Yep - I know where you're coming from, but it doesn't cover the squealing/disappearing with clutch in?
A stuffed layshaft (on its own) won't make it jump out of gear or have any gear selection problems, but will squeal like hell under load - and if it's gone badly enough (and indeed this fault seems to be getting worse) it could be jamming enough to give power loss, vibration etc.
What it
would do though is creat a fair bit of swarf in the gearbox - I think I'd be draining the gearbox oil through a filter to see what sort of solids come out. You always get a little "iron filings" type swarf with these, but anything more than "metal dust" size, and there's something nasty going on IMHO.
Mind you, I'm guessing here too!
Looking forward to knowing the real outcome of this - so sorry for Dru, as either way it sounds a bit on the serious side.
Cheers!
