Strange Vibration

[crazydavez28]

I have heard before that if you have a vibration you can tell what it is coming from by watching small objects in my rear-view mirror.

Circles - driveshaft

Vertical lines - tires

but i have what looks like an upside down 'U' and the vibration comes and goes in phases. moving from rear to front then gone then starts again in the rear moving to the front

It is not a violent shake either I would describe it as medium to slight and I have no issue driving 80mph like this... it just gets really old after 1+hrs on a trip

I have replaced U-joints in the driveshaft (they needed it anyway).

I want to get a good picture of what it may be before I start throwing a lot of money and time at it.

 

[Minion1186]

Can you hear any strange noises at all when driving at speeds above 55? I've been having something like this happen in my salon since I put another rear in it, vibration and a weird vibrating noise at 55-60. My u joints are new as well. Best of luck to you, I'd love to figure this out myself.