Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of auto parts-maker American Axle (NYSE:AXL) were stuck in the mud today, falling 10%, after its earnings report didn't make the grade.

So what: Debt refinancing and restructuring costs drove the drivetrain manufacturer to a loss for the quarter but, even without those costs, it only earned $0.07 per share, well off of analyst estimates of $0.33 per share. Revenue, on the other hand, grew 8.5%, to $702.9 million, beating estimates. American Axle sells a majority of its products to General Motors (NYSE:GM), its former owner, and is trying to diversify its revenue streams, and sales outside of GM grew 14% in the quarter. CEO David Dauch blamed the shortfall on "lower capacity utilization resulting from planned customer downtime."

Now what: The auto industry has struggled in the third quarter along with many other cyclical businesses, and it's not surprising to see American Axle come up short. Investors will certainly want to keep an eye on its debt burden, which is up nearly $1.6 billion, but with a P/E of just seven, this could be a good bet if the economy picks up. Keep an eye on GM, as well as a proxy for American Axle.

Need to stay on track with American Axle?

Jeremy Bowman owns shares of General Motors. The Motley Fool has no positions in the stocks mentioned above. Motley Fool newsletter services recommend General Motors Company. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.