Whine Under Load

[jeenyus]

This is a tough thing to describe, but I'm going to do my best.

My car gets a high pitch whine when i'm driving under load. Trying to replicate the noise, I've noticed it really only happens when the transmission is under load (i.e. giving it gas while already driving pretty fast or when the transmission is slowing down the car on, say, like going downhill in gear).

I have oil to put in the rear differential, but part of me thinks this is an input/output bearing. Is it possible the rear output bearing (does that exist?) could make this whine? I've replaced the input bearing behind the flywheel so i'm not sure what other bearing it could be.

Thank you.

[D.Martijn]

I have the same noise on my ix touring. Haven't figured it out what could cause it.
I've read that it might be the rear diff; when the load changes, the gear mesh changes causing the whining noise.?

Or it might be a bearing in the T case.