Hi F-150 gurus, got another problem with this Ford. 98 F-150, 4.6, 4x4. When I try to engage the 4-wheel drive, the front wheels don't engage. I just changed the electric drive motor down on the transfer case, I can feel it clunk when the switch is turned, so that works.
Does this front axle alway stay engaged? The way the front hubs are designed, it doesn't look like you have a choice of putting a manual locking hub on it. The only thing I see down on the front axle is a vacuum operated diaprahm. How do you go about checking that part?
If I have to end up taking this to the dealer, I would like to have as much info as possible before I go there. Any opinions on what you guys would check next?
Thanks for the help, this is a great site, been very helpful to me so far.

 

I've got almost the same problem with my 99 F-150. Only thing though is I'm not hearing the clunk. I checked to make sure my front drive shaft was moving and it was. Have you had any progress on your problem from other sources?

Green Lantern

 

I stopped at the dealer and asked them what usually goes wrong. Around this time frame, Ford didn't use locking hubs like everybody else, they use a system that locks the axles in the front hub. There is a little vacuum operated diaphram down on the front hub that moves a lever and engages the axles. I guess it sticks after a while. You can try a suction pump on it and see if it moves the lever, if not it needs to be replaced for about $146.00. If it does move then it is the pump up on the fender that creates the suction that is bad.
Always something with these trucks. You fix one thing and in a little while something else breaks on you. I guess it happens to all makes and models.
There is a lot of knowledge and experience on this website. But more remove and replace, go fast, look pretty kind of stuff. Not as much pure technical knowledge as we would like sometimes. But the guys with the real knowlegde probably work at the dealerships and if they give up the goods, they would have less work to do.
Good luck with your deal, please let me know if you find anything out that helps.

 

Other things it could be other than the vacuum motor on the diff is a leak on lock up line fro the solenoid, or a bad solenoid. On the firewall, passenger side at the top, you will see 2 solenoids that put vacuum to the lines to the diff. One is used to lock the front diff, the other is used to unlock. Not sure which is which. The other problem was the vacuum motor itself. Sometimes dirt and mud would get in there and cause it not to work or it was bad.
I had a similar problem on my 98. In my case, it was a bad vacuum line.

 

I have a 97 F150 5.4 4x4. When I bought the truck, the 4x4 didn't work. The front front driveline would turn, but it wasn't engaging into 4x4. My problem was the selenoid that engages it into 4x4, located as said above on the passenger side on the firewall, kind of behind the battery, was the problem. What we did to figure out if it was the actual switch, underneath the truck, behind a dust shield, or one of the selenoids or a line was this:

We switched the vaccum lines running from the disengaging selenoid to the engaging selenoid and it would work the switch underneith the truck. (this is a lot easier with two people, one to watch the switch under the truck, the other to move the 4x4 shifter.) The opposite vacuum hoses would move the switch, just in the wrong direction. Engaging hoses on the disengaging selenoid, so actually it was the direction for the selenoid, wrong direction to engage it. Hope that makes sense? But when switched to the engaging selenoid, it wouldn't move the switch at all using the engaging vacuum lines. We knew the actual switch was good, because it would move. So we were left with two choices, bad hoses or a bad selenoid. Since all of the hoses worked on the one good selenoid (disengaging) we knew it had to be a bad engaging selenoid.

The engaging one on my truck was the left one (looking at the truck from the front end, it would be the passenger side selenoid). Asked Auto Zone about it, they said it's a factory only part. Called the Ford house, ordered one at Auto Zone's price (got a good connection. lol) and cost a grand total of 32 bucks and a some change.

Hope this helps some... If it doesn't exactly make sense, I'll try to go back over it in better detail if needed.

BT

 

I haven't had a lick of time to even begin working on my truck. Been working long days and weekends and I have a 10 month old. So ..... I'm kind of mooching off you guys right now for the expertice. It might not be till next month that I get time to work on it but I will be sure to reply with what I found to be the problem and what I needed to do to fix it. Can't say enough on how much I appreciate xexman44 for posting the question and the dealers info. And to the other guys too.

Green Lantern.

 

Check the vacuum line from the vacuum canister to the diff. They sometimes get leaks in them so they don't hold vacuum.

 

I checked everything like all of you guys mentioned. I unhooked the lever off from the vacuum diaphram and found out it worked ok. I did check all the upper solenoids like the other guys mentioned. Everything up above seemed to work fine, luckily.
I ended up draining the oil from the front differential. It looked like it had water in it, all smokey looking. I drove the truck around for awhile and kept trying to engage the front wheels. After a while it started working. So now it works fine. And I didn't have to take it to the evil empire to get it fixed. Lucky for me. I hope this helps somebody if they run into the same problem.
What goes out next so I can start learning about it?

 

I've had a similiar problem to this and it sometimes locks in just fine and other times it takes a mile or so to lock in. Seems that if I get it locked in once, it will lock in right away when I need it again in a short time frame. If I go a month or more without evern locking it in (working too damn much) it seems that it won't lock in for quite a while again. I've learned to lock it in more often to avoid the nasty problem of not locking when I need it most, but there's got to be a better solution.

Since it works most of the time, should I assume the lines and solenoid are working? Is it possible the switch or solenoid might fail on occasion but work others? My guess is the switch underneath is getting stuck. Any advise on how to "un-stick" it. I'm a novice mechanic at best, but I'll take a wrench to it if I think I know where I'm going. Any advise on replacing the switch?

Thanks everyone for your great support of this site.

 

Hey guys!

Would like to thank you all for info on this subject as I too had 4x4 problems in my 97 4.2L.

After taking it in to my local and TRUSTED mechanic for a diagnosis, they said it was either the electric motor on t-case or the shift fork in diff. which they could fix for about $150.00 in parts and probably $200.00 in labour (for you Canadians out there).

I said BS and came right here. This post specifically helped me tons and saved me some loot. After looking at the front diff vacuum diaphram, I followed the vacuum lines up to the solenoids and right by the battery in the blue hose (engaging vacuum, I think) there was a huge hole in the sunogun!

I just taped 'er up just to see if that would work and voila! 4x4 kicked in....no noises or anything! The "mechanic" should have easily spotted the hole, it was that big....you could hear and feel the vacuum....I'm NEVER taking the truck back there again...after 3 plus years AND they work on my parents and brother's vehicles. A real disappointment.

Now that I know it is the vacuum lines, I'm gonna replace 'em both as they both seemed brittle.

So thanks to you guys who pointed me in the right direction, F150OL certified is better than ASE certified.

beowulf

 

Just goes to show you that not all mechanics truly know what they're doing. You would've paid them to change the actuator on the front axle, and it STILL wouldn't have worked.

As was already mentioned, the most common culprit for this is the vacuum solenoids on the passenger side firewall. They tend to stick from lack of use. When you flip the switch, the engage solenoid sticks in the off position, or the disengage solenoid sticks on the on position. They should BOTH change state when you engage and disengage 4wd. If one of them sticks in either position, you end up with either vacuum or NO vacuum on BOTH sides of the diaphragm in the actuator and, therefore, nothing moves. The quick and dirty trail fix for this is to swap and/or disconnect the vacuum lines as necessary to get it to engage or disengage.

Why Ford didn't use a single double-acting solenoid is beyond me?!!?

For those that prefer it, there are two options to eliminate every possibility of that problem: The first involves swapping out the drive axle from an Expedition which doesn't use the Center Axle Disconnect in favor of a live front axle, or pick up the manual linkage from 4x4posilock and install that.

For me (for now) I know how to band-aid the system should it ever try to leave me stranded. Should I ever decide to start doing some hard-core wheelin', I'll think about going to the posi-lock unit.

-Joe

 

Finally got around to working on my truck this week. It was indeed the selenoid, the one closest to the passenger side, that controlled the truck going into 4WD. First we got out a volt meter and tested to make sure we had current going to the selenoids. You want to check before and after switching because the amount of voltage is different per selenoid and it will alternate switches once you throw the 4WD lever.

Next, as it was described above, I traced the vacuum lines down to the transfer case. Unhooked those and the the red one had suction. Threw the lever into 4WD .... nothing. No suction on either line.

Went back up and switched the lines at the selenoids, and instantly we had suction now on the blue line. At that point we could rule out a bad line. Called Ford and for $31.30 I had the new selenoid the next day. Put it in and it works fine. Can't say how much I appreciate all the info from this thread, it saved me a fair amount of money!! L8R.

 

Actually, the reason for the different readings is because the GEM switches the GROUND for the solenoid. The thing to look for is whether or not you have 12V on the appropriate wire at all times, and continuity to ground at the appropriate time.

Glad you got it fixed though...

-Joe

 

I had the same problem with my 97. Some times the 4 wheel drive would not work and finally gave out all together. I found that the vaccum motor was engaging, but the axles were not locking together. After removing the front axle out of the truck I found the the vaccum motor operates a fork which moves a connecting ring gear to lock both axles together. The fork had plastic slippers on it which slipped over the outside of the gear. These slippers were broken, which in turn would, most of the time, not push the gear ahead enough to lock the axles together. When I went to Ford to get replacement slippers, I found that I had to buy the whole fork/ring gear assembly which was about $240. After my anger subsided I noticed that the new ring gear in the kit was different from the original one the truck. The old one was tapered on the face of the gear while the new one was flat. I'm thinking that Ford change the style of the gear to prevent slipping on the axle shafts which was why they made me buy the whole kit. After replacement the 4 wheel was working great. I hope this helps. Good luck. Tony NY

 

I also have an 8.8 ifs front axle that doesn't lock rendering 4x4 inop. Anyone with any pic's of the ring/shoe assembly that locks it together ? I would like to have the shoes made out of steel instead of plastic and would like to see some pic's before I pull the truck apart. Does this sound possible ? Anyone ?