The perils of selling primarily to one buyer were apparent today in Visteon's (NYSE:VC) third-quarter results. The auto parts company used to be a part of Ford (NYSE:F) and is still heavily dependent on it for sales. As Ford's fortunes go, so go Visteon's.

Given that, it's not surprising that following Ford's announcement yesterday that its North American production fell 17% in the third quarter, Visteon posted a wider Q3 loss. The company lost $168 million, or $1.34 a share. In the same quarter last year, Visteon lost $52 million, or $0.40. In the current loss is an after-tax charge of $41 million, or $0.33 per share, for bonuses under a recently ratified contract with the United Auto Workers.

Visteon's sales dropped 11% to $3.9 billion. The company, which is attempting to broaden its sales base so that its fate isn't so tightly tied to Ford's, made progress in that regard, with 26% of its revenues coming from non-Ford sources, up from 21% in the prior year quarter.

Not all auto parts suppliers are suffering, though, which underscores further the dangers associated with too much reliance on one customer. Smaller auto parts company Lear (NYSE:LEA), for example, contrasted Visteon's dire results by posting higher sales and earnings. Lear, which makes interiors for cars and trucks, netted $76.1 million, up from $61.6 million.

Granted, some of that was because Lear shifted the timing of some restructuring expenses from the third to the fourth quarter, but the company still held up better than Visteon. Sales rose to $3.5 billion from $3.3 billion.

BorgWarner (NYSE:BWA), maker of power train equipment, has also done well over the last year. The company, whose products help boost efficiency and reduce emissions, was recommended by Tom Gardner for the February 2003 issue of Motley Fool Stock Advisor. The stock is up 43% since. BorgWarner reports its third quarter results on Monday, Oct. 27.