Intermittent 4x4 '89 S10 Blazer

The 4x4 on my '89 S10 Blazer comes and goes. I just put a new vacuum switch on the transfers case, but the 4x4 still comes and goes. Any reliable suggestions for a fix???

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Don't own a mini-truck?
-The Lonely Grease Monkey 1985' K5 305CUI TH700R4 NP208 KJ's successor
"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson
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Lonely G-Monkey wrote:

Now that was real useful information. No wonder you're lonely. :-)
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Are you just going by the 4WD shift indicator light? If you haven't done so already, throw a few jack stands under it and lookie see the 4WD operation Try checking the switch on the front diffy (by shorting out the the 2 leads the light should come on), check the actuating vacuum hose and how the diaphragm unit's working (located under the battery plate) by using a mighty vac on it.
Just had a similar problem but a new vac switch fixed it
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Check all the vacuum lines and parts associated with the 4x4 system. I had a similar problem on my old truck, replaced a few vacuum lines and the 4x4 worked perfectly. Also check under the battery tray, there's a vacuum soleniod like used for the cruise control that's used for actually pulling the cable to engage the front axle, this may be the problem also.
I've done SOME work on this system, so I might be able to help, but I no longer have the truck to reference, I have a newer one that MAY be different, it's also a little cold to go out and look, -1 out there right now, and dropping...

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