CToney,
The KDP, as we so fondly refer to it as, is the dowel pin that Cummins uses to align the gearcase on the front of the engine for assembly and installation. Apparently, there were a batch of engines that had the bores for these pins drilled slightly oversized and consequently the pins have worked their way out and fallen into the gears in the gearcase; usually destroying the gearcase. I'm not sure how prevelant it is in the first generation engines, but there has been a large number of the 12V engines from '94 to '98(???) and I've even read of a few 24V engines involved.
KDP = Killer Dowel Pin. Even though CAnderson stated that 24V engines didn't have the problem, I don't think that's totally true because there are some people reporting the same thing happening to the 24V's... ..... though it may be considerably less.
Cummins hasn't acknowledged that there was really a problem to speak of, so what would they benefit to change the process they were using. Luckily, TDR member, CPFF engineered a couple of jigs that could be used to prevent the pin from coming out... ... . this works if the pin hasn't worked it's way too far out. Hope that clears it for you, even though this is a layman's version.