I have a 1990 s-10 blazer 4x4 with a 4.3. I am trying to figure out why my front dif is not locking in. I found that one of my vaccum lines was corroded and so as i'm replacing it, i find tranny fluid in it. It is the line that runs from the actuator to the tc. How come??? Anyone got any explanation for this???

 

Been discussed many times before.

You have two problems that are combining to allow fluid into the vacuum system. The front seal on the transfer case is leaking allowing the transfer case to become over full and the vacuum switch on the transfer case which activates the front axle has failed and is allowing the fluid which is over full in the t-case to bleed into the vacuum system.

I hope, for your sanity, that it has not gotten into the HVAC system yet.

 

How hard is that seal to replace do you know? And also, how would i know if fluid has gotten into my hvac system? I've read about that vaccum switch before. Is that the switch that the vaccum lines run into on top of the tc??? I really appreciate your help.

 

The difficult part of replacing the seal is removing the transfer case. Well, I guess I should say it is more awkward than difficult. There really is no good way to support the t-case with a jack unless you make up something special.

Yes, the vacuum switch for the 4wd is located on the t-case. While you have the t-case down, replace the switch.

If you remove the HVAC control head and there is fluid in the lines there, then...

 

ok, i'll get to that seal a.s.a.p. just to pick your brain again, which i'm sure you get this a lot, you seem like you know a lot, which lines should have vaccum and which one should not? i'm assuming that the line that goes towards the throttle body should always have vaccum and when the vaccum switch is opened there should be vaccum to the actuator. is this correct?

 

There are three lines. One from the engine to the vacuum switch, one from the switch to the front axle, and then one that is just a vent line and should run up to somewhere on the firewall.

So yes, one should always have vacuum whenever the engine is running. The one to the actuator will have vacuum when the transfer case is in 4HI or 4LO.

 

Awesome! Check out the pics i posted of the blazer! I love her! =)

 

Looks to be in pretty good shape!