4spd trans linkage help needed

Well Gents, I am still chasing the loud knocking sound. I just had the rear diff. rechecked by the guy that I bought it from and its OK. He knows his stuff so I trust him. We didnt think that it was the rear diff to begin with, but better to be safe than sorry. That was the last thing that I worked on before the knocking sound started. I checked the front and rear u-joints and they seem to be tight. I had the car in the trans shop and they couldnt figure out what could be causing the noise. But, now I am thinking that they didnt really know how to work on a 39yr old 4spd. So just to re-cap the on-going problem, the car is making a knocking noise in the transmission tunnel when I have the car in any gear and it is coasting (not under gas). When I engage the clutch pedal the noise stops. Could this be the gears in the front of the transmission that are not active when the clutch is locked up? I am not a tranny guy so I dont know what the heck I am supposed to be looking for.

Any additional advice would be appreciated. I will fix this thing whether it wants to be fixed or not!

Thanks again,

Jason
614-946-3333