It's driving me crazy and everyone thats heard it is clueless.
It's a squealing, rattling sound.
It only does it when there is load on the tranny.
If I am crusing down the hi-way at 60mph, throw it in neutral it goes away no matter what the RPM.
It does it much worse in reverse if I brake torque it to about 1600rpm's.
Im convinced it's in the tranny after checking for exhaust vibrations and such.

 

A long shot here, but maybe it's a balance weight coming off the torque converter (or it's already off!).

I used to have a Rover SD1 3500 SE auto and that started to make ***'s own squeal which got worse with RPM. A balance weight had broken one of its two tack welds onto the converter and was merrily whizzing around scoring the bellhousing.

Best of luck!
Mark.

 

Actually the TC is a brand new vigilante, but I appreciate some feedback.

It sounds like something you'd hear when drive belts squeal or accessory bearings go out. But it's definitaly in the back.

Loud enough to be very noticable over my longtubes and duals in the cabin too.

I saw this recall in the FAQ
Bulletin #: 277142
Publish Date: 10/92
Models: 1984-1993 Firebirds w/ Hydra-matric 4L60/700R4 Trannys
Condition: buzzing noise from tranny at idle (more so when in reverse)
Cause: pressure regulator valve oscillating due to oil pressure instability at lower idle RPM
Correction: a new pressure reg. valve has been made to improve oil pressure stability at lower RPM (part #8684048)
Now my tranny has been rebuilt a couple times now, but if something was done wrong could this be a problem. Would it go away above 3000rpms. My problem really doesn't go away at higher RPM's. Gets somewhat quieter but not gone.
Odd things is other times it won't make the noise at all.

To add even more info if it's doing it bad on accel in 1st gear and say it shifts to 2nd at 3000rpm's the sound instantly gets 90% quieter on the shift