Transmission noise- 98 Civic Ex 5spd
 

Hey there, I'm new to the forums and trying to sell my 98 civic ex because I bought a 08 si, but am having problems selling it due to a transmission noise.

The transmission shifts perfectly, and the clutch seems to be fine also, but I am no mechanic. While accelerating in lower gears and lower rpm's there comes a weird whining or kind of sucking noise. The car is completely stock except for a K&N air filter, the car has never been beaten on.

Any help on trouble shooting or idea on what it MIGHT be? Thanks guys