Help!! 4WD

I've got a 95 Blazer with auto & 4wd. Found out in recent snowstorm that front wheels are not locking up; Transfer case does its job...both drive
shafts are rotating, but front wheels are free-wheeling. Any suggestions for do-it-yourselfer as to possible fix or further inquiry?
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I may be completely wrong, but I thought that all Chevrolets after '89 or so engaged the front drive axles in the differential via a vacuum actuator in the S10s or a motorized actuator in the full size trucks. The drive shafts will always rotate with this setup. I think your problem may be in the actuator, but one of the readers (Who owns a full-size) on here can tell you for sure or not though.
-John '89 S10 Blazer 4.3L; 207K

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This is an S-10 Blazer. I do not have a factory shop manual, and you may be right about the front drive shaft...I guessed it was engaged when the transfer case electric motor made its "shift", say to 2H. Can someone point me to this vacuum actuator or someplace in its system where it can be tested/checked?

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Ist step....did the 4WD indicator light on the floor shift assembly light up? my guess...probably not.
2st.....underneath the battery plate is a vacuum actuated diaphragm which engages the front differential.. That may not be getting vacuum thru a lever operated vacuum switch on the transfer case... Had mine go out a few months ago....aftermarket cost about 30 bucks
but also the diaphragm might be ripped or a vacuum hose split or worked it's way off the source
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Under/around/behind your battery (or the OEM battery locator) if I am not mistaken.... If not there, I think it may be on the axle. /never worked on one before....
~KJ~

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The vacumm switch is on the transfer case ( top passenger side) and the diaphram is on the fenderwell behind your battery. Check for vacum at the diephram with your shifter in 4 wheel drive. If no vaccum then check the switch ( three lines) for vacumm and trace out the lines for leaks. If no leaks and there is vacum at the switch but not at diaphram then switch is bad. If vacum at diaphram but no hubs locking up then diaphram has a hole in it. In the previous post he said he could get them for 30 bucks, call him and have him get you two cuz where i live they are 87 dollars. Hope this helps you out.

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