4x4 engaging, but not fully engaging?
 

2001 Blazer 2-door

When I push 4-HI, or neutral then 4-LO, both times the lights stays on, the relay in the passenger side kick panel clicks and I can hear/feel something underneath the floor panel engaging/trying to engage which I assume is the transfer case or something. But no front wheel movement, any ideas?

sounds like vacuum troubles...

The cable that engages your front diff is controlled by a vacuum actuator, located under your battery try on the passenger side. Not enough vacuum, and it will not engage fully. Your transfer case and switches could still be working just fine.

Specifically, be sure and inspect the vacuum hoses right behind the ABS controller. Those commonly will deteriorate and cause vacuum leaks which can cause the problem you're having.

Plan on replacing the vacuum lines as Toby stated. If original, they are trash.

You can begin by pulling the battery out, then the battery tray. This expose the actuator; follow the vacuum line all the way...through the T and all. Bet you find one or more sections of rotted hose. Suggest buying enough hose to replace all.

Good luck.

Getting my 4WD working properly
 

Got through last winter with 4WD reluctantly working but with sluggish response and banging coming out. After checking related threads I'm planning to replace the vacuum lines - seems the most likely cause.

Only thing that vacuum lines run is the front axle engagement. That is easy to check. Just jack up your right front wheel and try to turn it, It should turn easily in 2WD but not in 4WD.

What you are hearing is the encoder motor shifting the transfer case. Does it shift normally between 2Hi and 4Hi (no banging and light for selected mode comes on steady after fashing for a bit)? To get into and out of 4LO you need to be moving several miles per hour and coasting with your trans in neutral. It's in the owners manual. Probably still grind a little going into and out of 4LO. Why do you need 4Lo anyway?

Was kinda having same issues...Don't know what I did but now its working as advertised...