weird problem, maybe tranny? Options

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okay when i first bought it, it was quiet. i drive about 30-50 miles a day to work and school..oil still good and changed every 2.5-3K miles. fluids all still good and full. here's the thing: when im gearing into second gear and when it engages right then, it makes this woosshhhh sound..only if i go slowly it makes the noise but when i accelerate a little quicker it rarely makes the noise. it makes that noise everytime i let go of the gas petal when im in gear and letting the speed drop slowly. it only happens when engaging into 2nd gear and on all gears when dropping speed without touching clutch of switching gears. is it because of tranny? do i need to flush my tranny liquid? this is weird. maybe some of you guys might have this but sheesh when i first bought it, no noise, very camry-like. hehe help!