The 727 in my 79 LRE has been making noise...really quite soon after it was rebuilt.

It started small, and at first didn't think it was my transmission...it'd occur under very light loads/high vacuum situations, so I actually thought that it was noise from air resonating through my throttle plates...as soon as a little throttle was applied, it would go away, and come back under low load/high vacuum situations again.

After taking my Truck to the Drag Strip though, the sound is unmistakably the transmission. It only happens in 2nd and 3rd gear...but has gotten MUCH louder. Sounds kind of like a loud flat horn...

And again, under light load...when I apply throttle, the noise goes away. If I replicate the same throttle conditions/rpm's in 1st, no noises, load or no load. Trans was "built" with components to race (shift kit, race clutches/bands, high pressure regulator spring, etc)

Transmission otherwise drives just fine...no slipping, good firm shifts.