My 2000 s-10 Blazer's 4wd isn't working. About 2 months ago I used my 4wd, for the first time of the year. Then shortly after, I started hearing a high pitched humming sound coming from the front passenger wheel. I would hear it while running reg 2wd.This sound would go away if I pushed my 4wd Hi button, but would come back immediately after turning it back off. Just recently the sound went away completely.

Today I noticed the front wheels weren't spinning as I was trying to make it up my steep hill. The switch on the dash showed that it was engaged but that clearly wasn't the case. My dad is going to look at it but wanted me to do some reading on it first.

Any help would be appreciated.

 

Sounds like you have a vacuum problem since that is how the front axle engages. My 2000 did something very similar and it was the vacuum switch located on top of the transfer case.

If that isn't the culprit, the next thing that I would check would be the actuator under the battery tray. When you shift into 4WD the transfer case allows vacuum to go to the actuator which in turn pulls a cable engaging the front axle. If the actuator has a tear in the rubber part or something it won't hold the vacuum required to engage the front axle.

If that isn't the problem, you may have a vacuum leak somewhere else, but I'm willing to be the problem lies somewhere in the two components mentioned.

Good Luck!