Jerry,
Your 03 Thunder does not have the problematic Meritor ADB brakes. It uses the much longer lasting, but a little more expensive to repair, Bendix disc brakes. The average life expectancy for Meritor ADB brakes on the rear of a Marquis is about 40,000 miles and 80,000 on the front, but it is not uncommon to see the Bendix disc brakes run well over 150,000 miles.
Gerald