like many others my 4wd wont fully engage. its a 2000 blazer LS with the auto 4wd, 2hi, 4hi, and 4lo push button. there is a noticeable clunk like its trying to engage but still its only the back wheels. i removed battery and located vacuum actuator. removed it and found it holds vacuum but was getting no vacuum pull from vacuum line. followed line up to what i am guessing is called a vacuum solenoid. this solenoid has an electrical connector to it which im guessing connects to the 4wd switch inside. two vacuum lines are attached to it. one leading to the vacuum actuator and the other leads into the firewall on the drivers side. here is where i am confused. i read a forum and it said a vacuum line comes straight from the transfer case to the vacuum actuator but did not find any vacuum lines. this vacuum solenoid has a hole on top im guessing to release vacuum once it is disengaged but i could be totally wrong. does my blazer have the wrong vacuum line going to the actuator or is the vacuum solenoid bad. just in case its not a vacuum solenoid ill post the picture ofthe part that the vacuum line goes to from the actuator. snowing in the mountains here and wanting my 4wd all help greatly appreciated!!!

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anyone have any idea if it is the vacuum solenoid thats the problem????

 

In the auto4wd models (NVG236 transfer case), the vacuum line should go to engine vacuum. Some earlier models had this go to the transfer case vacuum switch.

Is there vacuum at the other vacuum line when the engine is running? How about when the transfer case is in one of the dedicated 4wd modes (ie. not auto)?

Is the "service 4wd" light illuminated on the dash? If so, a Tech2 (dealer) or equivalent scan tool is required to access the TCCM (transfer case control module) and read the codes.

 

there is no service 4wd light. i have not pulled the other vacuum line off yet while running. i have pulled it off when engine is off and you can hear a release of air not sure from what though. my guess is the vacuum solenoid that these vacuum lines are going to is the culprit. could it be anything else? i think i might just replace it and go from there especially because it seems that i have to get it through a dealership :-( so i dont know how long that will take. but any other suggestions im happy to hear!! thanks

 

I had a problem with my 4wd for the last 2 years, the firstwinter the dealership took out the transfer case controlmodule and put it back in and it worked for a while, thenlast winter it went again and they replaced it, that cost about $900... that was not fun