What Do You Think It Is???

[Zilverado]

So I noticed a bit of a noise tonight coming from some where in the drive line - I think. It was a kinda "whirring" or "whining" noise. More noticable while coasting or breaking than accelerating. There was also a little vibration, but I'm not sure that this hasn't been there before.

I was thinking u-joints (rear one is fairly new), but there was no "clunking" when getting back on the gas.

I have a split driveshaft and I know the carrier bearing housing (the rubber part) is kinda worn. I haven't been under the truck lately to check the drive line, and tonight I got home too late to really care - so I thought I'd ask the experts and then go look around when I get the time.

Thanks.