whining/grining upon acceleration

Hey all! I've got a 99 GT (76k miles) - bone stock - that I've not had very long, and I am hearing a pretty loud whining whenever I touch the gas.... (even slightly) - seems to whine less under harder acceleration.... but if cruising down the road in any gear, step on gas just a little and rear end has nasty grinding/whining noise...

from my reading here, I suspect it could be the clutches in the rear end of maybe needs a new ring/pinion? (then I get to go 4.10's!!!!!!!!) LOL - but in all seriousness... how would I go about troubleshooting it.... finding out which specific thing needs the work, the clutches of the gears?

thanks in advance for any help!

ok... thank you for the help! that actually makes me feel better, I wanted gears anyway! - by what procedure can I test this, to be sure that's the problem??
thanks!
Bill

trinity_gt said:

This type of whine from the rear usually points to a pinion bearing issue. When you apply throttle the forces try to push the pinion forward out of the housing, loading the inner pinion bearing. If the bearing it bad, this is when it will make noise.

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Does anyone have a way of describing what the procedure would be for checking to see if this is the problem? (which is certainly sounds like it is)
thanks!