Hopefully i can help..
Does the vibration stop above this 70mph speed and below?
Can be felt through the whole car or just through the steering wheel etc?
The vibration stops below 70mph but don't stops above 70mph. Can be felt on the whole car.
Hi..there thanks for getting back..
Ok..It seems you have basically covered all the common areas to check anyway - however one thing to maybe rule out depending on the type of rims you have - if alloys then it can be quite possible for the alloy to buckle slightly and thus cause this sort of vibration through the car,alloys can tend to buckle through either hitting potholes at speed or bumping up kirbs etc can all be factor in causing balance problems,it not to uncommon for that to happen,rare as it is it still can happen so something to bear in mind - balancing wont generally help to solve that youll need to check for any possible run out on each alloy to see wether that is an issue or not - You dont mention wether "all" wheels had been re-balanced - if you only had the fronts done then it would of been wise to do the back too as any unbalance there can tend to cause this through the body of the car if the wheels on the back are un balanced etc...Another cause can be due to a problem with the drivetrain system/suspension bushes/engine/transmission mounts etc ie:- drivetrain either failing bearing/wheel bearing/cv joint/or a possible internal fault with the transmission most of these need to be physically checked and feel for any sort of movement excess inc the suspension to be ruled out for any movement aswell as any obvious issues as per mounts etc as observing and listening wont really get to the route cause especially getting it to the point at which the vibration starts on a lift would be highly unsafe..I would certainly ensure the alloys all 4 if fitted be checked anyway for any "possible buckling" if the rears havent been checked or balanced then it maybe worth having those ruled out too..I do hope this helps..