Rear Whine...My Fix

I have a rear whine in my car. Mechanic thinks it's the tranny, i have a tremec 3550. the guy i bought the car put used gears to try and save a buck (idiot). i actually paid him to put new gears in it. that's another story for another day.

I think it's the rear. it's gotten worse after installing a rear end girdle with the main cap bolts asa support.

So, not knowing if it's bearing or the backlash etc.. i am having my mechanic rebuild the whole darn thing!! including the Trac lock.

also, i have 3:73's in there now and want 4:10's. it's only a weekend fun car and there is not much difference, maybe 300rmp?

question is, if the car whines in all gears under accel, decel and with the clutch in, it should be in the rear? no? yes?

If not, why would this tremec whine like that? i just changed fluids to GM Synchro. don't know what was in their before. It shifts fine, drives fine, no vibration nothing!

Also, anything else to check??

Thanks

I have the rubber around the shifter and the whole floor is done with dynomat. i would still think it can't be the tranny. It's pretty loud!