My truck has started to whine or howl. It has just over 12,000 miles on it. The sound comes through the floor so it is difficult to pinpoint the exact location, but I suspect rear end. It is not a high pitch whine, but more of a lower tone almost howl sound. I don't hear it when I am under acceleration, but when I let off the gas and coast I will hear it if I am above about 35 mph or 1000 rpm. The pitch of the howl gets higher with higher speeds. I don't hear it when I first start driving it for the day on my way to work, but a few miles into it once the engine is up to normal operating temperature.

My biggest question is does this howl or whine indicate damage being caused, or is it really more of an annoyance. Or does it signify a bigger problem? I have read on this board that the only fix is an entire new rear end. I am taking my truck in later down the road to get some paint blemishes fixed under warranty and can ask them to fix this as well. Is there a TSB out for this?

Thanks for the help.