survey steve

bit of a strange one,
when driving from cold, ie first thing in the morning, theres a vibration comes through the car, but it's not coming through the steering wheel.

There was an issue before with the drivers side rear hub being a bit loose and had a couple of split discs on the brakes giving the front a bit of a hard time of it till they were replaced.

I've had the geometry and wheel alignment done twice and it's still there, have also checked the wheels for balanced, no issues.

You only see it at about 50 mph and again at about 70 mph, below these theres nothing
It's not a huge vibration, but it's very noticeable, was wondering if this could be a bearing or diff issue ?

Any ideas ??

Cheers

Steve