Defender vibrations

Right, here goes. Defender 90 1994 vintage has got a vibration through the steering wheel at about 47/50 mph. Wheels have been balanced, swivels rebuilt both sides, wheel bearings done, fairly new tyres as well. Steering ball joints are tight, steering column has no play in it and steering box feels tight. Shocks and springs are all less than 12 months old as well.
Any ideas as to where the problem could be?

propshaft uj's

front propshaft UJ(s), had similar issue.

Front prop has been removed already, still has the problem

Do you mean,it still vibrated when the front prop was removed????
If so,then it can't be something in the front drivetrain.
What about the rear prop???
I had exactly the same thing with my 110 for a whole year.The only thing that stopped it was to take off the front prop and run it in diff lock.
I had done al the things you have done,so the only thing left was the diff.I changed that and it cured the vibration.
Good luck....These things can be a real pain in the arse.

Hopefully not the diff those aren't cheap try wiggling the rear prop if there's play up and down its the ujs hopefully that's the problem ujs are under 15 quid and easy to change

You fitted new suspension by any chance? 2" lift?

Scrawf