Looking for a little help with 4WD. Transfer case switches, front hubs do not engauge. Driveshaft engages.
Checked vacuum actuator. It's kinda sticky, but appears to hold vacuum. It may be working.

Started the car and put a vacuum gauge on the hose to the actuator. Hit the 4wd button. Lights indicate truck is in 4wd. Still no vacuum at hose. I'm guessing a bad leak or a bad switch.

I looked for the switch, but cant seem to find the dam thing to save my sole. One post said passenger side, the other said driver side. A little more help please if you can? Vehicle is a '98 blazer. Also, can someone please tell me where the vacuum source is? I couldnt find that either, and if its a leak, I'll need that too. I am guessing the vacuum vent is the hose taped to my tranny dip stick?

One more thing: Looking at the hoses heading towards the transfer case. There appear to be two that are attched with a "y" peice of tubing that goes to the case. No idea what that is either. Posts on here say there should be three going to the case?

Thanks in advance,

 

https://blazerforum.com/m_52228/tm.htm

Start here, and ask if you still have questions.
Vacuum switch is on the drivers side of the t-case, next to the front driveshaft, three vacuum hoses go into it. The hoses ...... read the thread and I cover the hoses pretty well. Post up if you still have questions.

 

Actually Hanr3, I started with your message. Thank you very much for that post. If it wasn't for you, I may have given up. The service manual seems to have missed providing the excellent information you did.

My questions still stand from my previous message if you can answer:

When in 4wd, should the actuator have vacuum? I'm guessing yes, confirming that I have either a vacuum problem or a switch problem.
Using your photo's, I was able to locate the switch with some effort. It was much harder to see then I anticipated, hence my questions. I'm am skeptical about actually getting a wrench in there.

Do you know where the vacuum source is? I believe I have located the vent, but am having difficulty finding the source. If it is indeed on a Tee by the distributor, I will look much harder to find it. I was requesting confirmation hopefully from a source who knows.

Since I have found the switch, no need to respond about the tee I mentioned, its inconsequential.

 

I have replaced the switch on the transfer case.
I now have vacuum at the actuator under the battery.
The vacuum actuator appears to be working well/properly.

4wd still does not engage. Broken cable? Front Differential? Any ideas?

 

The two hoses with the "y" are the vent lines for the t-case. That hose should end by the distributor and has a foam thingy on the end of it, should be attached to the firewall.

Vacuum comes from the backside of the intake manifold. Look for the vacuum line on the passengers side, it provides vacuum to the t-case and HVAC system.

If your getting vacuum to the device under the battery tray and that vacuum modulator is holding vacuum they your cable could be sticking or its broken in the t-case. I haven't lloked at how the newer vacuum actuators are conneccted to the cable, however you should be able to diaconnect it and pull on the cable with a pair of pliers. May have to rock the truck back and forth some to get it to engage. If that works, verify the vacuum accutaor is in fact working. Also verify you dont have a vacuum leak in the hoses to the vacuum switch on the t-casase and from the vacuum switch to the vacuum actuator. Put your vacuum tester on the battery end and see how long it holds pressure. Should be pretty much forever, or until you push the button to go back into 2hi.

 

Thank you sir. I do not believe there is a vacuum leak, but I will double check. The actuator really yanks on the cable hard. The cable does move both by hand, and under vacuum. I can see it pull in hard when the 4x4 button is pushed. Prior to changing the switch, nothing was happening, so the vacuum switch at the t-case was certainly bad. The actuator works much better then I expected from fiddling with it. I will investigate the cable more thoroughly, but it sure feels like it is working. It moves about 1/8-1/4", and then you feel a click, as if a switch was being engaged, and it pulls about 1/2" to 3/4" of an inch total. Unfortunately, the 4wd still does not seem to work at the front wheels. I will check the cable at the transfer case next.