Steering Wheel vibration - gets really bad above 60mph

[Mr. Green]

Nation,

My wife's 2003 Echo has had some persistent issues. We've replaced the right front wheel bearing 3 times now, and the driver side front once.

The current issue is steering wheel vibration. It's hardly noticeable at 40mph, but gets serious around 60mph.

Some things I noticed when I took it for a spin today:

The right front wheel makes a clunk-squeak sort of sound on rough road. It has a looser feel at those times. Sort of like an old truck. Not a peep out of the driver's side.

The steering wheel vibration is not changed by shifting to neutral (it's an automatic). The vibration increases with speed, and is rougher at 50mph coming down on a coast from 60 than it is accelerating up from 40.

The vibration is reduced with slight braking and stops with heavy braking. In turns where the weight of the car is shifted to the right side, the vibration is reduced or stops. When the weight is shifted to the left (driver) side, there is no effect or it gets worse.

Uphill seems to be worse than downhill.

The car does not drift to either side when the steering wheel is released when not vibrating, and doesn't have much wander even with the wheel vibrating.

It does not clunk or squeal when turning or braking.

The mileage is 115k.

I'd appreciate any help you could offer.

Thanks.