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Discussion Starter #1
Ok, so just regreased auto hub w/ new oil and I'm still having the same problem. Whenever i switch to 4x4 with the switch, my a/c blows thru the defrost. When i check the vacuum after the solenoid there is low vacuum going to the hubs and the red line has more vacuum. Anyone know what's going on?
 

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TONS of threads on this.
It's vacuum controlled obviously, the front hubs. You have a vacuum leak. Defrost means there is no vacuum on the blend door actuator and it is reverting to default.
 

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Go to the vacuum pump and trace all the lines. Some go inside the cab, some go to the wheels.
 

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Discussion Starter #4
from the pump there is only a red line, it's tee into the 4x4 solenoid and somewhere into the dash. My vent works fine when I'm not using 4x4. Also is it normal for the vent to blow thru the defrost when i first start up my engine. It only blow threw the defrost for a second or 2 during when i first start up.
 

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from the pump there is only a red line, it's tee into the 4x4 solenoid and somewhere into the dash. My vent works fine when I'm not using 4x4. Also is it normal for the vent to blow thru the defrost when i first start up my engine. It only blow threw the defrost for a second or 2 during when i first start up.
Since your vent setting works fine in 2wd then your vacuum leak is somewhere after the 4x4 solenoid.
It could be one of the hoses going down to the front hubs, or it could be a bad hub seal. Either one of these will cause the issues that you are having.

:)
 

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Discussion Starter #6
how would i know if the hub is leaking, i can disconnect from the hub and blow after the solenoid. But when it's connected i cant seem to blow thru it.
 

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from the pump there is only a red line, it's tee into the 4x4 solenoid and somewhere into the dash. My vent works fine when I'm not using 4x4. Also is it normal for the vent to blow thru the defrost when i first start up my engine. It only blow threw the defrost for a second or 2 during when i first start up.
Did it leak before you pulled the hub?
 

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I am also having this issue. Any idea what size vacuum hose goes to the hubs? I am getting ready to do front ball joints so mine as well tackle this issue to. I am also looking for a vacuum hose diagram if there is such an animal.

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they are such a simple system you wont really need a diagram
you can follow the lines from the hubs up and from the ESOF valve on the pass fender down
 
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