Auto Hub Problem

[mikeg]

I have an 89 s10 pickup. 4wd 2.8l engine 5 speed manual transmission. the 4wd seems to be temperamental turning on and off while driving. and each time it kicks on or off as i'm driving it sounds/feels like the hub or something is locking (in the front end). when this happens their is a loud knockish sound. Any help with this would be appreciated. I live in wyoming where they don't plow the roads constantly.

[spideyjected]

Check for a vacuum leak, as the hub is operated off of engine vacuum.

[Tink]

I agree, could be a vacuum issue... maybe one of the lines is dry rotted...

For a quick fix, you could feed direct vacuum to the vacuum actuator under the battery tray. When the t-case switch went on my Blazer, I did that... I just put a vacuum T in the line coming from the vacuum ball on the fender and directly fed the vacuum actuator. When I didn't want it in 4wd, I'd stop and disconnect the line going to the actuator and plug the T.

[mikeg]

hm prolly. ive already fixed 2 leaks haha. vacuum ball, you mean that black ball on the drivers side that has one line going to it n no lines coming from it?
anyone know where to get a vacuum diagram?