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 & Manufacturing (NYSE: AXL) sank 10% in intraday trading Friday on extraordinarily high volume.  

So what: At the time of publication, nearly 5 million of American Axle's shares had been traded, versus the three-month average volume of 2.6 million shares. American Axle didn't release any news today, but when you couple the stock's soaring price over the past few months with today's letdown from big customer Ford (NYSE: F), a heavy pullback shouldn't come as a big surprise. 

Now what: Fools might do well to stay on the sidelines for now. Even with today's double-digit pullback, American Axle shares are still up more than 100% from the 52-week lows they set in early July. And when you throw in the fact that American Axle's total debt-to-capital (187%) crushes that of large auto-parts plays like Johnson Controls (24.7%) and Magna International (1.5%), the decision to stay away seems that much easier.

Interested in more info on American Axle? Add it to your watchlist.

Fool contributor Brian Pacampara owns no position in any of the companies mentioned. Try any of our Foolish newsletter services free for 30 days.

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