Noise from gear box on Ford 7740 sle?

With my 92 Ford 7740 SLE each time you release the clutch there is a loud noise sounding like its coming from the gear box. Is used to only make this noise when you would take off in a high gear with low rev, but now its every time you release the clutch. The Clutches C3 & C4 have been calibrated regularly. Does anybody know how i could mend this problem?

Tom
August 2011