I have an 04 F-150, 5.4L, new body style. My 4WD will not got into gear, I found that the vacuum solenoid was not getting the ground sent to it when I turned the 4WD selector switch. I cut the ground wire going to plug on solenoid and wired it to the vehicle ground and I now have vacuum at both front wheels but the 4WD still won’t engage. Does anybody have any idea what the trouble can be? Is there a way to test the motor on the transfer case? I am getting no failure codes on my truck.

 

Did you check to make sure your actuators are good?

 

What do you mean by actuators? I replaced the 4WD vacuum actuator under the hood on the left side of the engine on the fire wall.

 

when you switch to 4 x 4, the FIRST thing that happens is the transfer case motor moves the shaft to engage the front drive shaft ( LO or HI gear for 4 x 4).. at the end of travel, a SWITCH IS ENGAGED for full stroke... THEN a SIGNAL is sent to the SOLENOID to get the front end to engage.... You have a problem at the SHIFT MOTOR, ... not the FRONT END VACUUM.

 

The IWE's default to engaged with NO vacuum - it's kinda a failsafe. IOW the truck has to be running and thus generating vacuum and the solenoid has to be engaged to UNlock the IWE's

So, with the truck OFF elevate the front wheels. You can lift one at a time if you want. Now try to spin each wheel, watching the CV shaft while doing so. If the shaft spins with the wheel, your IWE is engaged. Now start the vehicle in 2wd. After a few back and forth revolutions (to give the IWE enough time and wiggle-ability to disengage) if the wheel and CV shaft spin independently, that tells you the IWE is also capable of disengaging. Repeat with running in 4wd switch position - the IWE's should have vacuum removed by solenoid and revert to their naturally locked state, tying the front wheel and shaft together.

If all checks out, then that suggests your lack of 4wd is not in the front axle assy at all but rather the t-case.

 

Thanks for the info I’m going to work on my truck in a little bit.

 

There's also a sticky right at the top of the '04-08 forum for even further info:
https://www.ford-trucks.com/forums/8...then-some.html

 

This is what’s going on now. I pulled the motor off the transfer case and it was pointing half way between the 2WD and 4WD high. I left the motor off, put my truck in neutral and turned selector switch back to 2WD. I turned the shaft in the transfer case pointing it to line up with 2WD. I put the motor back on transfer case and pulled out into my road. I put my truck in park, moved the switch to 4WD high and drove around the block and pulled back in my driveway and left truck in 4H when I shut it off. I pulled motor back off of transfer case and it’s still halfway between 2WD and 4H. Does this mean my motor is bad and doesn’t have enough power to move the shaft where it needs to be or do I have a problem in the front drive shaft. I will say also that my 4WD has been used less than 50 times the entire life of my truck.

 

Ok, so can YOU get the t-case into 4wd? Maybe try rotating the front shaft as you attempt to shift it to allow everything to line up.

If YOU can do it by hand, it's unlikely the motor shouldn't also be able to get it there..

Those motors seize up if not used. It's really best practice to go for 4wd briefly whenever you're on a dirt road or whatever. Keeping everything moving actually helps rather than "preserving" anything as some people think (by trying to shift to 4wd as infrequently as possible)

 

It will not shift all the way into 4WD. The arrow indicator is halfway between 2WD and 4H. I also good vacuum at both of the front tires in 2WD.

 

I have my front end off the ground. I have my truck in 4H and the front driver side is locked in because when I spin the front driver wheel it turns the CV shaft on both sides but the front passenger side won’t lock in. I also try turning the front drive shaft coming out of the transfer case while the transmission is in neutral I can’t get it to turn. I thought of something and tried turning the front drive shaft and since it’s connected it’s trying to turn the rear shaft. Since the back wheels are on the ground I know why the shaft won’t turn. Should it turn with the wheels off the ground and the transmission in N? I also checked for vacuum at both front hubs while in 4H and there is NO vacuum.

 

Ok so it sounds to me like your right IWE is stuck disengaged.

N in the trans won't matter so long as your rear end is on the ground. The front and rear are tied together thru the t-case, so you're fighting the rear wheels, not the engine compression.

If you wanna verify just return to 2hi and you should then be able to spin the front d/s.

I'd only go with OEM IWEs. There's even a few Ford dealers who sell them on eBay. Here's a listing from Fairway Ford, as an example:
https://www.ebay.com/p/2292371455

 

Thanks for all of your help.

 

Don't vanish....let us know if you replace IWE and if it remedies the problem!

It's also not a bad idea to test the "good" one with a vacuum pump at the knuckle. If it leaks down much it's creating a vacuum leak and is on its way to a half engaged/half disengaged state that makes for some nasty clunks and bangs while driving.

Applying vacuum to the "bad" one theoretically shouldn't tell you much because vacuum only unlocks it and per your observations it's already stuck unlocked

 

I have to replace the upper and lower ball joints on both sides so I’m going to replace both of the IWE’s so I won’t have to worry about it later.