Hi, Did the whine disappear after replacing just the bearing near the 4 gear sprocket? Mine is making a noise in 3rd and 4th also (you can check my video), and would love to have it fix your way without taking out the gearbox.
Mine made a whine only in 3rd and 4th too im not sure which is the 4 gear sprocket, i just changed them all. it was definitely this wear on the bearings that was causing the whine though cos i tried changing just the small ones at the end case first and it did not get rid of the whine.
