bizarre shifting noise under hard acceleration, ideas?

[goofycarp]

Hi, I have a 70 911t with an alleged rebuild 901 transmission. Under normal acceleration it shifts fine with no noise; however, when under full throtle there's no noise until the clutch is depressed and boy oh boy all hell breaks loose, major noise until goes into next gear. Any ideas about what's going on? Sounds like a really loud clicking noise and sounds like a very spendy fix....Thanks, Cort Chambers.