Ok, here's a good one. I've got a '93 S10 Blazer with the "W" code 4.3. I've had it for a few months, but have only had it on the road for the last couple weeks. I noticed a buzzing sound from under the front of the vehicle, kind of like the sound heavy treaded tires make while going down the road. I figured I had some type of CV joint going bad. When I got it, the previous owner said the 4 wheel drive worked, but I got nothing when I shifted from 2 wheel to 4 high (Manual transfer case). Well, the other day my 4 wheel drive indicator came on, along with a locking thud sound, and the buzzing noise went away. It's still in 2 wheel drive. Today as I'm driving, the buzzing was back, the indicator was off. At the first stop light, the locking sound came back, light came on, no more buzz. It does this on it's own. And it doesn't act like it's in 4 wheel drive when the light's on. I'm at a loss... Oh, and the buzzing sound seems to quiet down when I'm on the gas. Any ideas?? Thanks in advance!!

 

Seeing as you have a manual transfer case it sounds like it's only partially engaging. I'm not familiar with those but my '80 sierra grand 4x4 had an issue like that with manual hubs, until I replaced then Warn manual hubs I think. Check fluid levels & cable etc.

 

the hubs on yours are going to be automatic. even on the 93s the 4wd drive maybe a lever but its actually ran off a actuator (normally under batt tray) and those are so common for failure 90% of the 4wd i see that dont work or have issues is because of the actuator.
i live in wisconsin and see all the diferent seasons and it wreaks havoc in those actuators. good luck

 

Chadillac is correct. The first thing I would suspect on your Blazer is the vacuum actuator under the battery tray. There's a large vacuum diaphragm under the tray which is connected to a vacuum source from the transfer case and it controls the cable which locks the front differential output. If it's not completely engaging or releasing it can cause that buzzing sound.

Pull the battery and tray and check the vacuum actuator. Make sure it's fully engaging and releasing. I suspect it's not.

 

Thanks for the advice. I pulled the battery and checked the actuator and it seemed like it had fully released the cable. I was able to pull the cable out toward the actuator and heard what sounded like something moving in the transfer case. I tried to push it in and it didn't budge. Inside, without the motor running, I moved the 4 wheel drive shifter from 2 to 4 wheel drive and heard a similar sound. But when I drove it, the 4 wheel drive light was on. I don't know if it means anything or not, but I can't get it to shift past neutral into 4 low. Is it possible that the light is just on, because I don't get any jolting when I turn, which makes me think the front wheels are moving freely. Someone told me I could take that actuator off, pull the cable out and clamp it but I'm afraid that would damage something.

 

thats kinda of helpful but always remember their ran off vacumn so one pin hole can affect it. with the vehicle off its not running any vacumn threw the acuator so hence forth hard to determine just by feel. but ur buddie is correct you can bypass it like that but spend the time to make sure were ur put clamp at that transfercase is in correct position and that there will no longer be shift on fly 4wd.
but in my cases ive just replaced it and had no issues with 4wd working for me

 

Ok. I asked about clamping the cable because the cheapest actuator I've found in my area is about $50 and I don't have the money right now to spend on it. I'm not too worried about the 4 wheel drive right now, since we're (hopefully) past snow season. Like I said before, it doesn't seem like it's running in 4 wheel drive, even with the indicator light on. I know it had been wrecked at some point before I got it and a lot of things weren't repaired right. (I have two zip ties holding my radiator to my core support!) It's a work in progress, but so far, I like it!! Thanks for the advice!!