Broken motor mount
 

So I was at my dealer to get the oil pan gasket replaced on the 2009 Hybrid Tahoe because it was seeping a bit and making a mess of the undercarriage and the old timer mechanic found the driver side motor mount was snapped clean in two.

I asked to see the problem before authorizing replacement and sure enough it was broken in two. It physically looked fine with the weight of the engine holding it down, the only way to diagnose it is to open the hood, start the vehicle, shift from park to drive to reverse and watch the engine. It shouldn't move at all, mine lifted about 3-4 inches in drive(driver's side mount), didn't move at all in reverse(passenger side mount). after replacement the engine doesn't move one bit.

I asked the mechanic how he suspected it broke and he pointed to a shopping cart full of broken ones off Phoenix Police PPV Tahoe's, he had changed about 10 that week and was intimately familiar with the issue, he said they all break.

He said on a Tahoe with 100K miles it's pretty much guaranteed the driver's side mount is either broken or completely worn out on the verge of breaking.

The symptoms were very subtle and I attributed them to the vehicle getting old, some clunking and creaking(now completely gone), I actually suspect it has been like this for a while(50k+ miles) and this is the first astute mechanic that was familiar with this issue.

Thankfully the passenger side didn't also break because the engine being completely loose in the engine bay probably wouldn't have been good.

Very easy to check, open the hood, run through the gears(with your foot on the brake-lol), if the engine rocks a little you have a worn motor mount, if it rocks a lot or lifts, you have a broken motor mount.(there's a video on You Tube)