Has anyone had problems with the front and rear drive gears on the 4wd Tahoe? I had to get mine replaced 1.5 yrs ago (GM paid even though out of warranty). The dealer said the Auto 4WD wasn't very functional and was like driving in 4WD. He said he has seen a number of gear replacements. Now -- I only use the Auto 4WD on rare occasions (snow/ice). Just last week, my front gears started whirring again. Any experiences like this would be helpful. I'm going to push GM to pay, if it is the gears.