88 N/A Auto trans whine
 

Hello. i was getting sick of the banging and rattling of the rear sub-frame bushings so i temporarily filled them with Norton speed grip structural glue until i have time to put new bushings in, which actually worked quite well for now. but now i noticed the whining in either the trans and/or diff sounds much louder inside the car. i don't see how this can possibly be related but it was literally the first time i drove it after filling the bushing i heard it. could it possibly be because there is no rubber in the bushing(its like a solid mount now) that the sound is resonating inside the car more?... i opened to door and put my head near the bottom of the car and drove and i didn't hear and whining at all/ or do you think its just a coincidence and my trans or diff is about to go.

My 88' Z31 is making a grinding/whining noise and I got it rebuilt 15k miles ago or something. I've been told my bearing is going out as well as the transmission itself. So i'm not really sure about you. Try taking it to an import shop?:036:

Vibration isolation
 

It's seems pretty clear that a solid connection would transfer more vibration and noise, so once you glued up the bushings you eliminated a lot of the play and allowed the vibrations to pass on to the rest of the chassis.