I have a 1999 Blazer 2dr 4wd with about 64k miles on it. Ever since the first day I bought the car about 7 months ago, I have had a reocurring problem when I am traveling at more than 40mph in 2wd. I will be driving and out of no where it will start making a high pitched grinding/squealing noise almost like the sound of gears not meshing correctly. As soon as I drop below 40mph the sound stops but the car slams into 4wd, or if I manually turn on the 4wd the sound immediately stops so I know it has to do with the 4wd. Is this a problem with the transfer case/front differential itself or is it just a vacuum switch problem? Has anyone ever had this problem before? I have been having to drive in 4wd to keep the noise from happening which I know is not very good on dry roads. It also really makes tight turns hard. Thanks.

 

Can't say for sure, but mine did about the same thing with around 72,000 miles on it. It would make a grinding/squealing noise but it was going any faster than 25-30 mph. Never tried anything with the 4wd so that I am not sure on either. But this was shortly before the tranny grenaded itself. Lost reverse and it shifted really hard after that. Had to have the whole tranny replaced because the gears had basically ground themselves smooth. Might be a place to start, can't say for sure though...
Hope this helps a little! Best of luck!

 

do u feel any vibration on the steering wheel? also does it stop when you slightly turn right or left? the other thing what kind of transfer case do you have 4 buttons or 3?

 

99LS4x4ryanlw: Thanks....not really what I wanted to hear since trannys are kinda expensive. But I am happy to know that it has happened to people before, so someone out there has to know the problem. I thought it was tranny at first also, but once I could stop it by switching to 4wd hi I ruled that out...I guess that might have been a mistake. Thanks for the input!

Onder: It does not stop when I turn the wheel slightly, but I do have a slight vibration in the wheel, actually the whole car for that matter. I just figured it was because I need an alignment and tire rebalancing. I have the 3 button transfer case, with 2wd, 4wd hi and low. Do you think that this could be an electrical problem? Thanks for the input!

 

Most likely the vacuum switch on the driver side of the transfer case is stuck allowing partial vacuum to be applied to the front axle actuator. 15 minutes of work, under $20 in parts: Buy Dorman - OE Solutions Motor 600-500 at Advance Auto Parts____ Pull the switch out, the spring loaded ball should move freely, if not, that's the problem.

 

I thought i had a problem with my vacuum switch too but what i did before i started working on it is, i put the car on jack stands so the 4 tires were off the ground. i asked one of my friend to watch the tires when i switch from 2hi-4hi-4lo and then i saw that i dont have any problems. you should figure out where is the sound coming from. it might be one of your you joints. before you star replacing parts figure out what is your problem.

 

You can test the switch by installing a vacuum gauge on the vacuum line at the front axle actuator, (under the battery). Make sure you're in 2WD, drive 70mph, if it has an automatic trans, shift to 3rd gear and coast down to about 20mph. The vacuum gauge should remain on zero the entire time. For the amount of work involved in doing that, you can pull the switch and physically check it in far less time, and if it's bad, you already have it out

 

Ok thanks I will have to try that. I will probably just physically check it.