If when cruising at roughly 50MPH, you can change the volume of the whine and make the noise almost disappear with an extremely light touch to the throttle, then I'm going to say pinion bearing.

 

No disappearing at letting up.
So i will have to take off that newly sealed differential i guess? To see carrier bearing.?
the one in auto stores looks like it mounts on the outside. Shaft.
looks wet there also..but maybe from draining the fluid earlier.
Nothing seen anywhere or anything like the part in store-it mounts outside the diff..I have base model an 1 solid piece on shaft

 

I did find that front drivers side lower ball joint- that dreaded recalled one - needs changing.
on the 3 oclock an 9 oclock there is some play on tire an a tiny bit at 12 an 6..
Can that be the culprit?
Im still wondering where this carrier bearing is on my dakota .

 

Front bearings being bad will generally change tone/volume when changing direction.

Carrier bearings are on the sides of the differential carrier. The part the ring gear bolts to.

 

You got a pic?
What do I need to do to get it off?

 

Your pic. That's the carrier there. Need to pull the axles, then those four bolts and out it comes. Bearings are under the caps.

 

So are the blue arrows pointing to the pinion bearings.Is the carrier way up in the front red arrow where the entire differential gears gotta come out to get to it? Crazy design .



can you post a pic of one...

 

Blue arrows are the carrier bearing caps. Pinion is what provides power to the ring gear. (the driveshaft attaches to it) Carrier is what you see there with all the gears.