switch, which I assume is a relay foe the light.

I just bought the truck from a low-lander and assume he never used the feature, which seems to indicate stuck electric motor outside the TC, but that line of research always says no light on dash. What's up?

 

If the light is coming on then the truck "thinks" it is in 4x4.

That leads me to look at the vacuum portion of the system.

 

I basically agree, but with a slight twist. Yes, it has to be in the IWE system somewhere. The system is designed so a failure in the vacuum will cause the hubs to engage, the idea being you'll still have 4wd available. The twist is that if the hubs (IWEs) were engaged you'd have 4wd working. My feeling is you have an IWE stuck open/disengaged, or possibly stripped.

 

If the IWE solenoid is not working it will not release vacuum or provide vacuum.. engage/disengage of the wheel ends. Test this first by pulling the vacuum line and see if the wheel ends engage.

 

Ironically I just saw your thread. And the problem you are describing seems to be the same problem I just posted a thread about. You might want to look at my thread and what I posted I think it could possibly help you figure out your problem.

good luck

Im still in the process of trying to figure out exactly what is wrong with my truck so I can fix it or have it fixed

take care

 

Actually a vacuum pump would help a lot for troubleshooting.. you just did it all the hard way but, it works

 

Yup, unusual but not unheard of for and IWE to fail open.

If one IWE is open then all the power will transfer to that side since there is no load and our trucks have an open differential in the front.

As tech rep noted, a vacuum tester will help properly diagnose the issue.

For me, it ended up being multiple issues that likely piled up over time. So test everything and do not assume the first problem will fix the issue.

At the very least, a vacuum tester will allow you to rule out the IWE system.

 

Well I did the front drive shaft test and it passed, the shaft spins free in 2WD and is locked in 4WD. So my understanding of the system means that the transfer case is operating correctly and the problem is on the vacuum side.

I guess my next test is to open the vacuum at the solenoid and see if the hubs engage.

Heavy storm here and I can't work on it steadily, so bit by bit...

 

OK I can now confirm that my vacuum solenoid is working.

But even when I pull the lines from it the hubs are still not engaging. Thoughts? As far as I understand the system there are no more components to be tested between the solenoid and the hubs, no check valves or anything.

 

How did you check to see if the IWEs are engaging?

IF you are correct that does not necessarily mean that the Solenoid is working. It may have in fact failed at some time and the IWE hubs are now locked from lack of use.

The only true test for a proper diagnosis is use of a vacuum tester. Go borrow one from your local autoparts store.

This will tell you for certain if the solenoid is working. It will also allow you to test both IWEs by themselves as well as testing the entire system for leaks from the line exiting the solenoid.

Do it right and save money in the long run