Four wheel drive will not engage

Okay, to start vacuum hubs work by first when you put it in four wheel drive the engine vacuum pressures up a canister with vacuum and the vacuum stays sealed in the canister throughout the lines to the hubs, when engaged the vacuum pressure engages the hubs, but if a hose is broken the vacuum leaks out until it has no pressure and hubs unlock, I have an 1998 four wheel drive and I know this by experience. So anyone can call me on it but I found when I got mine that the right tire hub, the vacuum hose to it right where it connects to the tire was cracked and it bleed the vacuum and hubs just disengaged so to start I would remove front tires and look on inside of assembly at vacuum lines for crack or anything then if no problem trace lines to engine looking for any problem if no problem remove vacuum line from engine and see if it is even getting vacuum. Try this and get back to me.

Vacuum reservoir tank and bracket is located either on or beneath the RH front fender splash shield.

See the vacuum diagram below

I have a 1999 Ford Ranger four wheel drive manual. How I found out front wheel drive was not working was the AC would not blow into the cabin at high speed or hard acceleration. I found a broken vacuum line on the right side, so I replaced it and AC works and so does the right tire engage. My left is an issue, The left locking hub is always engaged so I will work on that this coming week. I did find replacement manual hubs at www. Therangerstation. Com (AVM Locking Hub)for $160.00, but I have not tried or bought them yet if I can not get the vacuum ones to work property. While I am on that side I am replacing the 1/2 axle it leaks and has a broken boot.

All these comments are great to read. Educational, would not of known about vacuum, I figure it was all electrical

I can turn the switch on the dash to 4 high or 4 low. I tacts like it kicks in but the front wheels will not pull. I jacked up the rear wheels and tried to drive off in 4 low and 4 high. The back wheels spun but would not pull. I remov ed the electric motor and it is working fine. It has a whining sound in the front end like the 4 wheel is working bu the front wheels will not pull or spin on the rear wheels.

I have the exact same problem on my 1999 Ford Ranger 4x4. I believe the vaccum lines on mine are bad but i haven't got them fixed b/c I did what this page said.
It is really helpfull to have manual hubs and it only taked 10 minutes to add them. I'll probably get the vaccum lines replaced soon so i'll have both manual and shift-on-the-fly! Good luck!

I had to replace the wheel bearings this summer (came with the whole hub assembly). Before I did that, my four wheel drive worked fine. I bought my wheel bearings from Ford, so they should be a perfect fit. Now, with winter snow, I turn the 4x4 on and my front wheels don't move. I've lifted the truck up and engaged four wheel, the front drive shaft and axles spin, but not the wheels. So, I took the wheels off to see what was up. The inner gear/cog of the bearing was spinning.
Now, I am not positive on how the hubs work, but from looking at it (maybe I'm wrong and someone can correct me), but their are two gears in the wheel bearing. The outer one spins with the wheel itself. The inner one is controlled by the axles, driveshaft, and transfer case. The purpose of the hub, is to relay the motion of the inner gear/cog and axle to the outer gear, and turn the wheel.

Now based on my observations, I'm assuming there must be something wrong with my automatic hubs, but they seem fine and my 4x4 worked fine before the new hub assembly was installed. I really don't want to go buy two hubs at $160 a piece or try to find one in a junkyard.

I've read from other sources about o-rings that keep contamination out. If contamination occurs, 4x4 could be lost. But I've also read that the hub Ford used starting 1994 doesn't have this o-ring. I don't know the validity of these sources and I haven't gotten to check the hub for an o-ring either, but it's a thought.

Any suggestions?

The door jam sticker says the truck was build in February 1999. Does that help?

Also, what other types of four wheel drive actuators. Are there? I'm not sure, but I don't think mine has vacuum lines (haven't gotten to look yet because of the crappy weather). And if it isn't vacuum actuated, what do you think the problem could be (besides the hubs because I am pretty sure they are fine)?

I have a 1999 Ford Ranger FX4 4WD and it has just over 96,000 miles. My 4WD doesn't work anymore. At first, it wouldn't work sometimes, i'd have to try a few times. Then it got worse and it would hardly ever engage. Now it won't engage at all. I've only ever used the 4WD for driving in the snow and I do NOT beat on it. The 4WD light comes on in the cab when I flip the switch and nothing happens. The last time I did get it to work, when I turned it off, it had trouble disengaging and made a loud "thud" when I was going down the road.

My terminology may be off. But isn't the hub the outer piece (which on non-auto locking ones is the piece that has knob that needs to be twisted)? (Noted '2' in picture)If so, it wasn't the hubs that were replaced. I replaced the hub assembly (noted as '1' in the picture).

So considering that the 4x4 worked before the hub assemblies were installed - it makes sense that they would be the problem and maybe they are. But, with the truck in the air and the wheel off, spinning the drive shaft spins the inner gear on the hub assembly. Should it? Should is spin the outer gear as well?

I had the exact same problem with my 1999 ranger there two o rings that you need one go just behind the lock out the other seals on the in side of the hub this is what makes your vacum work call ford and tell them you need the o rings for your front hubs if they give you any trouble contact me and I will see if I can find the part number for those orings

The front wheels dont spin at all. I hear the on the fly 4x4 click in, but nothing else happens? Any particular reason for this so a mechanic doesnt rip me off?

Sorry I've been incognito. I've been super busy and haven't even really gotten to look at the truck. Until this week.

So. There is line going into the axle that I assume is a vacuum line. Assuming it worked fine before, there is a problem in the hub - whether mechanical or pressure, I don't know.

PACGDC - you say there are TWO o-rings. I could only locate 1 (before I read your message). Since I didn't know about a second set when I bought the first set, I didn't ask about it. But the Ford Parts person had trouble locating the first - so I am unsure about the second. I am going to drive down there tomorrow and check.
This site directfordparts. Com/ has the Ford parts listed. Maybe you can find the part number there before I go and buy new hubs. The picture I posted above is the best I can do from that website.

Also, in taking the hubs off w/o the special Ford tool, a couple of the little tabs broke off (the hub is held on only by the tabs and then the wheel covers the hub). I know the repair manual and ALLDATA suggest that that could cause the air leak. But it seems improbable to me. Any thoughts?

Just like PACGDC said, there are TWO o-rings. Lovely for Ford to help me out with that. I went in there specifically asking for the o-rings - it took them like 25 minutes to find it.

And it only took about 4 hours to jack one wheel up at a time and replace them - I hate those snap rings they have on there. Those are a pain to get off!

Thanks all! (I love 4x4 in New England)