Hi there. My 420GSi engine is generally very smooth and even sounds great on full throttle… but at 65-75 motorway speed there’s vibration in the cabin with a bit of a drone. Engine super smooth at 60. It has new gearbox and front mount, not new d/s mount (couldn’t find one) so I just wondered if “they all do that, sir”? Matthew

Hi, sounds like it could potentially be something as simple as wheel balancing, I would definitely start here, if that doesn’t fix the vibration a drive shaft is another potential cause.

Also worth checking if a tyre is out of shape. Jack up each corner in turn and spin the wheel, watching for a "rise & fall" in tyre tread. A saw tooth type feathering of the inner/outer edge of the tyre tread can also cause a drone & vibration.

Lost count of the amount of cars coming into the dealerships I used to work at with complaints of wheel bearing failure, which turned out to be a tyre out of shape. Budget tyres & Pirellis particularly prone!

Thanks gents - it’s definitely engine speed rather than road speed that’s the issue - just over around 3200-3500 revs. Do others with a 220 or 420 get this sort of drone type vibration. It’s not a severe vibration like you’d get with a bad tyre, it’s really more an annoying noise and you can feel it if you put your foot on the on the floor of the car. Just makes long journeys a pain. It’s always been like this in all fairness.