98 Pushbutton 4WD engaging on its own at times?

I have owned my 98 4x4 Blazer for about 4 years, and it has done this every year at least twice per year. I will be driving along in 2-wheel high, turn into a parking lot, and try to get in a parking space (or leaving a parking space). At this point, it makes a light whining noise and is hard to turn sharply (even harder than usual) to get in or out of the spot. I look over at the dash, and 4-wheel high is lit up. I have to put it back in 2-wheel and back up for a few feet until it clunks to get it back in 2WD. Everything works fine, but it just shifts itself into 4-wheel high at random times.

This last time I noticed the problem, I realized it always seems to do it when it's been raining for a day or so. Does the Blazer shift into 4WD on its own if it detects tire slippage (like from wet pavement), or something?

I have owned my 98 4x4 Blazer for about 4 years, and it has done this every year at least twice per year. I will be driving along in 2-wheel high, turn into a parking lot, and try to get in a parking space (or leaving a parking space). At this point, it makes a light whining noise and is hard to turn sharply (even harder than usual) to get in or out of the spot. I look over at the dash, and 4-wheel high is lit up. I have to put it back in 2-wheel and back up for a few feet until it clunks to get it back in 2WD. Everything works fine, but it just shifts itself into 4-wheel high at random times.

This last time I noticed the problem, I realized it always seems to do it when it's been raining for a day or so. Does the Blazer shift into 4WD on its own if it detects tire slippage (like from wet pavement), or something?


Do you have a 4WD-Auto as one selection...just curious....

No - I have three square pushbuttons in a vertical row: 2HI, 4HI, 4LO, in top-down order. I keep it in 2HI at all times, but it puts itself into 4HI at random times. If I put it in neutral when it's doing its "ghost shift" thing, it will sometimes even shift all the way to 4LO on its own.

It does it (as I said) about twice per year, and usually when I'm first starting up after having been in a parking spot and sometimes after I've been driving awhile when it's raining.

It did it again yesterday. It was definitely in 2HI, it had been raining all day, and I turned into a wet parking lot. The tire seemed to slip a little as I accelerated into the lot, then by the time I tried to turn into a parking spot, it had put itself in 4HI.

It must be some kind of automatic slip-avoidance feature that isn't in the owner's manual and wasn't supposed to be offered until 1999, when they added the Auto feature. Mine is supposed to be 2HI if I put it in 2HI, but it seems to pick what it thinks works best on its own...