Greetings, I have had a similar problem when going on the highway. When I drive 50 and below...no brake shudder, but when I go on the highway above 60 for a few miles...brake shudder. I went to the dealer and they said I had warped rotors because of the pads sticking in the anti-rattle clips. So, to save a "brake service fee", I took the brake calipers off myself and cleaned with a small wire brush and apply anti-seize on the the slides where the pads are in the caliper brackets. Also I took the wire wheel on my grinder to the ends of the pads that go into the slides to clean off rust and material build up. No more problems. This must be done every 20,000 miles or twice a year for me. I do the backs and fronts when I do my tire rotation or when I put on or take off my winter tires. Each time they were starting to be sticky in the slides. I think the design promotes a build up of material that needs to be cleaned off the slides to allow the pads to release after a brake application.