06 TD4 FL1 - Noise and vibration at 70mph

Hi all
Bought a 2006 FL1 yesterday and noticed on the way home that I could feel a rotational vibration and droning noise coming from the rear of the vehicle at pretty much bang on 70mph. The droning noise seems to get louder the faster you go above 70mph. Drop below 70mph and both seem to go away.

The rear tyres are more worn than the front and would need replacing in the next 3-6 months would be my guess.

Is the droning and vibration likely to be down to the worn rear tyres? or something more sinister such as rear diff or VC?

All help would be greatfully received!

Many thanks

Mark.

Newest or larger circumference tyres always need to be on the rear else you'll goose the rear diff and ird.

Thanks for the reply.

It is likely that the damage has already been done to the rear diff etc? Drives perfectly up until 70mph.
Could the noise and vibration be caused by the lower rolling radius on the rear?
I guess the first thing to do is swop the tyres from back to front to see if the noise and vibration go away?

Hi , i had a drone at 70mph , cause was mismatched tyres , take the car for a 5 mile run then get under and feel your VCU { CENTRE OF PROPSHAFTS } if it is very hot i would change all 4 tyres same make/model/size , and hope your vcu has not been killed after changing my tyres , my vcu was cold after a run , and no more drone hope this helps

I'll give that a go and hope for the best. Thanks for the reply.

Update.

New rear tyres going on today to see if this eliminates the droning noise.

Felt the VCU this morning after a run to work. It felt warm to the touch, but not hot.

New tyres on and the noise seems to have gone, thank god! Still quiet noisey but i'm putting that done to the width of rubber 245/45/18.