I just got my 2000 blazer a few months back and when i got it i checked 4hi and 4lo to make sure they worked and they did and still do. But, one time later i tried the auto 4x4 and it was very weird. It was jerking me left and right and there was a knocking noise like it was repeatedly engaging 4wheel, so i pulled over and got out to look around, cause at the time i thought i had a flat tire, and it smelled like burnt rubber. So, i turned auto 4x4 off and havnt used it since then. It seems like there is a bad sensor or something making it go in and out of 4wheel. I was wondering if anyone has heard of this happening.