Jason Torchinsky:

The truck itself appears to be a Peterbilt 579, most likely equipped with an automatic transmission, because why should Waymo make more work for themselves?
 The autonomy equipment appears to be primarily mounted on a roof rack, which houses what seems to be a central LIDAR dome and four ultrasonic sensors, two at each side, covering front and rear. A radar emitter appears to be mounted low and center on the front bumper.