Depends exactly what you mean by vibration. A continuous vibration dependent on speed is, if at the rate of wheel rotation, most likely an out of balance tyre. If it is at prop shaft rotation rate, it is most likely a worn universal, or possibly the prop shaft has been incorrectly assembled, or it is the result of a suspension lift.
On the other hand, if you mean an oscillation after hitting a bump, this will be due to inadequate damping in the steering. I think this model does not rely on damping at the swivel, although loose swivel bearings will cause it, so the steering damper or its bushes or any of the steering ball joints would be suspect.
John
				
			 
			
		 
			
				
			
			
				John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
			
			
		 
	
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