The wheelstud clips are an idea, but it should have vibrated since day 1 if that's the problem.

I'd be inclined to look at driveshaft & u-joints. Remember driveshaft rpms depend on wheel speed, not engine speed, so the OD shouldn't make a difference.

If the OD does make a difference then the issue is probably engine-speed related instead of driveshaft related... but your symptoms seem to match vehicle speed not engine rpms.