02' zr2 4 wheel problems

02' zr2 blazer 76,000 miles 4wheel not working. at a dead stop i'll push 4hi and i can hear some switch sound like it engaged and SOMETIMES it will go in smoothly, i'll take off driving with it engaged and working great and it will disengage at any random time by itself. when i try to go from 2hi to 4hi while driving it will most of the time make a crazy winding and grinding sound, then i'll be scared out of my mind and immediately push back to 2hi and it goes away. but sometimes going from 2hi to 4hi while driving it will make no sound and not engage and rarely it will make no sound and engage, not for long though, it never stays in long at all. but most of the time it doesn't work, it's very unpredictable.

i've changed the actuator under the battery and the little i think it's called vacuum switch on the transfer case (it's a nut lookin thing with a plug on it). still having the same problem.

what on planet earth is the problem with this beast. it's been two rough winters with no 4 wheel and i really don't want to go though another. actually i got some new crazy winter/mud tires and i don't really even need 4 wheel but I WANT IT BACK SO BAD!!!

PLEASE HELP nobody else seems to no what the prob is and i really don't want to take it to the chevy dealer

Welcome to AF

The problem needs proper testing to find the problem.

First we need to know what transfer case you have?
233 or 236?

Does you shift buttons have a AUTO button?
Or just 2W -4W 4L?

Have you checked for codes?
Have you checked wiring and for good engine vacuum to front axel?

i'm not sure if it's a 233 or 236 but i'm gonna go find out soon and check all the wires and hoses that i can. it is a 3 button switch no auto, i have not checked for codes don't know how. i don't really know much about fixing cars and all that has to do with the 4 wheel drive on this vehicle but i know i can fix it if it just requires a new part. i'm gonna go check what model transfer case it is and check hoses and wires and look for some other switch i heard about on the firewall soon here, thanks for your quick reply

i'm not sure if it's a 233 or 236 but i'm gonna go find out soon and check all the wires and hoses that i can. it is a 3 button switch no auto, i have not checked for codes don't know how. i don't really know much about fixing cars and all that has to do with the 4 wheel drive on this vehicle but i know i can fix it if it just requires a new part. i'm gonna go check what model transfer case it is and check hoses and wires and look for some other switch i heard about on the firewall soon here, thanks for your quick reply

The 2 button no auto is a 233 transfer case.
Id tag is on back of case.

On the 233 ground pin 13 on diagnostic connector and turn key on and watch shift button shift lights.
If the come on for bulb check and turn off the electronics is good.
if the start flashing codes and repeating code you have a problem.
post back the flashes on buttons.

Also make sure the front actuator is getting good engine vacuum and locking in front axle good.
This link may help.
http://www.automotiveforums.com/vbulletin/showthread.php?t=572914

Get us know what you find.

The actuator seems to be working fine but it also doesn't look very straight. I don't know if this matters or not, but it's always been like that I guess. The transfer case seems to be covered in some kind of oil. I'm guessing it's from the transfer case. Maybe that's my problem?? I don't know what ground pin 13 on diagnostic connector means or if I have that or what. If you want to explain more in detail to me, I'll see what I can do or do I need to take it to someone that has something like that? I'd change the transfer case oil but I have no idea how to fill it up. Where do I fill it up and how do I know how much to put in there? http://i288.photobucket.com/albums/ll198/swreety7/DSC00258.jpg?t=1227829752

http://i288.photobucket.com/albums/ll198/swreety7/DSC00259.jpg?t=1227829868

http://i288.photobucket.com/albums/ll198/swreety7/DSC00249.jpg?t=1227830097

http://i288.photobucket.com/albums/ll198/swreety7/DSC00253.jpg

Does the actuater pull the cabel all of the way to lock in front axel?
Is it getting full engine vacuum to it?

I don't know does it look like it's pulling in all the way from the picture to you? How do I tell it's getting pulled in all the way? The 4 wheel drive engages like 50% of the time from a dead stop and in this picture I engaged the 4 hi at a stop so I'm assuming it's pulled in all the way. What about the oil caked all over the transfer case? I also noticed that the grinding and winding sound is coming from under the passenger side feet area

I can not tell for sure from the picture.
It does look a little off set.
With 4W engaged see if you can pull the cable any more.
And T in a vacuum gauge and tape it to windshield check for full engine vacuum on it with 4W engaged on a pull or load on engine.

It could be losing vacuum on actuator and letting it kick back out or not pull cabel all of the way.

Is the oil on transfer case or front rear end?
Is it fresh oil or old stuff?
What color is it?
Is anything low on oil?
How is all fluid levels?
Good Luck

well after trying ever part that has to do with the four wheel drive and having no solution, the only next option was a new transfer case. Well i got one used for $150 ( can you believe it) and it finally works again, it's so nice to have four wheel drive back in the terrible new york winters, though it hasn't really snowed since i fixed it, and now i want snow. the mechanic that did the work took apart my old transfer case and their was a bunch of little broken peices of metal in their and he showed me all the broken parts, it was pretty ugly. it's so nice to have it back, thanks for all the help. now i have to go over to the pontiac forums to see why my girls cars windshield washer system stopped working