Transfer Case Issue?
 

Well, time to ask my first tech question. Anyways a few weeks back when I put the truck into 4H I waited a bit as usual before giving her some gas and when I did I heard a kind of a thunk like something was being forced into gear and I didn't really get any traction. This happened a couple of times and then it stopped happening. Tonight when I was out in the snow, I put it into 4H and noticed that the rear was swinging out on me which has never happened when it is in 4WD. This got me thinking that it wasn't really in 4WD and I noticed that the steering didn't feel like the front axle was engaged. So I'm thinking that for some reason the transfer case is not engaging. Does anyone have any ideas? Could it be a servo? Something worse?
To be honest I'm not really sure how these transfer cases work. Most of my experience is driving the older manual style where you manually shifted it into gear. I assume they basically work the same way except they use servos to do the shifting. Any help or advice is greatly appreciated.

I really wish there was an option for manual transfer case with manual hubs. I hate the 4x4 system on the truck.

Your transfer case is probably engaging just fine though. Likely, the problem is with the automatic vacuum actuated hubs or wheel ends.

When you turn the knob to 4x4, several things happen. An electromagnet (I believe) spins the front output shaft on the transfer case up to a speed matching the rear output shaft, then engages 4x4 when the speeds are equal. When that happens, a vacuum solenoid (IWE solenoid) on the firewall (behind the battery) stops applying vacuum to the integrated wheel ends (IWE). With no vacuum applied to the integrated wheel ends, a gear locks the hubs to the axleshaft.

So you can see there are many things to fail. If the 4x4 light comes on the transfer case should be engaged. The transfer case will not engage if there is not electrical power to the IWE solenoid on the firewall (at least mine doesn't). So assuming that 4x4 light is on, you probably have either a vacuum leak, a bad IWE solenoid, or a bad IWE. It could even be something as simple as water in the vacuum lines that has frozen and prevent vacuum from being applied to the IWE.

Due to the placement of the solenoid, when it rains, water can drip down from the firewall onto the solenoid. Ford released an updated solenoid with a little plastic hood to keep water off. See this thread for part numbers.

For reference, the auto hubs are LOCKED when vacuum is not applied. When the truck is off even in 2wd, you should NOT be able to turn the front axleshafts by hand. When you start the truck, they should unlock as vacuum is applied. You could start by confirming that this is happening.
When the truck is off, crawl under the front of the truck and verify that you can NOT turn either of the front CV joints by hand. Start the truck, crawl under and confirm that you can turn both by hand now. Turn the knob to 4x4, and confirm that they are again locked. Also keep in mind that, if one is locked, it will be tough (maybe impossible) to turn the other shaft. It might be easier to test with the front tires off the ground.

I hope that makes some sort of sense. It's late and I'm tired so it may not. lol

The hubs on my truck have been a little strange too. Although mine seems to have an intermittent problem where it stays engaged in 4x4 for a period of time, after shifting to 2wd. I guess that is the better problem to have, but still frustrating! I replaced the IWE solenoid and it seems to be less frequent, but it can still be stubborn when disengaging 4x4 when it's really cold for some reason.

Have you had your truck scanned for any codes? Some codes do trip a check engine light. That may help narrow down where to look. Could you tell about where the thunk came from? Was it in front or more centered on the truck? I would tend to lean more towards the hubs being the problem then the transfer case.

The check engine light isn't on, but I will run out with my code reader and do a scan to see if any codes pop up. Thanks for the info and the suggestions. I now have somewhere to start looking.

Problems with the hubs will not set off any codes, for what it's worth. The truck doesn't have a clue that the hubs aren't working.

That doesn't surprise me. Hopefully this weekend I will be able to get underneath her and see what's going on. Again thanks for everyone's help so far.

OK, so I was able to crawl under the truck today and if I understand Brian's explanation correctly, my issue lies with the driver's side IWE. When the truck is running and in 2WD, I can turn the CV joint on the passenger side but, not on the driver's side. When the truck is off or in 4WD I can't turn either of them. In your informed opinions would this be more indicative of a failure of the IWE or is it possible that it is just the vacuum line to that IWE? I think I still need to think this through to understand what's happening, but any comments or suggestions are welcome.

Have you had any noise from the front end in 2wd? Buzzing, whirring, something like that?

It sounds like that driver's side isn't disengaging, but I wonder why. It sounds like they are both engaging though...?

I guess the smart thing to do would be to look up a manual for diagnosing the vacuum setup. Typically I try to narrow something down and replace what I think it is, but sometimes that cost more money and aggravation. lol. So I hate to direct you to replace something that it may not be. I'll see if I can find some diagnosis stuff.

No noise. I agree it sounds like the drivers side is not disengaging. Which is kind of weird because as I said in my op when I turn, it doesn't feel like the half shafts are engaged at all. I have a Ford DVD with the factory repair manual so I've had a look at it. Tomorrow I will take my code reader out and see if any codes pop up and if so compare them to ones in the shop manual. If no codes pop, I'll have to think of something else.

Hmm. Often times they only partially disengage and the gears grind up in the wheel end causing the noise in 2wd.
However mine have been a little finicky the last couple months similar to yours. Originally I thought that maybe I had water in the vacuum lines that froze, but I don't know. Just a random guess on my part. I replaced the solenoid with the new part with a hood, but still don't really know if it that's the issue. Lately it has been working as it should.

I checked for codes this morning and none popped up. FYI, according to the factory manual any codes that popped up would be related to the 4X4 module(PCM). This may simply be because my scan tool is only really reading the OBD test that occurs when you turn on the key. If I understand the shop manual correctly, the Ford techs use their WDS which allows them to test specific systems and sub-systems. So for now I will take the fact that no codes showed as good news. I may just order and replace the solenoid because it is inexpensive and might work and at the very least I will have eliminated that as the cause. If I had somewhere out of the weather where I could crawl around and check the vacuum line I'd check that first.

Does anyone know if it is possible that this could be caused by low fluid in the transfer case?

I did this on my truck, and I know it's a lot older, but might help. https://www.f150-forums.com/1987-1996-ford-f150-16/how-change-transfer-case-oil-191/ You can pull the top fill plug and add a little if you suspect the level is low. But I don't feel this would cause your problem. I would still lean towards your hubs not engaging correctly.

I don't think it is either but it never hurts to check I guess. Originally I didn't think it was going from 4H to 4 L either, but I checked it again, and it seems that it might be. That is it feels like it is in a lower gear. I still don't feel the sluggishness in the steering that you would normally feel when the truck is in 4WD.

Again thanks for everyone's suggestions and help.

I installed the new solenoid and it kind of fixed things. The driver side hub is still locked, but by the condition of the fitting on the old solenoid the vacuum line is probably blocked. Once it warms up a bit I'll pull the lines off and check them out. I definitely have the 4WD working again. The street I live in is like a total sheet of ice right now, so I tried everything out and I had no traction problems when in 4WD. Almost couldn't move when it was in 2WD.

Anyways here is a picture of the old solenoid

http://i321.photobucket.com/albums/n...uchter/007.jpg

Gross dude! lol
Definitely need to pick check things out, get a vacuum gauge, etc. Mine was actually clean but it looks like you sucked something nasty up into there. Must have a broken line or....?

Good to hear you found it and the fix was easy enough.

So, it turns out that I am going to have to change the IWE on the drivers side. So I have checked both my factory manual on DVD and my Haynes manual and the place I can find where it talks about removing the IWE is as part of the half shaft removal. My question is for those of you who may have done this repair already is did you have to actually remove the half shaft or can the IWE be replaced without taking the half shaft right out?

I changed the IWE this morning and yup, it needed to be replace.

Once I got the wheel off and got the rotor and everything out of the way, I removed this

http://i321.photobucket.com/albums/n...hter/002-2.jpg

http://i321.photobucket.com/albums/n...hter/003-1.jpg

I was cleaning inside the hub and realized that I had not removed the complete IWE and removed this.

http://i321.photobucket.com/albums/n...hter/004-2.jpg

http://i321.photobucket.com/albums/n...uchter/005.jpg

So there you go. It was obviously like this for a long time. One more reason they should stop using so much salt on the road in the winter. Anyways here's a couple more of the two pieces fitted together.

http://i321.photobucket.com/albums/n...uchter/008.jpg
http://i321.photobucket.com/albums/n...uchter/009.jpg

Thanks for all the great info. I am having what I think is almost an identical issue to yours, however I am getting the grinding/whining noise while in 2WD. As I have already replaced the solenoid I think the bad solenoid either caused the IWE to go bad or a vaccuum leak. Do you by any chance have the procedure for changing the IWE's. I have looked at it with the wheel off and it doesn't look that hard but there are always some little nuiances. Any info you have would help.

4x4 keeps engaging and disengaging it pulses,