Engine vibration

Hi, I have a 2004 td5 defender 90. I get a strong vibration through the hole vehicle when I accelerate above 50mph in 5th gear. It seems to be connected to engine speed not road speed because I get it in 4th gear about 40mph as well. I've changed the propshaft UJ's just to rule them out, but its not made any difference. Has anyone got any suggestions what I should check next. Thanks

might be missing on one cylinder, is it down on power?

I've only had it for a couple of months it was like this when I bought it. I don't know how much power it should have but it seems to pull ok. It runs smoothly at lower speeds it just kicks in at about 50mph. would it smoke if it was missing on one cylinder? because it does'nt.

Wheel bearings, unbalanced wheels, steering damper etc


Edit, read it wrong thought road speed was the thing. You checked the mounts ? Or the other rubber mounts in the drive train just incase ones somehow worked its way loose, unlikely but you never know

Take the visc fan off and the run the car