Sadler, who is making his first start for Joe Denette Motorsports in the series, turned a lap at 122.607 mph around the half-mile, high-banked track. It was his second pole in his 18th truck start. He started on the pole and won at Pocono in July 2010.
Harvick will attempt to win his third consecutive truck race, while Busch will try to win at Bristol for the fourth year in a row. Harvick won earlier this month at Pocono and then last Saturday at Michigan.
Points leader Johnny Sauter will start 12th. Sauter currently holds a five- point advantage over Buescher.
Jennifer Jo Cobb and Norm Benning failed to qualify.
The 200-lap truck race at Bristol is scheduled to start just after 8:00 p.m. (et).