4 wheel drive not working

#1

why does my 98 chevy blazer shift from 2 wheel drive in to 4 wheel drive while iam driving??

#2

How do you normally shift it into and out. Is there a lever or a switch?

#3

This may be vacuum activated like earlier models. If there’s a vacuum leak it may be causing the vacuum activator to switch it into 4wd without you activating the lever.