Expert: Mark Bisig - 1/16/2006

Question
Hello,

I have a 1998 Chevy Blazer LS 4x4 with 120,000 miles on it. I have only had it for a few months and have only recently been using the 4 wheel drive in the lovley weather we have been having. For a short time at first, the drive was working fine. Now, since I've been using 4x4 on and off, sometimes when I start it (In 2 wheel) I'll hear a loud clunk coming from the front right. Then, accelerating from a stop or a slow speed in 4 wheel, it makes this same annoying noise yet again, same location, and repeats while driving. Also, While driving (usually on the highway), In 2 wheel, I'll begin to hear this loud, screaming, almost saw like noise coming from the front right, and the intensity of this noise goes along w/ how fast I am going (slow = low and annoying, faster = fast and annoying). If I put it in 4 wheel while driving, It will stop. Back to 2 wheel again, It will continue until the commute is over. These problems began just after I really started using the 4 wheel drive on and off. Any suggestions? possible diagnosis? This would be greatly appreciated. Thank you very much for your time.

Answer
Hi Tom, The first thing you need to do is replace the transfer case vacuum switch. This switch is located on the transfer case on the drivers side. After you do this you need to make sure the front locks in when in 4 wheel. With all that grinding noise, the shift sleeve and gear in the front axle might be damaged! If it is you will need to have those parts replaced too.

Hope this helps

Have a Great Day      Mark