Your correct on the way a crawler typically steers. That said, like another post stated, if the machine will push and spoin the tracks, and come to a complete stop when the clutches are released, then the chancees of the problem being in the clutch is next to nothing. If your problem is with the machine turning, and the brakes are tightened as tight as they will go and still don't hold the track for you to make a turn then the brake is the problem.
That said, I've never seen a steering clutch setup that didn't have to come out in order to remove the brake band. If the clutches on your machine are hydraulicly released then you'll be money ahead to replace the seals in the release pistons while you have the bands out. Good luck and keep us updated on your progress.