vibration

[Al Housman]

I recently replaced all 4 rear cv joints and when I took the truck for a test drive all was good until we got to about 45mph when a rumbling/vibration sound started up.  I put it down to new cv joints bedding in and, having just done the fronts cvs (syncro) took it for a good spin and it's still there. 

This could all be coincidence and I will be double checking cv bolts and prop shaft as well as tyres but is there anyone out there who has had similar and might share their experience.

I did try coasting out of gear down a long hill with the engine off an there were no unpleasant noises so I think everything is reasonably well lined up  in the drive shaft department.

I don't know if the noise will go away above 55 since I almost never get up to that speed!!
Thanks