Morris Minor Owners Club

I note a spate of gearbox threads at the moment, but here's another one...
Box is generally good and smooth. Oil is clean and at correct level. 1st, 4th, and reverse all perfect. 2nd and 3rd select easily and properly, and do not jump out, BUT 2nd and 3rd have a really bad and quite loud whine. Obviously I'm going to have to strip the box sooner or later, but can anyone suggest what I'm likely to find? Thanks.

Damaged teeth on the laygear?

Damaged needle rollers and shaft supporting the laygear -causing it to run slightly out of mesh.......and so damage the teeth. The sooner you deal with it - the less the damage will be.....