Join Date: Sep 1999
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Re: 84\' S-10 Blazer 4x4 trouble...
<font face="Comic Sans MS">On a 1984, it'll be a vacuum switch. First check all vacuum lines on engine and leading down under the truck. The switch seems to be on top of the transfer case if I remember correctly. It's been a little while since I've been under one of those, but that's where I'd start. From the vacuum switch thing on the transfer case a hose should go to a vacuum diaphragm assembly somewhere on the passenger side fender or under the battery (varied due to model, etc). That is what activates the front differential. To test whether it engages or not you can try a hand vacuum pump or similar device. Basically if the vacuum lines are ok, then perhaps the device they run to at the transfer case is bad. I'm not sure if it's in the search feature still, but in the past we had some discussion of the system.</font>