Why would 4WD just started engaging on its own on 2008 Chevrolet Suburban 1500

While turning sharply, the 4wd engages and almost stops the vehicle. Seems to be fine going straight forward. Selector switch does not change anything. Lights don't blink. shows that it is in 2WD High but definitely switches to 4WD Low when turning sharply.
Safe to drive until we can get to a dealer? Only has 68,900 miles on it

Asked by for the 2008 Chevrolet Suburban 1500
Actually it's stuck in 4x4 'HIGH'and only shows up when turning! Driving straight you don't notice it, when turning sharp on dry pavement, any active 4WD vehicle will feel as if it is binding up or bucking. That is normal operation. The fact it is always in 4WD, is not! Yes it is safe to drive, try to avoid really sharp turns until repaired. Best thing to do is just leave it as it is so mechanic can check it out on a scanner to see what is wrong. In other words don't get to working on it or try to alter the mode it's in now!
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I am having the same problem in my 2007. Only 60,000 miles.
I haven't noticed it on pavement only gravel. I was wondering if you ever found the problem.