Whirring sound in Drivetrain... somewhere.. I think.

hey! so i just bought a 99 Rodeo and love it... it drives great, the engine is good and tranny *seems* good... BUT... it's got this whirring/grinding noise that is constant. There is no shudder or anything on the steering, its just a noise... its pretty loud too. It starts off low pitched and as the car accellerates it gets louder and higher in pitch reaching an really good octave at 30MPH... its a constant build, i can hear the tranny going smooth underneath the noise...

When i put it in neutral while driving the noise doesnt change...when i put it in neutral and turn the car off while driving... the noise doesnt change....

I had a look under the car while it was in neutral, stopped of course..... the driveshaft in the back end doesn't really move, but up at the tranny, i can kind of rattle it, not a deep rattle, just a tinny kind of rattle that sounds like its about an inch inside the tranny... i can see a bearing there, and am thinking it could be that...

any suggestions?

Thanks!

I had a whirring sound too and it turned out that it was a loose heat shield. As the engine revs higher, the resonance made the loose shield buzz even more. Neutral or otherwise...

Good Luck.