I have a Mazda B4000 and, with a recent snow storm, wanted to use 4WD the past few days. I notice it switches in 4WD well and works fine for about a minute or two, then disengages on its own back into 2WD. The dash still lights up and displays me being in 4WD, though I am certain it is not. I have to switch back into 2WD, then back into 4WD to get it working again. Repeat. And repeat.

Any idea what the problem is? It switches fine, but disengages on its own quickly...would that been the vacuum? Transfer case? Dirty hub?

Any help would be greatly appreciated!

 

Your '99 B4000 has the "Pulse Vacuum Hublock" 4WD engagement system, which means that the hubs are engaged/disengaged by virtue of vacuum. It is the vacuum part of the PVH system that usually fails in some manner, leading to no/intermittent 4WD.

I recommend you do a search of this forum using the terms "Pulse Vacuum Hublock" which will get you back a multitude of prior threads on the subject. Read through the threads and then post back with any questions.

 

Thanks!

I found an option to permanently lock the hubs via this guide.

My question: is driving in 2WD with locked hubs advisable? I know it's not ideal or recommended, but is there a good chance I will cause additional problems by driving around with the hubs locked? This truck is more or less just a backup vehicle for me to haul stuff around in so I'm not putting more than a couple hundred miles on it per month. Thoughts?

 

Permanently locking the hubs like that essentially makes it a "constant engagement" 4WD system, which is what the 2000-2011 Rangers are.

There are many thousands of Rangers being driven around today with the front driveline spinning along with the wheels (which is what happens by permanently locking the hubs). So I wouldn't sweat it.

 

Explorers went to that setup in 1998. As long as you're not in 4WD on dry pavement, it's OK.

 

I am still confused about having the front hubs permanently locked-in. If my switch is in 2WD, does that mean that the driveshaft from the transfer case to the front is NOT turning? If the hubs are locked-in, then the front axles are turning for sure, so the front differential has to be operating, which will effect gas mileage if nothing else, right? So, is it true that the vehicle is not in 4WD even if the hubs are locked-in unless the switch is in the 4WD position? Any comments that clear this up for me will be appreciated.

 

A further question. When I select 4WD Low, what is supposed to happen? I do hear a cluck in the transfer case, and the vehicle does go into a low drive gear. So that is one thing that happens. Is a second thing that is supposed to happen is that the driveshaft from the transfer case to the front starts turning, or is that always turning. And finally, I know that the PVH units are supposed to lock-in the front hubs. My main confusion is concerning the driveshaft going to the front -- is it always turning, or not?

 

If the front hubs are locked in, then the front driveshaft and axles are spinning when the front wheels are spinning, even when 2WD is selected. This is because the spinning wheels are spinning the axles, which in turn are spinning the front driveshaft and diff. Yes this could slightly affect gas mileage.

When the front hubs are locked in and 4WD is selected, the transfer case engages ("connects") the front driveline to the powertrain. This is when actual 4WD occurs.

If the transfer case is engaged, the front driveshaft and axles will also spin, even when the front hubs are not locked in, because now it's the powertrain spinning them.

4WD LOW is achieved by virtue of the transfer case, as well.

 

Hello Rockledge. Excellent post, thanks for that. I think I finally understand how that 4WD system works. I want to convert my PVH hub-locks to "manual hub-locks. This post explains how to do it:

Adding Manual Control to your 1998-2000 Ford Ranger Pulse Vacuum Hubs - Ford Trucks

Unfortunately, the pictures from this post do not display on my computer. But, from my limited knowledge of the PVH hub-locks, I think I can just drill through the vent screen at the center of the cap and use a blunt object to engage and disengage the PVH hub-locks manually Do you agree?

Incidentally, I see that you have a '98 Ranger like my '99, and you also have a '94 SHO. I still have my '95 SHO that I bought new in 1995.

 

Here's another look: How to convert the PVH hubs to manual hubs.

I'm not sure whether or not you can actually "switch" the PVH hubs manually...I think I recall someone who posted about doing it a while back but I don't recall if it was effective (or reliable) over the long run. My suggestion is that you invest in a set of http://www.ebay.com/itm/1998-2000-Ranger-01-08-Mazda-B3000-B4000-Manual-Locking-Hubs-15001-70-/201079423675?fits=Make%3AFord%7CModel%3ARanger which are designed for that purpose.

You must have paid a pretty penny for your new SHO back in '95. Hope it's treating you well.

 

Dear Rockledge. I was able to contact the person who posted the excellent explanation on how to "convert" PVH to "manual". He sent me a file with pictures that shows how to do it. I can forward that file to anyone via attachment to email. Just email your request to me at fred.furrer@hotmail.com and I will send it to you. I plan to do that conversion on my hublocks today.

BTW, my 1995 SHO cost me around $24K at the end of the model year. I am not driving it now, but I still have it. Want it?

 

Let us know how it works out.

Thanks for the offer, but I don't even have the time (or money) for my '94 right now.

 

Hi Rockledge. I was busy today so I didn't get a chance to complete the PVH to "manual" conversion. However, I did take one hub-lock on my truck apart. I found that it is extremely simple and easy to do. All you have to do is rotate the outer cap (leaving the hub-lock on the hub) of the OE PVH hub-lock a few degrees counter-clockwise (using a needle-nose pliers opened wide to engage the outer flutes), and the cap will come off. Then, the rubber diaphragm, which is actually the "piston" of the vacuum cylinder, comes out. And then the "ball point clicker system" comes out, which consists of an outer plastic cylinder and an inner plastic cylinder with a spring in the center. It is incredibly simple. I am sure this has been well known for years, but since I just bought my 1999 Ranger, it is all new to me. When you look inside the hub-lock, you see the "spline ring" that engages and disengages 4WD. You should have the wheel off the ground to continue. You can easily engage and disengage 4WD by pushing the "spline ring" in with your fingers, and it will eject out due to a spring force from within. If the "spline ring" does not move easily, just rotate the wheel a little to line things up. What I plan to do tomorrow is make two solid cylinders out of wood that are exactly the right O.D. and length to engage the 4WD. I will put them inside the hub-lock and then re-install the cover. Those wooden cylinders will keep the "spline ring" into the 4WD position. I will give you those exact dimensions (O.D. and length) tomorrow. Fred Furrer (608) 697-1249 Cellular fred.furrer@hotmail.com Thanks for all your help on this.

 

Gentlemen. I think I have an ideal, low cost solution for converting PVH hub-locks to "manual" hub-locks. After taking the cap off of the OE hub-lock, and measuring everything up, I realized that all I have to do is create the very same action inside the PCV hub-lock that the vacuum creates. I went to ACE Hardware and bought a pair of plastic "wall mount door stops" (Ace #5295019, 1-7/8" O.D. door stop) which cost $3.99 for the pair. Then I found a spring that fits perfectly into the pocket of the door stop and provided approximately the same force when installed inside the PVH hub-lock -- replacing the black rubber diaphragm and the 3-piece "clicker assembly" that falls out of the housing when the cap is taken off. The spring is Ace #155, 3/4" O.D., 2-1/8" free length, .063 wire diameter and cost me $1.20/ea. I put the door stop and spring into the PVH housing and re-installed the cap. My hubs are now definitely in locked position. Once you get the OE cap off the first time, it becomes very easy to remove and re-install with your fingers. So, if I want to unlock my hubs, all I have to do is turn the cap slightly CCW (while pushing it in slightly) to remove it, then turn the door stop and spring around, and re-install the cap. I haven't actually tried this last part yet, and there could be problems because the spring will have to rotate on the end of the axle, so it should be well greased. The spring is needed because it keeps the cap in place. An alternative would be to remove the door stop and spring, and just find a plastic plug to seal the end of the plastic OE PVH housing. I am going to try to attach some pictures, if I can. If not, the whole thing is quite simple anyway and I am sure anyone can see how it works. I painted a white stripe on the hub-lock housing and cap to show me when the cap is properly installed.

 

That sounds like a very creative solution, I hope you can report back that it works well out in the field over time. If you can, take some pictures and post them, I'm sure a lot of people would like to see how you did it.