Found the source of a vibration that has annoyed me for some time now, and it was thanks to a Mk3 2000E Cortina that I used to own!
This vibration started at about 70mph and you could sometimes drive through it at 80mph, or you sometimes couldn't! I'd looked at the usual prop joints, mounts and practically everything else - then I remembered the Cortina!
On these, there's a split propshaft, with a centre bearing and doughnut. The two lengths of prop join in the centre of the doughnut with a male/female joint, and a rubber sleeve in the join. On the Niva, there's a similar system in the intermediate shaft between the gearbox and the transfer box. On taking this apart (T/box out!) it appeared that the rubber washer and cup were too soft, so I renewed them. Result - vibration gone!
I think the doughnut controls runout until 70ish mph is reached, then centrifugal force takes over, causing vibration. That's the conclusion I came to with the Cortina, and replacing the same parts cured it there too!
As I said, may be of no use but, you never know!
Regards,
