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 vehicle manufacturer Navistar (NYSE: NAV) are at risk of getting a speeding ticket today, with shares zooming higher by as much as 11%, after the company reported the best annual results in years.

So what: Fourth-quarter revenue added up to $4.3 billion, with earnings per share of $3.37. The figures were mixed compared to the consensus estimates of $4.45 billion in sales and $3.08 per share in profit. The full fiscal year posted the best earnings since 2008.

Now what: The fourth quarter marked increases in worldwide unit charge-outs in North American and global businesses. Throughout the year, Navistar also repurchased roughly 2.7 million shares of its stock, and is on track to finish out its $175-million stock-repurchase program in early 2012. Navistar CEO Dan Ustian also hinted that the company may collaborate with rival Oshkosh (NYSE: OSK), saying that it "might be beneficial for everybody." Activist investor Carl Icahn has sizable stakes in both companies and has been pushing for a tie-up.

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Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. 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.