Second the comment re only engaging under load. StableLoad installation instructions suggest sawing off a corner of the angled rubber block if need be to ensure you don't have continual engagement. If you don't cut them eventually they will wear down (after a whole lot of squeaking, don't ask me how I know). If you've got the right part number for your truck they should be close but not hitting. If in doubt, call Tork Lift tech support and they can tell you how much (and where) you can cut or belt-sand for a bit of ride tuning. Good folks.
duncan