Well, I've been told by two different people that it's a throw out berring. But I'm not a mechanic.. It is a definite knocking noise, but not like a lifter knocking, much faster knocking than that. It goes away when I put my foot in on the clutch(it's a 5 spd.) and sounds the worst in 1st, 2nd,3rd,and 4th. You can still here it in 5th, but it's not as loud. When I purchased the car I was told it had a noise in the tranny, but I got it for a good price, so my intention was to fix it in the future. Does any of that help?