Just looking for a little help, I have a vibration that starts at around 40mph and goes away as I speed up. I have already replaced both my front and rear drive shaft with the one offered by lucky8 about a year ago, have always greased them and only have about 6k miles on them.

Could this be tires they are relatively new ko2's...

 

Have your tires balanced. My 03 had the vibration around 30-35 and my dads had it around 40. I needed a new driveshaft and his was tires not balanced. Since you have a new driveshaft I would get the tires balanced first

 

You had better lube the drive shafts.
One of those could be dry from lube simply gone.

I had such a problem.

After I pumped in lube / grease the problem went away.
And I drove many thousands of miles afterward.

https://www.flickr.com/photos/76579732@N07/

Bad drive shaft is sort of like a humming vibration.

If your wobble or vibration is affected by braking then it is probably a tire out of balance.

You could move tires from front to back and see if the vibration changes locations.