So i picked up an extra tcase thinking that mine is going out. It has a slight whine only in 1st and 2nd gear when accelerating or engine braking. It does not make any noise when in neutral at any speed.

It doesnt sound like this video at the high speeds.
I have a TRE built 5 speed with the 4:11. I was thinking it could be the trans since it only happens in gear

Maybe its on its way out? Im not sure.

It has 140K miles on it. Tons of racing was done on it, drag, road course, auto x and never had a problem. I change the fluid 1-3 times a year depending how much i drive it.

Any ideas or other ways to check whats going on?

 

Evos whine in first and second, especially first. Your stuff is likely fine..