06 E-250 Noises/Clunk in first/reverse only
 

215k

Transmission is making almost a whirring noise when in 1st that goes away when it shifts to 2nd. Sound matches road speed, not engine speed. Almost sounds like a bad fan clutch, but the sound goes away if I rev in neutral or any other gear.

Also, in reverse, it will make clunking sound, especially when picking up some speed.

Drives fine in other gears/at highway speed

Do i need a new transmission? Anything else I can check before replacing it?

Before spending a lot of $$ you may not need to do, why not have someone check the drive line U-Joints.
With that many miles and if they were never replaced, might be the only thing wrong.