I admit it, General Motors, you surprised me.

This isn't the story I expected to be writing today. Today's article was going to be about how Ford (NYSE: F) finally, after oh-so-many years, wrested the U.S. sales crown from GM in March once and for all.

Ford's on a roll, as we all know, with great new products and a comeback story that's earning admiration all over the world. I expected March -- a wild sales month, or so we'd been hearing -- to be the month when Ford blew past GM once and for all.

That's the story I figured I'd be writing today. And indeed, Ford had a great month. It wasn't quite up to the overheated predictions we'd been hearing from Edmunds.com and other industry watchers, but it was excellent by any measure, with good news from all corners of the company (aside from the about-to-be-dumped Volvo).

But here's a wrinkle I hadn't quite anticipated: GM had a big month, too. And here's another: Ford's great month wasn't even enough for second place.

Details and devils
Ford certainly turned in big gains -- a 29% improvement over February, and a nearly 40% gain over the we're-all-doomed month of March 2009. As I said, those weren't unexpected; March saw the start of Toyota's (NYSE: TM) all-out incentives-fueled effort to regain its standing in the U.S. market, and the resulting discounting frenzy was expected to drive strong gains for well-positioned players like Ford and Hyundai.

But GM, it turns out, isn't dead yet. The much-maligned (in some quarters, anyway) "Government Motors" turned in its own impressive performance, with a fine 34% increase over February and a 43% gain over March 2009, when GM -- and much of the rest of the civilized world -- appeared on the edge of collapse.

I keep using the word "impressed," and, yeah, GM, I'm impressed. But I have to say I rolled my eyes when I started digging into the company's press releases. GM doesn't break out retail versus fleet numbers as well as I'd like in these monthly things, but they do drop some hints -- hints like "Buick: total sales up 76 percent; retail sales up 34 percent," and "Chevrolet: total sales up 41 percent; retail sales up 24 percent."

Fleet sales are an eye-roller because they tend to be low-margin bulk sales to basically captive markets like car rental companies. They don't generate tons of profits and they don't really help us understand how well a company is competing in the marketplace (unless that company is Hertz (NYSE: HTZ), Avis Budget (NYSE: CAR), or Dollar Thrifty (NYSE: DTG)). GM's hardly the only offender on this front -- Ford's press release notes in passing that "March retail sales up 38 percent; fleet sales up 53 percent" -- but I can't help wondering how much of GM's sales increase was market enthusiasm versus a corporate push to eke out enough sales to stay ahead of Ford.

As it turned out, they managed to stay ahead of another juggernaut as well -- barely.

Toyota isn't dead yet, either
GM might have surprised me, but I did expect a major comeback for Toyota, driven by an unprecedented incentives and marketing blitz. So I can't say I was surprised to see a big month from the Japanese giant -- a 40.7% increase over March 2009, and a spectacular increase of nearly 87% over February.

How spectacular? Spectacular enough to put Toyota just a little bit ahead of Ford for second place in the U.S. market, and just a little bit behind GM (when including discontinued brands). But given that fewer than 5,000 vehicles separate GM from Ford, I wouldn't put too much stock in this pecking order. It's fair to say that the three are running neck-and-neck-and-neck, with no clear leader (yet) emerging.

The rest are just the rest
I've always had a soft spot for Chrysler -- America's scrappiest automaker -- but "soft" is how its sales looked, down 8.3% from last March as the company continues to fall further from America's radar screens. Chrysler's history is a long string of colorful near-death experiences followed by dramatic comebacks, but I really wonder how new owner Fiat is going to pull this one out.

And the others? Nissan had a fine month, with a 43% increase over March 2009; Hyundai was up a solid 15%, not bad but less than some had anticipated; Honda (NYSE: HMC) saw a 18% gain; there was a ho-hum 2.6% gain from BMW (including Mini); and Daimler's (NYSE: DAI) Mercedes-Benz turned in a solid 28.3% increase.

There are a lot of interesting subplots here, and I'll be looking at several of them in coming days. But one thing's for sure: This drama ain't over.

Read more about the ongoing automotive shakeout:

Fool contributor John Rosevear owns shares of Ford. You can follow his Foolish twittering at @jrosevear as he continues to sort through the ongoing global auto shakeout. Ford Motor is a Motley Fool Stock Advisor pick. Try any of our Foolish newsletters today, free for 30 days.

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