As Doug wrote on yesterday, General Motors Corp. (NYSE: GM) again reduced plans for truck production for the third time in the last month and a half yesterday, which tells me that the road ahead for the automaker in one of its most profitable vehicle lines is not going to be smooth at all. The automaker already told the world about reducing production at six U.S. plants, and now newly stoked fears about a slowing U.S. economy has the automaker in a whirlwind about possible truck excess inventory. How is one of GM's best-selling lines just sitting idle on dealer lots across the nation?

It's like this: demand creeps downward and the automaker reduces production in order to balance existing and in-work inventory with dealer sales expectations. Nothing new there -- but in this case, it's a staple of GM's entire lineup, not some odd-designed passenger car that did not take off with consumers. Did GM just try to stuff the dealer channel with more profitable vehicles here, and it finally caught up with them? Is the company's truck marketing failing somehow? To see GM's idle truck-building capacity like this is very strange.

Let's go further: does GM continually see U.S. truck sales declining over the next few years? While rightsizing is probably the correct thing to do here to some extent, where is the slack demand for pickups falling? To the competition's trucks or to larger cars and SUVs? That question depends on whether GM sees retail or fleet sales dropping (or both). Once the conference call to cover August U.S. sales happens next week after the holiday, we'll form a better picture then on what is inside GM's thinking here. I'll be liveblogging it this Tuesday at 2pm EST, so stay tuned to BloggingStocks at that time.