Join Date: Mar 2003
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Re: 97 Blazer Vacuum Problem
I'm not sure I am understanding the problem, Your front axle is trying to engage when the truck is (or should be) in 2wd?
If you look on top of the transfer case above the front output shaft you will see a vacuum switch with three vacuum lines connected. If you are getting vacuum when you shouldn't then this switch is bad or something interal to the tranfer case is broke or out of adjustment.
One of the vacuum lines should be continous vacuum and connects near the brake booster. One is a vent that (on my 2001) is tied to the transmission dipstick tube and releases the vacuum to the actuator when going back to 2wd, and one vacuum line goes to the actuator below the battery tray. There is an indicator pin on the switch so that the vacuum lines can only be inserted fully one way.