94 s10 blazer differential problem

I need some help troubleshooting my 94 blazer's 4wd. I have tested everything all the way to the differential. I have the push button and when I push 4 hi the transfer case shifts and the front drive shaft is
engaged. I get vacuum through the switch on the transfer case to the actuator under the battery and the cable appears to move. I get some noise from the differential when all 4 tires are off the ground but they fronts never lock in. What is supposed to happen in that differential that is not working and what do I do next to get it working. I have tested the actuator by turning the 4 hi on and it sucks the bladder in I then pulled the vacuum line off and put my finger over it this help so the bladder has to be good. I don't know how to test if the cable is good.
any help is greatly appreciated
kevin
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According to my Haynes manual (looking at the blow-up diagram of the front diff), the cable attaches to a shift fork in the front diff, which slides a gear towards the driver's side of the diff. The gear slides into a sleeve of sorts, with teeth to mate with the gear. This engages the front axle. Not sure HOW exactly that happens, just explaining what the diagram shows. I have a 94 Jimmy, so my book would cover your truck as well. Beyond that, I can't help ya, mine has worked VERY well this year, even handling some freezing rain that brought out the chains for the salt/sand trucks.
On 17 Dec 2003 05:27:20 -0800, snipped-for-privacy@hotmail.com (Kevin) wrote:

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