Intermittent 4x4 '89 S10 Blazer

Don't own a mini-truck?

-The Lonely Grease Monkey

"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

Now that was real useful information. No wonder you're lonely. :-)

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 d>The 4x4 on my '89 S10 Blazer comes and goes. I just put a new vacuum

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