Have you ever driven a long way in reverse?
I have a vague memory of a Welsh Trial probably early 1980s when I had to reverse back down a section where I failed at nearly the top. The transmission locked up. It wasn't the nut you talk of, but the one inside the TT that hold the pinion bearing in place. It could have the same effect though.

Well, yes I have Alan. Often do on trials but I've been doing that with this exact rear axle for over 20 years (although with its earlier Torque Tube) and no previous problems.

Something else to check when we get home for events in the future.

Steve

Location: North Yorkshire

Alas, we do a fair bit of reversing on trials!

There you go, you see. It was unusual for me.