4x4 not engaging

[ISX]

The kit came with the new plastic ears when I put the new actuator on. I have vacuum at the CAD and it SHOULD mean the actuator is sliding when I move the shifter because the 4x4 light comes on, right?

Right, the 4x4 light is switched by the actuator physically hitting the actual switch, so its bulletproof. But its kinda reverse that because it is normally closed (switch is on), meaning when the actuator hits it, it opens the circuit and the light goes out. You might try jacking the passenger side front tire up and it shouldn't spin if you are in 4wd, then go take it out and it should spin. The passenger side axle is cut where the CAD thing is and it has splines on each side of the "cut" and the CAD thing just slips a collar over the splines, interlocking them. It does this so the driver side wheel will just spin the passenger axle instead of the driveshaft when in 2wd, saving u-joints, etc.. I'm just throwing all this out there so you can picture the operation so you can see why jacking up the passenger front tire is the easiest diagnostic method.