Gear whine?

I have a 2103 trd sport dbl cab v6 w/tow package with 138K miles. I tow a 3150# car on a 1400# trailer and probably load the cab with another 400#s of tools and me...I tow about twenty to thirty days a year on trips some of which are hilly ie NY state and Va.

I found a gear tooth face a couple diff fluid changes back and now have what I think is some rear diff noise.

I'm going to have a shop check the rear and lash etc but wondering if this has been an issue for others and if there is a tougher rear upgrade needed or available.

Thanks in advance and Happy Easter!

PS added airlift bags last year and towing car + trailer since 2017, tow in 4th gear...

 

The ECGS website is a decent place to start research and pricing.

 

awesome! Thank you!