1995 Maxima GLE Tranny Noise?

I own a 95 Max and recently it has started making a grinding noise
under strain and heavy acceleration. The noise almost resembles a
vibratin/grindin as if something was loose. The worst part of this is I
have taken my car to the nissan dealership and to three different
service centers for opinions spending a total of $765 for everyone to
tell me there is nothing wrong with the car that they could find. The
gentleman at the Nissas dealership validated the noise stating "I did
hear the strange noise you keep hearing when i accelerated hard" but
assures my the transmission and other parts are "Just fine" Being one
of suspicion and doubt I have the gut instinct there is something wrong
with my veahils. Owners preminition maybe? Either way i was searching
and i came across this NG and I decided since the "powers that be"
evidentaly have no clue about my car maybe another max owner would be
able to share.