Wires

[old school truck dude]

These are the 2 connectors on my front axle of my 90 GMC ext cab IFS. Which one do I use to hook a switch to in order to lock in the front axle?

[xjs3667]

the 4 plug one....

[old school truck dude]

the 4 plug one....

Theres 3 wires that go to it, one hole in that plug has no pin

[ToughBowtieTruck]

Trace your wires. You want the two wires that go to the can that's mounted on the axle itself. It sits in front, along the axle tube. It's just a gas-operated plunger, electricity is used to heat the gas, expand it, and move the fork in the front axle to lock the front diff.

I have used simple toggle switches (ones with a LED on the end so I know it's on) and mounted them on the shifter rod to enable me to have both 2 wheel low range and as a cheap fix to messed up harnesses.

The other wiring is for the 4x4 light. The light won't come on until the front diff is engaged.

[old school truck dude]

 

[BIG DOG]

have you pulled it out and made sure it works    battery charger it comes out a little and goes back in as soon as you take the power off   ..dont matter which side  /  also your t case has a check valve  its a plug in one on the top also  .

   you could just  ground the acuator  to the frame  2 ft of wire   . then run your hot wire  from battery to switch down to the acuator. 

[xjs3667]

also the gas operated ones are prone to being a pos and and never working...... you can easily switch it over, to an electric acctuator switch .... just buy one for the 95+ trucks, it screws into the same hole and you will have to buy an new wire harness from dealer that converts it over.... If I remember right it was around $40  or you could always make your own, if you have a diagram, but it was nice when I converted mine, there is no waiting for the gas to heat up for it to lock in and in winter time it might never lock in..... not good in a plow truck.... switch to the electric actuator and it locks up instantly when you put it in 4 low, and you could even throw a toggle on it to lock it in 4 highh if you wanted to

[old school truck dude]

Cab is 2wd, its on a 4wd frame. Gotta just hook up a switch cuz theres no existing wiring for any of that stuff.