I have went through countless threads with no avail. The 4x4 in my 99' doesn't work. The transfer case does engage (can feel the gearing for 4lo). I have checked the vacuum at the actuator when I press 4hi/4lo and it switches and pulls the cable. The diaphragm looks great, no tears etc.

Plan on crawling under it tomorrow and following the cable back to the axle. The thing I don't know exactly is how to test the cable to see if it is pulling far enough. I've seen some exploded diagrams of the inside of the axle but that didn't help me much.

Curious if I would be able to pull the cable a little more than the actuator does and see if that causes it to engage. Just trying to get a little more input, issue specific while I browse the internet more.

Thanks guys

**EDIT**

Took this from a FAQ's page and other than the rubber diaphragm being broken it sums up my issue. Sometimes the indicator lights switch right away but other times they take quite awhile to switch.

Vacuum actuator failure: Rubber diaphragm breaks. The transfer case changes position, but the front axle never engages. Takes an extended time for the indicator lights to come on.

 

its possible. i had a old 83 s10 where it was similar, everything worked it just didnt pull the cable hard enough. maybe because it was so old, but back on the old trucks they put the diaphrams on the wheel well under the hood so it was really easy to get at i would just pull it manually then put a pair of vise grips on it. so you probably can jack the front tires up pull the cable and see if it engaes

 

After redoing the system on our '96 one of the things I found out is that it doesn't take much of a drop from manifold vacuum or a cable that doesn't move freely enough to not get engagment of the axle. First make sure you've got GOOD vacuum to the actuator via good hoses. Then with the vehicle running you can try pushing in on the actuator or disconnect the cable at the actuator and try pulling on it. I ended up having to replace the hoses and the cable. Working like a champ now.