Things That Whirrr And Go Thunk

Well, I love the AV. I take it in for service in a couple of days. However, two things worry me. The first is that between 45 to 60 mph their is a whirring noise coming from the front of the truck. It is almost like a transmission differential whine but my truck is 2WD. The second is a "thunk" that takes place under the hood when I cut the AC on after a cold start. However, if I just leave it on and cut the key off, it doesn't do that when I start up the truck cold the next time.

Everything else is okay and I don't know whether to say anything to the guys at the shop or not. I figure they just might screw things up. Anyway, just wondering if anyone has any ideas.