when I switch from 4wd high to 2wd, I get a loping tire sound at about 25mph. if I switch back and forth 2wd-4wd it eventually goes away. any ideas? light indicators look normal. I can hear a click when I switch. new tires changed nothing.
this is a 2004 2 dr, 3 button 4wd blazer with about 50,000 miles.I thinkthat 4wd both hi and low work fine.

 

you should be parked when you engage and disengage the 4WD and make sure all 4 tires are the same in size and tread