47769

part number 47769 is missing

47769 is the bushings that support end of the slide pins in the mounting. There are actually two different bushings 47769-50020 is plain and goes in the upper position, 47769-50010 is grooved and goes in the lower position. They will go the wrong way round but you would have to really force the grooved bushing into the upper position because it's slightly bigger. The picture is the lower pin and grooved bush.

25528

Without these bushings you could get a single knock just as you apply the brakes or maybe even a series of knocks if the disc is slightly warped and is dragging at the pad. Doubt that it would be strong enough to be described as a "bad knocking" though.

Source: http://www.soarerworld.com/forum/archive/index.php/t-31933.html