Hey guys... 96 blazer and the 4x4 doesnt work. I've been reading a lot of old threads and of course Hanr3's writeup on the 4x4 system.

After testing the front driveshaft in 4hi, my problemhas to besomewhere in the vacuum system. Id love totry tofix this myself if possible butits tough because I dont know what a lot of this stuff looks like. I've searched around old threads and unless I missed something, I couldnt find any good pictures of what I should be looking forwhen searching for my problem.

If anyone has any pics they canpost of what I should be looking for (t-case, vacuum switch, the three hoses on the t-case, etc.) Pictures always helpme out when im doing something new and i'd really like to fix this without having to pay some mechanic.

Thanks

 

ok so im trying to do the vacuum actuator test and i have a couple questions. I used some pliers and the cable move fine without any lubrication needed. I disconnected the hose and Im having someone put it in and out of 4hi and i hear hear the air blowing out as its being put in 4hi. Does this mean my vacuum actuator is the problem?

 

I'm fighting with my '99 as well.

Does your dashboard light come on when its in 4WD??

If it does, then ( If I understand this correctly) the actuator cable is moving enough to trigger the switch that is at the end of the cable right at the Differential.
That's what I am getting and that is why I cannot figure out what is wrong.

If the cable is off the actuator so you can look up in there, and you apply 4WD, can you see the actuator pull in? With all four tires up off the ground...With the cable off the actuator, put the vehicle in 4WD then pull up on the cable, do you get the front wheels to turn??

 

What you could do is go out and buy a vacuum pump gauge. Hook it up to the actuator first and test the vacuum on it to make sure A. there are no leaks and B. that it operates.

If it works then you should hook up your vacuum gauge to the line the actuator is connected to, start the truck and switch on 4x4. You should see a steady volume over 20 psi (?)

If not, then you need to goto the vacuum switch and check the connections and take it out to make sure the ball is not stuck. If that is fine, look at your t-fittings near your brake booster, make sure the vacuum is connected to the ball reservoir, etc to find a leak.

I just went through all of this.

I don't think the that switch tells if the cable is moving or not, at least not in my circumstance. My lights were working fine and my vacuum switch was never connected so the cable never moved but I never got an error.

 

If that's true, then what the heck is that switch that goes into the Diff do for a living??
Definitely getting vacuum to the Vacuum switch on the transfer case.. I didn't have the time to continue down the path to the actuator. On the '99 you have to pull the battery tray out. If it ends up being the actuator, I'm scrapping the whole deal for the Mechanical cable that can be installed in the car. Who needs to lose 4WD do to Vacuum issues when you really need to get out of mud or snow?