My '99 V70 has about 77,000 miles. I feel a vibration in the steering wheel which starts at about 68 mph and gets a bit worse at 70 -75. It feels like a fluttering. I'm certain it is not a tire balance issue. Does this seem to be a cv joint problem. No clacking noise at full throttle on turns at lower speeds. If it is what I suspect, is this a premature failure or is it normal at this mileage, most of which is highway driving?

I would reverse the front wheels with the back and see if it changes anything, that we you will quickly know if it is a wheel. If you feel a vibration in your butt after the change then it is a wheel which has now moved to the back of the car. You could then move one wheel at a time to the front to find out which wheel it is. I find my V70 extremely sensitive to wheel balance.

I would check the wheel balancing before you do anything else, since that is the most likely cause of the situation you have described.

It could possibly be a pad catching on the disc, which can be caused by a piston rusting in place and stopping the pad fully retracting.

If you don't have any nasty noises at full lock, it's unlikely to be a cv joint - that's when they normally make their presence felt.

You do not say what wheels you have on your car, if they are alloy I would carefully check them for any damage if the balancing does not fix the problem.
John Scales (850R 1996)