How much whine is normal for a new sure grip rear end?

Just got the car together and now I am working out all the bugs. I was curious as to how much whine is normal for these 8-3/4 rear ends? I have a rebuilt a body 8-3/4 742 with 3:91 gears with a 4 speed man. I have a very slight whine when I am slowing down that i notice. Is this normal for a low geared rear end like this?
Also at cruising speed in 4th gear I devlop a slight vibration through out the car. I am thinking that it is the drive shaft needs balancing. If it were the drive shaft wouldnt I notice it in the lower gears as well and not just at 55-65 cruising speeds? Thanks