On my 1995 Blazer. First off, where is the identification for the transfer case type?

My main issue is that I believe the transfer case and frontend is engaged all the time. I've traced all my vacuum lines and they are all correct per the diagram that has been posted a few times on here.
Nothing is pinched. I am not sure as of hose locations on the transfer case itself, but the little tab was lined up with a small detent in the hose manifold(at least I think so, I was working on the front half of the trans install). I'm going to be checking that tomorrow though.

What I have checked so far:
*Switches are not made unless buttons are pressed.
*I can hear shift motor run when switching between 2hi and 4hi.
*Ohm'd out vacuum switch for proper operation when vacuum is applied to actuator under battery.

This is where I found the problem. What struck me as odd is that I have vacuum all the time. On the diagram it shows as open to atmosphere, which would create a vacuum leak and make the engine run horribly.

Should I always be pulling vacuum to the actuator, or not? I was not able to see if it was moving in either 2hi or 4hi. I can check that as well.

If I have a vacuum leak in the transfer case causing this problem, I suppose I can find an EGR vacuum valve to use so I can switch between 2hi and 4hi.

 

You should not have vacuum all the time. There is a "switch" located on the t-case. It is a vacuum switch that applies the vacuum to the actuator, thus engaging the front end. The switch has 3 vacuum lines that come from it and run up into the engine bay. Generally replacing this fixes the problem that you're describing. The switch is located on the top of the transfer case

The vacuum switch is like a 20 dollar part and looks like this:
http://www.1aauto.com/img/ucart/imag...00004/main.JPG


As for the which type you have. There should be a round metal placard on the back of the case that should have a number on it. For example if you have the NP233/NV233 you will have 3 buttons on the dash (this is the most common transfer case in these). If you have a manual transfer case shifter it is the NP231, and if you have 4 buttons on the dash, you have the NV236 transfer case.


Hope all this helps

 

Shortly after posting I came across a few threads about the vacuum switch. After seeing a picture of it I realized that's the only thing that could be causing the leak. I'll pick one up and see what that does for me.

Wish I would have discovered this while the case was out instead of trying to do it up in the vehicle.

Thank you for the help.

 

If you have the ZR2 model of Blazer, it's actually not a bad change, it is on the regular models that it becomes a pain in the butt

 

Well, it was a bit of work, but after I pulled the crossmember and dropped the tail down it wasn't to bad. Changed the switch, replaced some rotten vacuum line and the 4Low indicator light for $20+change. Took about an hour to do it all.

Thank you for the help. I'll find out if it works in the morning as soon as I get some coolant back in the system.

What sort of a milage difference is it when you drive around in 4wd all the time?

 

When mine went out about a year and a half ago, I was averaging about 12-13mpg in town and only around 14-15 on the highway. That plus the annoying noise that would sometime come from the passenger side front tire, made me realize something was the matter.

After replacing the switch the noise went away and my mileage jumped to around 15 in town and about 18-20 on the highway. On a side not, a full tune up (Plugs, cap, rotor, wires, Air and Fuel Filter) always tends to help your mileage a little bit.

 

All I have left are plugs and fuel filter. I have my compression tester ready as soon as I get up the nerves to attempt removing that plug behind the steering shaft.

Tested 4wd operation and it switches back and forth now.

I was just curious on milage because a friend told me they arn't to bad for vehicles, but do poorly on fuel. I'm wondering if that was the reason behind it.

 

Driving in a straight line in 4WD on pavement isn't really hard on it, but turning on pavement you'll hear it whine and groan. Only time you should use 4WD on pavement is if the roads are icy/snowy and it's unsafe or impossible to drive in 2WD.