Gearbox Noise

[willis 18 1 Cars]

I have a BE3 gearbox fitted to my 1990 1.6. I have noticed it sounds like it is rattling/knocking when idling in neutral. When I put the clutch fully in it goes. The gearbox works well, it is smooth and never jumps out of gear.

 

Is this likely to be the thrust bearing or something more?

 

Also, completely unrelated to this but I've just had an old large bore full exhaust, scorpion I think, taken off and had a standard one put on. I thought my valve stem oil seals needed replacing as it was smoking once warmed up but now this issue has disappeared! It also idles much better due to increased back pressure I guess?

 

Thanks