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Front Axle vacuum diagram/operation

Rogan
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Rogan

Rogan

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Thanks, MM..

The switch itself is very simple and merely swaps vacuum between the red and black lines. All 4 lines go onto the big black connector which will pull off of the vacuum switch. Then you will have just the switch and 4 little ½” tubes where the vacuum lines go. To ensure it is working, take the grey line out and make sure it is getting vacuum (truck must be running). Then pull the red and black lines and the red should have vacuum if it is in 2wd and when you put it in 4wd, the vacuum should switch to the black. You can pull each line out of the 5” or so black hose coming out of the switch so you can feel for vacuum there, just remember where each line went.

Here's a diagram of what I'm looking to try and do, since I already have a couple of vacuum solenoids.

post-10339-138698179367_thumb.jpg

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fire176969

fire176969

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wouldn't that result in a 'vacuum leak'? trouble is, purchasing (2) 3-port solenoids would not justify the savings of just buying a cable :banghead:

Best way to fix them is to permanently lock the axle engaged and eliminate the vacuum system. Those things are nothing but trouble IMHO. Glad mt truck doesn't have it.
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fire176969

fire176969

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That would defeat my purpose then. I'm trying to gain 2wd low, without buying a frigging 200$ bicycle cable actuator. Sent from my rooted EVO's tiny keyboard with my opposable thumbs...

Go to NAPA and get a choke cable kit for a carburetor or a PTO cable. Should be a lot cheaper than $200. If you are looking for another route get an air switch for the power divider lock or suspension dump from a tractor trailer and run the vacuum line to it. Flip one way to send the the vacuum and then switch to release the vacuum. Have to use two switches, one for each line. What would even possibly work better would be a PTO air shift valve that way it locks in whichever position you put it in or even a combination valve like this. http://cgi.ebay.com/ebaymotors/BUYERS-PTO-PUMP-VALVE-K85DF-FEATER-DISENGAGE-RETURN-/250877570047?pt=Other_Vehicle_Parts&hash=item3a6977ebff
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Rogan

Rogan

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MikeR @ TDR

The switch is for the 84-87 Civic EGR and is small and rectangular,about 1x1-1/2in. The body is metal and kinda gold colored with orange plastic nipples.

Really,any vacuum switch will work...just blow through it to make sure its 'open' when there's no power to it. The Honda dealers want about $80 bucks for the switch.

The important thing is the 2 port vacuum switch...you need to get one that is 'open' when it's in the off position so vacuum can flow through normally. I used a Nippondenso EGR vacuum switch for a Honda Civic. They never break!

The rest of the parts list is simple and small:

Rocker switch

5 amp inline fuse holder

1 foot of vacuum hose and enough electrical wire to go from the vacuum switch to the on/off switch.

Tap into the 12V Switched wiring for power and put the inline fuse holder between the power source and on/off switch.

Run a long wire from the on/off switch out to the engine compartment.

Carefully ran this wire along with the factory underdash wire harness and zip-tie it as you go along so it looks clean.

Mount the vacuum switch to the metal bracket above the intake manifold that all the wire harnesses attach to. The vacuum switch has a 'pos' and 'neg' terminal so use a short piece of wire to ground the 'neg' terminal to the same bolt that you use to mount the vacuum switch to the bracket. Now run the 'switched' wire to under the dash,into the engine compartment and connect to the 'pos' terminal in the vacuum switch.

Right above the bracket, you'll see a vacuum tee with two ports...one port is capped and the other is the line that goes down to the transfer case. Disconnect the transfer case line from the tee and plug it to one side

of the vacuum switch and cut a piece of vacuum hose and connect the other side of the vacuum switch to the tee...and you're all done! Simple,eh.

diagram attached...post-10339-138698179878_thumb.jpg

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  • 2 weeks later...
  • 2 weeks later...
Rogan

Rogan

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yeah, you can use a NC solenoid, and it'll be fine, as well, if you cannot find a NO one.

It'll handle the duty cycle 100%, as it's only a relay of sorts. If you cannot find a NO one, you can get an NC one off of any 90s Mitsubishi. They're 99% located on the drivers side firewall. Make sure you clip off the harness pigtail, too..

--- Update to the previous post...

As for NO solenoid, late 80s/very early 90s Honda. Also, check VW EGR solenoids. The NO units are quite common, if you look. :)

I like to take my own piece ov vac. line (about 1' rolled up) in my pocket, pop the vac. lines off the solenoid, and use my piece of vac. hose to test the NO/NC..

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