Glad to hear you got it fixed, I'm guessing it's the pinion bearing that was causing your whine, I have a very similar whine as well but I'm going to wait until it gets worst to swap mine out, it's been about the same ever since I bought it almost 3 years ago.
I will be interested in hearing what they say is the actual issue on your old 3rd member, what did you end up paying, if you don't mind me asking?
That being said I hope you didn't use the 27 ft. lbs. for the torque on the axle backing plate nuts, I'm not sure what the actual proper torque is but if you read all the replies in that writeup you would have seen where he was questioned on this, and he thinks it's different for disk brakes and he has drum brakes, might want to check on that if you haven't already because from I read it could be much, much higher torque, around 97 ft. lbs. possibly.