Cadillac CTS-V - Whine, is it the diff?

I have a whine coming from under my car. You hear it at any speeds above 30 mph and only when I'm off the gas. If I give it any amount of throttle the noise goes away. Doesn't matter if the clutch is pressed or depressed. It gets louder the faster I go. Does this sound like the diff problem? What actually goes wrong in them, is it the bearings? It almost sounds like the backlash of the ring and pinion is bad. Can you rebuild the diff? I don't really have at least $1000 to buy a used one and hope it does not whine. When I bought the car the previous owner said the diff was replaced under warranty with the latest one.

Usually diff whine in these cars is under light acceleration in higher gears between 45-70mph. Your noise sounds like it could be from somewhere else, but it could be difficult to tell without actually hearing it in person.

Could be the carrier bearing also. That's a annoying whine from the center of the car. Most people who notice differential noise are usually in 5th or 6th gear when it starts. But at 30mph the best thing I can tell you is that most likely it's the carrier bearing. Located in the driveshaft

I hope its the carrier bearing, you can change that by itself right? The weird thing is that is goes away as soon as you touch the throttle at all. I think if it was a bearing it would be doing it all the time.

As far as I know the carrier bearing is not serviceable... yet. The current alternatives are either a stock replacement driveshaft or an aftermarket driveshaft that eliminates the stock style bearing.

But regardless that's a strange issue. I've never read/experienced that kinda thing before.