Powerful vibration through gear knob at speed.

Hi, I have an R reg Fiat Punto S60. At 55 mph in 5th, and under load, a vibration sets up that makes it almost impossible to hold onto the gear knob. Ease off the power - the vibration goes. Change gear -
and ditto. We have changed all wheels and rebalanced. The suspension is checked, the discs and hubs have been checked for 'trueness', the wheel bearings are fine. With the car jacked up and the front wheels turning the vibration can be felt throught he chassis rather than the gear knob. Any clues please?
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snipped-for-privacy@skinnerx4.co.uk wrote:

come down the linkages and thus the gearbox/engine must be vibrating. The fact that the problem gets worse with load indicates that the movement of the gearbox/engine is worst which is exactly what I would expect with damaged/broken/worn engine/gearbox mounts.
I can't remember what the 3 mounts are constructed like but often a simple visible inspection is not enough the diagnose the mounts and load has to be applied. For this a 4 post MOT lift is ideal. With the handbrake fully on and the foot brake firmly applied, select first gear, lift the revs a little and bounce the engine and clutch as though you were doing a normal take off. One can induce short sharp heavy loads and also long straining loads.
You can try this on the ground to check the mounts on the engine (cam shaft timing belt end) and the mount on the very end of the gearbox. However the third mount at the back of the engine, under the floor pan in-front of the gear lever is not easy to inspect from over the top of the engine or from the side of the car. PLEASE DO NOT venture under the car to examine this mount with the method above. VERY DANGEROUS!
Nick /////
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