I have a 1999 4dr Blazer that should have 4wd but for some reason it is not working. I am not too handy when it comes to fixing mechanical things myself I am more of an audio guy myself. But my problem is this.

When I press any of my 4wd options (4hi,4lo,4auto) I first leave the vehicle in park or neutral and press the button. I hear something moving in the internal parts of the vehicle but the front wheels will not spin on any mode. The light also blinks when they are pushed only the 2hi button will stay lit. Not a big problem since most of my travel is on the streets but with 5 inches of snow that came overnight I am stranded at the house lol. Anything you guys could suggest would be the fix would help a lot since the last time I took it to the only shop around here who deals with chevys somehow turned a routine brakepad change into costing me a whole new transmission. I would very much like not to repeat the same thing anything specific that I could tell him? For the record I know he is a lousy guy but he is the only guy in the area who can fix my baby.

 

Is the "Service 4wd" light illuminated on the dash? If so, you will need a GM Tech2 or equivalent scan tool capable of reading serial bus communication devices other than the PCM (EBCM, BCM, TCCM, SRS module, etc).

There are some things that you can check though. When you put your truck into one of the 4wd modes (4HI/4LO), the electronic vacuum solenoid on the firewall near the distributor will open up supplying vacuum pressure to the actuator under the battery. If this does not occur, the TCCM will not see that the front axle is engaged and will then fail the shift.

Start with that and let us know how you make out.

You might also want to read through a few of the 4wd related articles in the Tech Article (DIY) section. While not all of them will apply to your truck, the operation of the 4wd systems, specifically the front axle engagement, is very similar for all 4wd s-series trucks.