HELP! 4X4 disengaging

I have a 1989 S10 Blazer 4X4...just recently noticed that it will not stay in 4 HIGH all the time...it seems to pop out on it's own. I can put it back in to 4 HIGH, but it is very, very easy to push it back into 2wd...it doesn't "lock", and you don't have to use the button on top of the shifter to move it in and out of 4 HIGH. WHat do I do? I need 4X4 where I live, and can't have it popping out on it's own.

Is it the vacuum or the lines or something? IF it is, how do I repair it? Tell me what to look for....PLEASE!

I have a 1989 S10 Blazer 4X4...just recently noticed that it will not stay in 4 HIGH all the time...it seems to pop out on it's own. I can put it back in to 4 HIGH, but it is very, very easy to push it back into 2wd...it doesn't "lock", and you don't have to use the button on top of the shifter to move it in and out of 4 HIGH. WHat do I do? I need 4X4 where I live, and can't have it popping out on it's own.

Is it the vacuum or the lines or something? IF it is, how do I repair it? Tell me what to look for....PLEASE!

Trace all you vacuum lines and look for cracking and bad connections.

I ahd a broken vacum line before though and it wouldn't even go into 4x4. Unless some dirt might have gotten on his line and plugged the hole temporaily.

Where are all the vacuum lines located? I know I read something about under tha battery...