Steering wheel shaking at sixty five to seventy five mph

I have replaced the brakes and the tires, both are brand new. I jacked up the car and checked for play in the wheels, I pushed, pulled and nothing at all, no humming sound on the freeway, no shaking when I press the brake pedal, rotors are good. I checked the bushings for the tie rod ends, perfect shape. No clunking or noise of any kind while driving. Steering wheel shakes between sixty five and seventy five mph, depending on the road, the shaking makes my arm numb after a few minutes. Please help I cannot find the problem.