I noticed what looked like ATF fluid on the hoses, the fluid was pinkish. What is this check valve for? I see a hose that is not the correct size btw that goes to the back of throttle body area and then to this valve and several hoses coming off it in all different directions. I do remember seeing some type of liquid in there when I first got this Blazer.

I found this diagram.

 

The transfer case input shaft seal is leaking, (transfer case must be removed to replace the seal). The O rings in the vacuum switch on the transfer case are also leaking, (switch must be replaced). When the fluid level in the transfer case rises above the vacuum switch, the leaky O rings allow manifold vacuum to suck transmission fluid into the vacuum lines. All of the HVAC vacuum lines, actuators, and control switch in the dash, the vacuum reservoir in the driver fender, and the 4WD vacuum actuator under the battery, and the vacuum line for it, must be thoroughly cleaned or replaced as necessary.

If you remove the transfer case fill plug, (upper plug on the rear of the transfer case) fluid will pour out, indicating it is over full and confirming the above. Not a fun job

 

Is replacing the shaft a pain to do or is it easier just to buy a used or new transfer case?

I just replaced the switch several months ago, think it went bad on me?

 

And do you think this is why I couldn't get the truck out of 4 wheel drive?

 

The input shaft seal is not difficult to replace, but, the transfer case must be removed, which is time consuming. Fluid in the lines will cause problems with the HVAC air distribution and with engaging/disengaging 4WD. If the fluid is not completely removed during the cleaning process, you will have problems. Keep in mind that transmission fluid deteriorates rubber quite rapidly. Any rubber components such as lines, diaphragms, etc, that it comes in contact with will be compromised.

 

I replaced the vacuum switch several months ago, will I need to replace it again? We are going to try and fix this next week so I need to know if I need to buy a new one again. I don't remember an o-ring this switch unless you are talking about something else. I replaced the switch that has the 3 vacuum lines and ball bearing on opposite side.

Or are you talking about this?

http://www.partsgeek.com/gbproducts/...FQcOaQodtYUA2A

 

And how do I replace the vacuum reservoir inside the fender? Do we need to remove the fender?

 

On the diagram, where do lines A and B go to? I need to know what size vacuum hose to get and how long.

Do I need to also replace the 3 way valve that sits by the fender?

What else am I missing the needs to be replaced or cleaned?

 

The 3 button, 2 speed selectable, (NV233) transfer case uses this style of vacuum switch mounted on the transfer case:



It has O rings inside, (not visible). If the O rings are leaking, (which they apparently are) it will need to be replaced.



The 4 button, 2 speed AUTO, (NV236) transfer case uses this style of vacuum switch mounted on the firewall:

 

This just crossed my mind....

So I noticed that the transmission fluid level is always where its supposed to be. But the transfer case, if left unchecked will be almost empty. There are no leaks in sight by the transmission or transfer case.

So if the input shaft seal is bad, how does the fluid level in the transmission stay the same but the transfer case almost empty? From my understanding if the seal is bad, the fluid from the transmission leaks into the transfer case which fills up to the actuator and then vacuum is pulling the fluid thru the vacuum line, is that correct or am I backwards?

Is it possible to manually over fill a transfer case?

Where is the fluid going too when it leaves the transfer case if the above what I mentioned is correct, If I'm wrong on what I said then I know where it's going, I think.? I'm just trying to think of everything before we dive into this and repair items that don't need to be repaired.