2000 Blazer LS: driven at least weekly throughout the year. Used heavily for two months of the year. Last year I replaced the vacuum unit (under the battery). The cable moved freely.

Today I was cyclingback and forth between4wd high and 2wd. I first worked the buttons while stopped. The minor clunk clunks indicated to me that things were moving and perhaps working. Next, I switched between 4wd and 2wd while driving about 30mph. As I entered the freeway I switched to 2wd.

I drove about 10 miles at 65 mph to the local Lowes. A slow 90 degree turn into the parking area produced a heavy drag/bind at the front wheels. The short of it is that I manipulated the 4/2 switch repeatedly. After a few moments, the bind was no longer apparent.

I then made the return trip home, stopping at a grocery store. I made the same, slow 90 degree turns and there was no drag or bind experienced. Apparently once I got it into 2wd, it stayed there.

I read a posting about different tire sizes causing the problem. My tires are the same size but different brands from front to back. Underinflation does not seem to be in play. Anyone have an opinion?