Ah, it's time again to play my favorite gameshow, "What's Wrong With My Truck Today?", brought to you by the Ford Motor Company!

So, as the title states, my 4wd decided to be a no-show when an early winter snowstorm hit last week. Which wouldn't have been too bad, except that my truck handles like a pig on ice skates on snowy/icy roads in 2wd. With winter breathing down my neck and more weather on the way, I need to figure out the problem and get it working again as soon as possible, because a 2wd truck in Montana during the winter is teh sux. But in my experience with every problem I've had with this truck, nothing is ever a simple solution, so I want to make sure that I'm fully prepared before I start buying parts, only to remain without 4wd because of something else.

Here's what I know so far:

When I turn the **** to engage 4wd, the 4x4 light on my dash does turn on, and I can hear something mechanical from under the truck if I have my window down. I replaced my vacuum solenoid a couple of years ago with the upgraded "hooded" version as a preventative measure. I checked the vacuum lines coming from the hubs, and when 4wd is off, they have vacuum.

While the truck was still on the ground, my next step was to check the transfer case. I had my wife start the truck while I was underneath it (and she didn't take advantage of the chance to cash in on my life insurance policy, so at least my marriage is still good! ) and then had her engage/disengage the 4wd while I was under the transfer case to listen for whether it was engaging or not. I could audibly hear something moving and klunking into place when she activated the switch, but based on advice I had read, I had her continue to engage/disengage it while I tapped the case with a hammer. I didn't notice any change in the sounds I was hearing, and after I engaged 4wd and tested by making tight turns in a dirt parking lot, it was obvious that 4wd was still not happening. I don't know what the transfer case sounds like in terms of "normal" engaging sounds, but nothing sounded to my ears like there was a damaged component. The sounds of the case engaging/disengaging were consistently the same, just the soft whirring "klunk" sound of something moving into place against something else, but nothing grinding or making any other sound that I would associate with something damaged.

So the next step was to test the hubs. I jacked the truck's front wheels off the ground and tested them with the truck off. The driver's side was locked in and turned the front transaxle, but the passenger side did not. Ah ha! Problem solved, yes? Well... maybe not? Doing my due diligence, I turned the truck on, and tested both hubs again by spinning the wheels. Passenger side still spun freely, as expected, but the driver's side was still locked in. I did a quick bypass of the solenoid using a tip from Ford Tech Makuloko on YouTube, which would have applied constant vacuum to the system, but the hub still remained locked. I then took a vacuum pump from my brake bleeder and vacuum pump kit, and connected the pump to the line that supplies vacuum to the hubs. I pumped it up to 10psi, which should hav disengaged the hub, but it still remained locked in place. I noticed that the gauge on my pump also showed a drop of about 2-3 psi after I went to spin the driver's side wheel. I pumped it back up again to 10psi and waited a few minutes and saw that again, the pressure was slowly bleeding off. So I pumped it up to about 15psi, to see if there might be a slow leak in the hub that was preventing it from getting enough vacuum to disengage, and a higher level of vacuum pressure might be able to hold it in place just to see if it's still stuck in the locked position. I spun the tire, and once again, it did not spin freely, turning the transaxle with it. I tried to see if I could put my vacuum pump directly onto the hub's vacuum supply line, but unfortunately the only piece of tubing I had was just slightly bigger in diameter than the factory line, and wouldn't form a tight enough seal over vacuum connector on the hub. All I can say for sure is that the driver's side hub won't unlock, but the exact reason why is unknown, although I wouldn't rule out the possibility of corrosion build-up given the age of the truck and the fact that I've encountered and dealt with corrosion elsewhere.

So now by my count, I have one hub that won't lock in, and one hub that is always locked in, which means that both require replacement, correct?

The one other question I had was about how the 4wd works in the front wheels. Because I technically should have 3 wheel drive with the one hub that is always locked, and yet I have no traction from my front end when 4wd is engaged, I want to make sure I understand what/why I still lack any traction. As I understand things, the front end has an open differential, so when one tire is locked and the other is spinning freely, the differential is just putting power to the unlocked wheel because it has the least resistance, which means that I'm still getting jack-all for front end power. Am I correct in this assessment? I just want to be sure that when I finish replacing the hubs I won't find myself without 4wd because of yet another problem that I failed to diagnose because I didn't have the right understanding about how the system works.

If anyone has any input about anything I might have missed during my diagnosis, or just can affirm that my assessment of the problem is correct, I would greatly appreciate it. I'd like this to be a "do it once, do it right" kind of repair, instead of it being turned into some drawn-out struggle to try and find the other problems before the next winter storm hits.

 

one thing to check is when the transfer case engages the FRONT end, does the FRONT drive shaft turn ( same speed as the back driveshaft) so you have power TO the front pumpkin............. after that, it does sound like its time to look at the IWE at the wheel ends... you could also have a vacuum leak that would leave them engaged... not sure if a pressure test is a good replacement for a vacuum test


i think the sequence of events is ... you turn the ****... the transfer case motor rotates the shaft and engages the front drive shaft... as it turns FULL STROKE the motor hits a switch that closes and tells the solenoids on the fire wall to OPEN or CLOSE and allow the VACUUM to go to the front IWE, or shut it off and bleed........... If the transfer case motor does NOT GO FULL STROKE and hit the switch, then there is no signal sent to the front end.... i think the "FULL STROKE SWITCH" also turns the light on / off on the dash telling you about 4HI / 4LO / or 2wd.

 

You need replacement IWE's. The front diff is open so if one is locked you still will spin the axle thats unlocked.

 

Sounds like you already checked the IWE sticky on the front page of these forums and found the FTMUL videos, so here is my advice because I had the same issue - in Montana last month

I had to replace the solenoid and the whole vacuum lines then mine worked perfectly. If it were the IWE's themselves, you would hear a grinding noise while driving. I think even with a small leak there was enough vacuum to keep my front drivers side in 2wd, but the leak was on the passenger side and I know that one was locked. I did all the tests too and nothing added up. It was really odd.

The first thing I did was grab a new solenoid (after all the tests of course - and not seeing anything adding up). Get it from Amazon, not the FORD dealer. They gave me the old one and not the complete thing. I also grabbed the check valves (2 of them). That seemed to solve it, until I realized that during my testing I did not hook a vacuum line back up correctly and it wiggled free, rubbing my rim and creating a leak. I felt it the first day and that's when I replaced the lines. Well, that was "fun". But definitely worth it. I never trusted those old lines anyways.

Your problem sounds exactly like mine. Usually I do not advise to just start buying parts, but with such a weird system, that's exactly what I did. I knew I wanted to replace it all anyways to avoid future issues and possible small virtually undetectable leaks that might already exist. I say just get the new solenoid, lines, and check valves. I highly doubt it's the IWE's because you'd be driving with a chainsaw sound if it was. I had one of those fail early on and wow, that was a scary sound. Since you are jacking it up, check those hubs for play to be sure everything is okay. I replaced a front right hub too same time I did the lines because of slop.

Also, where in MT are you located?

Here are the parts:

 

Thanks for the replies!

Well, for sure my passenger hub is definitely in need of being replaced, because it doesn't lock at all, it's just always stuck in the unlocked position, whereas my driver's side hub is always locked. I do have the new style of vacuum solenoid with the hood on it, and while I don't have a vacuum gauge to test the amount of vacuum coming from it, it does provide vacuum and was doing the job at least the last time my 4wd worked. I ordered both hubs to replace, I figure I'll replace the passenger side first, since it's not locking out and obviously is in need of replacement. After that, I'll test the system again. If the passenger side unlocks when the vacuum system is engaged, then I'll know that the driver's side hub also needs to be replaced if the passenger side can unlock but the driver's side still won't.

If both hubs refuse to unlock, then I'll go through the trouble of replacing the vacuum lines since obviously the vacuum system is failing somewhere. I also ordered a new check valve for the system, but it sounds like I need more than one? I only recall seeing the one right by the solenoid, but I only ordered the replacement after seeing it listed as another suggested replacement part in the YouTube videos. It wasn't anything I was really looking at when I was troubleshooting my truck, so I didn't trace the lines any further looking for check valves, etc.

I agree, this is a weird system, and it's not easy to accurately check without specific tools like a vacuum gauge. And of course, in my experience, once this is fixed, it's just a matter of time before something else starts making a weird noise and/or stops working, and then I'll have to fix THAT too... I figure I've put at least another $3000, if not more, into this truck since I bought it 5 years ago. Ugh!

Oh, and I'm in Stevensville, just south of Missoula. What part of MT do you hail from, 3Prcntr?

 

Kalispell, and I have also put that much in to my truck, possibly more. I understand the frustration. I have not gone one year without dumping money into it. I got it at 130k and just hit 170k. The first year was the worst, but it really is one thing after another. Hey, it's running now though, lol. I forsee an AWD hybrid SUV variant in my future - and NOT a Subaru. Never a Subaru. I almost traded it for a 2020 Camry but then I woke up and realized how dumb that would have been. I see tons of FWD vehicles up here and I just wonder "why? and how?". Not even snow tires are enough. You need ground clearance and some dirt roads? Forget about it. City slickers... My truck has failed me multiple times, but it's like frankenstein and keeps coming back to life. Lesson learned though. I see tons of these year models on the road and some look to be in really good shape, but friends I know that have either owned or currently own them - all run into the same issues. Sad really. Seems like the best models are 08 FX4's and those with towing packages. Hit and miss really... and all the bad stuff comes out online, but dayum FORD... wth...

Let us know what you find and if it works.

 

Lol, I bought mine with 125k on the odometer, and I literally had my first repair the next day. The stupid starter had a seal failure or something, and moisture got inside and froze it solid when we hit subzero weather overnight. Thankfully the dealership where I got it paid for the part, I just had to do the labor to install it, and what a miserable installation that was. Trying to get the bolts off was a pain because there was so little room to get anything up inside the cavity where the starter is bolted in. It took me 10 minutes to screw one of the bolts in because of how limited the space was, I had to use the closed end of a box wrench because the amount of room wouldn't let me turn it so much as 1/4 of a turn before the wrench ran out of clearance. I'm sure plenty of mechanics have better tools for such ridiculously small spaces, but for those of us who are weekend warriors with our tools, it was not the most accommodating part to replace. I also rebuilt the timing system, and all I can say is that I really hope that any repairs on that are the next guy's problem, because I do NOT want to tear back into that engine a second time. It seems like it might be a fairly easy engine to work on if it's not inside the engine bay, but the way it's mounted in the truck just adds complications.

I almost considered maybe going with a good 4wd SUV, but I realized that I get way too much use out of having a truck to suddenly go without one. So for now, I'm just going to follow the adage that "The most affordable car you can have is the one you already own" and try to keep it on the road for another year or two.

Hubs just got delivered today, but the check valve package isn't due until Tuesday. I'll either replace the passenger side on Sunday, or wait until after Thanksgiving and take the long weekend to work on it. Shouldn't take too much time from what I've seen and heard, but with this truck, I've learned that there's no harm in being prepared for complications, haha.

 

I'm happy to say that I once again have working 4wd!

​​​​I replaced both hubs following the Ford Tech Makuloco video... That guy has saved me a lot of time and frustration, not to mention money with his videos. Definitely one of the best resources, especially if you're a visual learner like I am.

Not sure what was wrong with the passenger side hub to keep it from locking. I tested it when I pulled it off by compressing it and blocking the vacuum port, and it had no problem popping back out when I took my finger off and released the vacuum. But since I had a brand new part and the original was obviously problematic, I swapped it out. The second I aligned the splines and saw my half shaft turning, I felt good about the decision. I finished bolting it back in place and turned my truck on, and the hub retracted and it spun freely. I engaged 4wd and it locked, and it unlocked smoothly when it went back into 2wd.

I moved over to the driver's side, and I connected a vacuum gauge to the line and tested for vacuum pressure. My gauge showed a solid 15 psi of vacuum pressure, so there was no issue with the vacuum. I proceeded to remove the old IWE and as soon as I took it off, the reason it wouldn't release was apparent. The seal must have failed or something broke inside, because there was something crunchy when I compressed the IWE, and it sounded like there was also grit when it flexed.

I put everything back together and did a final test. Both hubs locked and unlocked when they were supposed to while the truck was up on jack stands, but I still wanted to test the full system. I drove to an empty lot and put it in 4wd and made a couple of tight turns. I was rewarded with the feeling of my truck's front end shimmying as the front axle and hubs were locked and pulling the truck. I disengaged 4wd, and was equally rewarded with the feeling of a normal turn. I drove home and just to be sure, jacked up each side and tested to make sure both sides were staying unlocked when the truck was running, and again, both hubs spun freely as expected. One little issue I noticed, if I disengaged 4wd without my wheels being fully straight, the hubs would not unlock unless I stopped and engaged/disengaged 4wd. Not a huge deal, because it did unlock and lock otherwise, but it did cause me a moment of concern. I also was a little reluctant to test it out on the fly, at least the first time out. I probably will test that out the next time I drive it, since I usually will start in 4wd on an icy area and turn it off once I hit clear pavement. But this was more of a confirmation that the parts were working instead of a full test.

I still don't know what the passenger side IWE's problem was, but I'm glad I ordered both sides. I would like to say 'bring it on' to winter weather... but I'm not that eager to shovel snow just yet. 😜 But when that day finally comes, at least I know I won't be fighting for traction again.

 

Thats a right result. Thanks for sharing your experiences with your IWEs.

I maywell be in a similar position soon.