Gearbox whine advise

S2 V8 manual 116k and the box has a bearing/gear whine in 5th only and only when torque applied - guess its the gear.

Question is do they all do this and box will go on for ever or is it box out and a rebuild soon. Level of noise isnt that bad. Sounds similar to my Saab 900 gearbox when the pinion bearing was shot.

all R380 boxes are noisey, some louder than others, it'll probably go on like this for ages