2000 Grand Am GT wont shift into fourth

My wife's 2000 Pontiac Grand AM GT wont shift into fourth gear and it makes a hell of a whir when in motion. It seems to shift from 1st to 2nd to 3rd smoothly, though the whir gets louder as the gears progress.
Any ideas?
Pat
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4th gear hub is stripped out. Trans will need a rebuild.
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