Got a bit of a strange vibration started on the Car and i'm looking for idea's on where to start looking.
It only happens every now and again when on a Motorway at about 70 - 75 ish MPH.
Vibration sounds quite fast as in wheel / speed fast, is quite loud but Steering Wheel doesn't vibrate etc.
If i back off then the Vibration stops and it doesn't happen every-time the Car is driven at that speed.
Did a 40 Mile run at 70 - 75 MPH the other day and it was perfect.

Things checked so far are :
Under Trays and Wheel Arch liners checked for security. Found a few screws and nuts missing so have been replaced
Wheels and Tyre's changed for a different set. New ones were freshly balanced before fitting
4 Wheel Tracking checked and adjusted as all 4 Wheels were slightly out.

Took the Car out yesterday for a quick run to check and the Vibration is still there.

I have read on here about Rear Brakes binding and when i got the Car in July, Passenger Rear Caliper was sticking, so both Calipers were stripped and rebuilt with new Seals and Pistons etc, so i don't think it's that.
Also had new Discs and Pads, Front and Rear, at the same time.

Car is a 2011 4.4 TDV8, any idea's as it's driving me nuts.

I would have guessed it was the rear calliper until you said it was stripped and rebuilt already. Saying that I went down the route of just getting new ones just to avoid the chance that there is something else going on there.

it is hard for other guesses, but perhaps the drive shaft isn't balanced anymore?

Must admit you've got me wondering now as the Calipers were done just after i'd replaced a Front Air Bag.
As the Vibration started just after the work was done and because of the way it sounds, i assumed it would be a Undertray or Wheel Arch Liner that i'd not gone on quite right.
Calipers were stripped because the Nearside had a seized piston.

I had a strange vibration in mine turned out to be the wheel bearing moving in the hub ( it had been replaced with an aftermarket changed to original and all good) As far as callipers go replaced mine on the rear with new as had problems refurbing so it could be that as it is intermittent

A few suggestions..

Servotronic valve - experienced intermittent vibe/ buzz only at speed.. Valve was failing
Rear and front sub frame bolts and main bushes (rear)
Once had a hard to find vibe on the rears. Turned out it was the abs reluctor rings breaking up and coming loose
Wheel studs and brake disc screws
Wheel buckle
Crap tyre brands - impossible to balance
Diff mounts, transfer box mounts etc

Good luck 👍 ----------------
2010 RR tdv8 3.6 ( gone but not forgotten ...)
2012 RR tdv8 4.4
2004 RR 4.4 V8 (M62) -gone but not forgotten (sob)
1998 P38 RR - least said the better
2009 BMW 7 Series 3.0d
Various motor cycles - BMW GS
1998 Jag XKr 4.0 V8

Thanks for all the suggestions guys, will have a good luck and report back

Worn drive shaft , as you apply power it settles in an unbalanced position ie slightly out of alignment and vibrates . When in no power position its free to move and align in a different position may be the correct one or again out of alignment and it vibrates .

Well fitted 2 new rear callipers this afternoon.
Did about 30 moles at 70 - 75 mph and all was good, until the I went round a sweeping Lefthand bend and the noise came back again.
Didn’t go away until I slowed down to approx 60 mph and the car was on the straight again.

So I guess it’s not the Rear Brakes.

Meant to ask is it a vibration as in seats vibrating or a rumble as in a noise? If it is a vibration and you feel it in the steering wheel its front if you feel it in the seat its rear

It’s a noise that can be heard quite loudly.
Don’t really feel anything out of the ordinary through the Seats or Steering

I had a similar situation after changing a wheel bearing on the rear it was an aftermarket one and it moved in the hub but only between 55 to 65 in my case new hub and problem gone might not be your issue but it might be again no vibration but noise

I would have thought a wheel bearing has gone, pulls out of the bearing race in a long slow bend at speed, I have had the same one a couple of cars and all 3 times it was the bearing.

Thanks for all the suggestions guys.
Ended up replacing Upper and Lower Front Arms and the lower ball joints on both sides as they were an advisory on the last MOT but TBH they didn’t seem to have allot of play in them.
Whilst doing these I found a broken Front Height Sensor on the Divers Side.
This made me wonder if that was my issue as the Vibration noise usually started on a lefthand bend, which meant it started when the Weight shifted over to the right.
Anyway 2 Days holiday taken to do the work and on Sunday after an initial short test i took on a 180 mile round trip most of which was Dual Carriageway and the Car performed beautifully, no noises what so ever.
( Nearly drove myself mad as I was Hyper listening mode for the entire trip)
So touch wood, I think I’ve fixed it.
My thinking now is that as the weight transferred over to the right the Stability System went mad trying to adjust itself but couldn’t because the broken Sensor meant it had no idea what the Drivers Side Front Suspension was doing.

Excellent news, and something new learned . Cheers ----------------
2010 RR tdv8 3.6 ( gone but not forgotten ...)
2012 RR tdv8 4.4
2004 RR 4.4 V8 (M62) -gone but not forgotten (sob)
1998 P38 RR - least said the better
2009 BMW 7 Series 3.0d
Various motor cycles - BMW GS
1998 Jag XKr 4.0 V8