Pulse Vacuum Hublock Solenoid Retrofit for 06 Axle Swap

[lwillson]

Good Day,

Since putting the 06 axles into my truck, I figured I might as well make the vacuum hublocks work. The harley rims have center caps which cover the manual knob, making it difficult to use the manual locking hubs.

Sooooo, challenge accepted

Since I had a donor truck for everything, I had a 4x4 control module, as well as the dash switch for the ESOF and the transfer case. Now the backwards engineering came. I tried wiring up what I could as listed in the wiring diagrams from the service manual, and...... nothing worked at all. That foiled using the 4x4 control module.

No matter what, I needed to use the Pulse Vacuum Hublock Solenoid (PVH Solenoid). This is a regulating vacuum switch, and it is the ONLY way to easily engage and disengage the hubs.

Here is the wiring diagram for it.


After reading countless websites trying to figure out how the vacuum portion works, I finally found one for a Ranger that made the most sense, and it was a very simple explanation. ( I wish I could remember where I found it now).

Basically, the vacuum hub operates like a ball point pen. Apply vacuum, hub locks, apply vacuum again, hub unlocks. The amount of vacuum is different for lock and unlock, which is why there are two different leads for 4x4 and 4x2 on the PVH solenoid. This is why the PVH solenoid must be used.

From what I tested with the truck on blocks, when you ground the 4x2 circuit, 8in/hg is applied to the hubs. When you ground the 4x4 circuit, nothing happens. To get the 4x4 to engage, you have to ground the 4x2 and the 4x4 circuit. This then applies 25 in/hg to the hubs. The manual states that the 4x4 control module applies vacuum for 45 seconds for 4x4, and only 15 seconds to go back to 4x2. With the truck on blocks, I tested and only needed 15 seconds both ways, which made it easier for wiring up a timing circuit.

There are a few wrinkles to the operation of the hublocks that I had to learn on my own. Since its operation is similar to a ball point pen, you have to either remember what state you were in last. The 4x4 control module I think would keep track, but now it needs to be mentally kept track of. Even if you apply the 4x2 vacuum if the hubs are not locked, the hubs will attempt to lock, and sometimes, they will. Sometimes they dont lock, but since there is a possiblility of them locking, there must be provisions made to make sure that the only time you are attempting to lock or unlock the hubs, you know what state you are currently in.

The other design consideration is that the only indication the 96 gives that you are in 4x4 is the light on the dash. Conversley, the only indication that you have that you are not in 4x4 is that the light is out. There is no status from the transfer case to indicate that you are in 4x2, 4x4, neutral, or 4x4 low. This also does not help the fact that if you are going to use the 4x4 light to lock the hubs, they will unlock when you are going from 4x4 to neutral, then they will relock when going from neutral to 4x4 low.

To avoid having a ton of controls and safeguards and having to design some kind of PLC logic to control hubs, I opted for a manual/automatic control of the PVH solenoid.

This was the simplest version I could come up with


The hubs will not lock or unlock unless the trigger switch is pushed. The transfer case has to be in 4x4 or 4x4 low for the PVH to apply high vacuum.
This also allows me to shift the transfer case into 4x4 low and not lock the hubs, to help in moving trailers around the yard into tight places.

I have tested the circuit with the truck on blocks, and everything works. I still have to install it into the truck and make it pretty and integrate it into the dash.

[351fifty]

That's pretty cool, so you have 2 hi, 4 hi, 2 Lo, and 4 Lo, along with neutral? But auto hubs and manual t case?

[lwillson]

2 lo is actually still turning the front driveshaft and the axles in the front diff, but the hubs are not locked.

Yes, manual transfer case, but manual hubs controlled remotely from inside the truck. Essentially I still have to lock the hubs, but now I dont have to "Get out in the mud and lock the hubs" as the old Chevy ads used to say.

[351fifty]

But esentially you have 2 low or non locked 4, is your rear LSD?

[lwillson]

yeah, rear LSD, but when I am using "2 low" its not like I am rolling in the mud, its just easier for moving stuff around.

[ol_Blue97]

i was gonna get in to this soon for my hubs too..... i will be watching. didnt know that the vacuum swa so intergrated. i thouhgt just on... off.... that was the advantage you had in the parts trucks. did you rob the stuff out of that truck?

[lwillson]

Originally Posted by ol_Blue97

did you rob the stuff out of that truck?

Yes, and no. I robbed the control module and the PVH solenoid, but the solenoid was broken. It must have taken a wack in the rollover.

That added some more fun when trying to figure how it works, when the one component that I needed didnt work.

I picked up some switches at the wrecker today, hope to make it look a little more factory than just a push button on the dash.

[lwillson]

Since we had our decent fall, winter finally came



That meant that it was time to get these hubs working, so I can go play in the snow

I scrapped the timing circuit idea, and went back to the wrecker to browse everything that I could find that I could make into something decent. I ended up with a Door lock switch and a window switch out of a 98 Mercury Mystique. They seem completely different to all the other fords I have worked on. I only needed the switch from the door locks (to get a switch that was labeled U and L), but I needed the harness from the power window switch. It has 2 more leads on it, which is essential to make this work.

I sat and looked at the schematic for a couple of hours (felt like days, because something just didnt seem right. The problem is that for the PVH to unlock, you need to ground the 4x2 wire, but to lock, you need to ground 4x2 and 4x4.



Once I figured out a way to do it with the window switch, it was time to get it into the truck.



Soldered up some wires, cut a hole in the dash, fired up the label maker and I was finally done





It was the only place on the dash that I could find that I had enough room behind for the factory style switch with harness. To operate, just hold the lock or unlock for 15ish seconds, and presto, everything works. I will try it in the snow tomorrow, but I had it on blocks, and it seemed fine.

[351fifty]

If only you could add an led to let you know it is in the locked position, looks great, when I do my swap if my axles have the vacuum hubs like yours I'm def gonna put the button there, looks almost factory too.

[ol_Blue97]

with the vacuum hubs i dnt think there is a way to actually let you know they are locked with out somekind of micro switch inside the hubs???? otherwise it would just tell you vacuume has been sent to the hubs.