Pinion noise?

I bought a 2006 Dodge Dakota that make a noise that sounds like it comes from the rear end .It can be heard as it shifts to 3rd gear at 37mph to 50mph while giving it the gas and goes away while off the gas. I brought it in under warranty and they rebuilt the rear end . It still makes the same noise and now they say it is normal on this truck .I can’t believe the factory would make a truck with a noise like this .What else could it be? Time is running out on the warranty

Check the driveshaft u-joint(s) for excessive wear.

What kind of noise? Rumble, whine, growl?
Is the current noise the same as the one that led to the rear end rebuild?

If they rebuilt the rear end due to the same noise that is now being claimed as normal then ask to see the submitted warranty claim to prove they even did the work.

It is a whine and only when accelerating between 37-50mph
The noise is the same now as before the rebuild. Truck has 24000 miles

A whine usually points to an improper pinion/ring gear mesh and should have been resolved during the rear axle rebuild; IF the rebuild were actually done and you were not simply BSed about it actually being done.

Considering the symptom is the same now as before I believe I would want to see copies of an approved warranty claim to verify the work was actually done.
There should not be a problem with showing you this if it’s all legitimate.
Any warranty claim must be on file; if it’s not something stinks.

I’ll check this also

I’ll be heading to the dealer again this week
Thanks to all,