Transmission knocking - guidance sought

[Roland Alcock]

As clutch depression makes no difference, I would be suspecting crown wheel and pinion. Been there twice before. Its strange how back axle noises travel forwards up the car and appear to emanate from where it does not....

Roly

[Parazine]

I'm with you Roly, also been there and done that!

[Ivor Hawkins]

Take the box for a little run and before taking your foot off the gas gently hold the handbrake and feel if the knocking comes up through the handbrake lever...if you can feel it, I bet the nuts on the coupling are hitting the handbrake mounting and you'll see the witness marks when you crawl underneath....after you've stopped of course!

[Phil D]

I think Roland and Parazine have it. Took the prop shaft off (getting it clear of the fabric coupling's tricky!).
On gentle rotation of the rear joint I could feel resistance at one point which took effort to force it past. I'd had the same on my Austin Ten a couple of years ago, so now suspect crown wheel and pinion. I can see at least one defective tooth on the crown wheel, although there was no debris in the oil when drained. At this point I shall use a trusted supplier.
Thank you all for your help. For those less mechanically experienced it's reassuring to have such willing advice.