New Vibrations - CLS

[6cyl]

Strange one this - I'm getting a vibration around 70mph. Got the wheels balanced twice, at different establishments. Problem gets worse, the vibes now start at 60mph.

Not related to braking. (Brand new discs and pads all round 3 months ago, 4500 miles ago).
Steering wheel doesn't shake much.
Whole car shakes.

The speed it starts shaking seems to vary, sometimes it starts at 60, other times past 65mph.
Car has airmatic. Mileage is 95K. I've had the car
There is an intermittent shake at idle.

Tyres visually checked for bulging etc no problems, tread is 2.8mm at the back, 5mm at the front. Tyres are Goodyear F1 asymmetric 3, dated Dec 2016.

I can't categorically say it's not the wheel balance, but it has been balanced twice and it doesn't feel like it's wheel balance at the front wheels, as I've experienced it and it is much more obvious.

What do you guys think?

 

[whitenemesis]

Whole car shaking is usually the rear tyres/wheels
Have you checked for buckled wheels?
Check propshaft centre bearing?
Engine and gearbox mounts?

 

[6cyl]

Not sure how to check the propshaft centre bearing, would this be a visual and big screwdriver levering check for worn coupling?
The engine and transmission were changed about 25K miles ago, though it doesn't mean they haven't worn or leaked in that time I guess. There is a slight vibration at idle.
The tyre depot didn't mention the wheels being buckled, but looks I need to check.

The problem started suddenly.

 

[Abb]

I would have all your mounts checked, my money would be on the engine ones.

 

[6cyl]

Ok - took the car in, everything looked ok on inspection including with the persuasion bar. I was advised that it could possibly be the centre prop bearing, which looked ok. I authorised the work, when it was removed the bearing itself was smooth, but the bearing housing had deformed by about 5mm. A new one was duly fitted. I have tested it at speed and it seems to have fixed it. I'll try it on a longer journey to confirm. The slight vibration at idle is still there. They reckon the engine and gearbox mounts are fine and not collapsed.