Yeah, they check all my fluid levels because I get the oil changes done at the Dealer... the tech put a note on the invoice saying I'm missing a front diff-o-ring... I booked it in for my mechanic to take a look at, he's a driveline/front-end specialist. I'll update with the solution when/if it gets fixed.

Dropped her off this morning to get looked at...

Got a call from my mechanic, said he thinks it's a wheel bearing that's starting to go, but it's not bad enough yet for him to know which one, he can't feel it when it's up on the stand (GM Goodwrench certified Front end/suspension/driveline specialist who recently quit the dealer.) He greased my U-joint and replaced my DIFF fill plug gasket. All is well and the next thing for me to tackle is a Tune Up.

Thanks for the help.