1995 Mustang GT, Trans knock/rattle in Neutral.

[schultz11]

I just bought a 1995 GT 5spd std. While in neutral or driving at low speeds, there is a knock or rattle coming from the transmission, But when driving faster, or cruising on the highway, the sound goes away. I figured maybe something with the clutch, but the previous owner says the clutch was just replaced.

Thanks.