first off, you'll need two of the little 3 way vacuum solenoids I have, or functionally similar ones, then you'll need to label, or at least know which port is which, for the purpose of my explanations, I'll call them A, B, and C ports, with the flow being from A to C when there is no power applied, and from B to C when there is power. You'll need to make some sort of a little bracket to hold them, and I mounted it close to where the stock flex lines from the front axle join the solid line mounted on the frame, theres already a bolt there you can use. The lines are colored red and black, I've forgotten which engages and which disengages, but that's not a big deal.
Next, on top of the transfer case, there's a connector which 4 vacuum lines on it, remove it, and it's a good idea to plug the ports on the transfer case to prevent dirt from getting in. On that connector, there are red, green, black, and grey vacuum lines, plug the black and green ones, and loop the grey to the red... now you should have a source of vacuum up by your vacuum solenoids, and it should be the line that had the red tubing on.. you can always run the engine and check... now you'll need some small vacuum line, and a vacuum T fitting... from the constant vacuum source (the hard line that had the red line), use the T to join to the A port on one solenoid and to the B port on the other, the vacuum lines from the front axle may have to be a little unwrapped, they go to the other A and B ports, while both C ports are left open (I have some little filters that fit nicely on them)...
Now for the wiring.. find a switch and a place to mount it, and a source of power that is on when the ignition is on (just like a fog light switch) and run a wire down to the vacuum solenoids, I went through the shifter boot and over the transmission to the frame, then along the hard vacuum lines. connect it to 1 terminal of both solenoids, the other terminal is ground, the mounting bolt is a good place to ground it to.
Testing... fire the engine up, and creep the vehicle forward a bit, if your 4wd indicator light comes on when your switch is off, reverse the vacuum lines that come from the front axle to the solenoids.
Operation.. always engage the transfer case first, then the front axle, particularly important if you're moving, disengaging doesn't matter that much, but I usually do the trasfer case first as well.
for me, it cost me nothing to do this, I had the solenoids from some wrecked cars, the fog light switch was from broken fog lights, and there's really nothing more to it.. I could have splurged and bought new vacuum tubing and that would have cost a buck. The solenoids I used were from a Mazda Rx7, any year will have them, the 86+ are a little hard to get to though, and they have a little mounting rail I hacked up as well. I did this so that I could leave the front axle engaged when I take the transfer case out of 4wd, and that I can use low range without being in 4wd for things like backing up to a trailer on pavement... Any additional questions, email me at
rx7man@gmail.com, I check that more than my private messages here
Haven't gotten a picture of the solenoids yet, I'm working on it... if you want fancy ones, an auto parts store should be able to get them, the fancy ones are used on aftermarket boost controllers for turbos
Experience... What you get just after you need it
I love my shorthorns
