Well I am from vermont and as we all know in vermont 4x4 is a nessary in vt especially in snow I noticed after my blazer is warm and i go to push into 4x4 in neutral or in drive etc like i always have my blazer will not always go into 4x4 or even 4x4 low i have to switch it a few times before it will finally go into 4 wheel or sometimes after i put it into 4 high and go to drive forward i hear a low clunking sound than than it works, all gear fluid are up to date brand new front hub assemblys cv shafts are fine, I did do some reseach online and was seen somthing about the 4x4 module on the kick panel on the passenger side, I was hoping to get some sort of input from someone who may know or have experienced this issue, and i also noticed tonight when i was in 4x4 wheels straight my 4 wheel drive clunked for no reason like it kicked out of 4x4 and back into 4x4, I am really thinking somthing to do with the module just havent pulled it yet to verify ...

 

It could be a vacuum leak to the actuator that engages 4x4. Remove your battery and then the battery tray. Underneath it you will find a diaphragm an some hoses. I would start there first. You need to fix this problem before it really damages something.

 

Check all the hoses and search on here for tons of threads regarding the same condition.

 

if your front driveshaft is locked in then its a issue with the front axle. had a 97 come into work the other day, the transfercase didnt engage, so i started with the simple stuff, pulled off the connector at the encoder motor and checked the module by the passenger floor board and all seemed ok, put them back together and the transfer case started engaging. dont know what i did but i fixed it.

now the front axle didnt work, ended up the vacuum actuator under the battery that pulls the front axle into lock mode was broken, with a big rip in it, replaced that and 4x4 is back.

i still love the simplicity of my 86 fullsize, you pull a lever and turn 2 dials on the hubs and it just works

 

Yeah give me an old NP 205 or 208 and locking hubs any day of the week. electric 4x4 Really?
Would it really kill ya to pull a lever, ok yeah auto hubs can be nice but i like simplicity.
Thats what used to be great about working on chevy's everything was simple.

 

Well today a buddy of mine was scraping a 99 blazer ls 4x4 2 door and i took the 4 wheel drive control buttun, and the computer out of the kick panel and those are going to be my first things to swap out to try and I am also going to check the vacumm lines on the transfer case the vacum actuator underneath the battery IS WORKING i can hear it, this morning it would not go into 4x4 at all! I had my wife tap the kick panel with her foot, and poof into 4x4 it went, I will update later on my post, I also have another post not related to 4x4 posted about putting seats from a 99 blazer ls 4x4 2 door (front seats) into my 98 blazer, my seats are part electric these seats are not at all, I would like to use my electric controls in the Other seats if possible is this feasable or am i hit? thanks

 

So update on the 4x4 problem, I went to go pull my module off out of the kick panel and noticed that it was not plugged in all the way it was partially unplugged, I am thinking this is why my issue of it going into 4x4 etc was an issue, Kept the computer close by to see if it clears up the issue tested it after replugging it back in and it was working fine if it acts up again i will replace the computer

 

Anyone know the autozone part # for the vacuum switch on the transfer case? tryn to find it on there website cant find it

 

A little late but here you go:
Four Wheel Drive Actuators at AutoZone.com - Best Four Wheel Drive Actuators Parts for Cars, Trucks & SUVS

 

Wrong, that is NOT on the transfer case.