The addition of the Ram 1500 Diesel has helped the truck gain new momentum in the market.

One month doesn’t a trend make.  And it’s too early to see whether General Motors’ worsening recall problems are having an impact – but for the first time ever, Fiat Chrysler’s Ram 1500 outsold rival GM’s Chevrolet Silverado 1500 last month  to become the U.S. market’s second-best-selling full-size pickup truck.

March also marked the first time since 1978 that Chevy’s big rig wasn’t in second place in the fast-reviving truck segment, behind only the long-dominant Ford F-150.

The numbers were close, Ram delivering 42,532 pickups last month compared to the Silverado’s 42,247. And Chevy can take solace in the fact that it remains entrenched in second place for the year to date, holding a more than 10,000-unit lead over the Ram brand: 107,757 Silverado 1500s to 96,906 Ram 1500s.

But there are plenty of reasons for Chevrolet planners to be worrying. Not only did Ram outsell it in the heavy-duty segment – ¾-tons and above – last year, but momentum is not working in Chevy’s favor. It saw Silverado sales plunge an unexpected 7.6% during the first quarter, though sales did rebound a bit last month, with a 6.8% increase.  But Ram volume surged 25.7% in March, and stands up 24.9% for the year-to-date. The segment’s behemoth, the Ford F-Series, saw sales gain 5.1% in March and 2.7% for the first quarter.

(March sales thaw out after winter’s deep freeze. Click Here for details.)

Chevy is still in roll-out phase with the heavy-duty versions of its Silverado.

The Ram 1500 has clearly benefited from the redesign that helped it win kudos as North American truck of the year in January 2013. And it has gained even more momentum with the addition of the high-mileage Ram 1500 Diesel that won it additional honors as 2014 Motor Trend Truck of the Year.

What’s gone wrong for Chevrolet? While some critics faulted the Silverado remake for its conservative design it nonetheless took 2014 North American Truck of the Year honors, along with a number of other awards.  But Silverado is still in launch phase after a complete makeover for the current model-year. And Chevy is just getting out there with the 2015 redesign of the Silverado Heavy-Duty models.  There’s also the disturbing – for GM – possibility that the maker is taking a shellacking as a result of its ongoing ignition switch scandal linked to at least 13 deaths, suggests website PickupTrucks.com.

(Click Here to check out the latest coverage of GM’s ignition switch crisis.)

Curiously, though, sales of the sibling GMC Sierra 1500 pickup gained 22.0% in March, actually gaining momentum compared to a 3.5% gain for the first quarter overall.

While Chevy may be spending time watching the rearview mirror lately, all of the Detroit brands have reason to celebrate.  They continue to maintain a massive lead over the two Japanese full-size pickup wannabes.

For the first quarter of 2014, Ford sold 173,358 F-Series trucks. That’s nearly twice the sales of all Toyota, Nissan and Honda pickup sales combined – including both full-size and midsize models.  The best-seller for the Asian makers was the Toyota Tacoma, at 35,229, while its big brother, the Toyota Tundra managed only 27,402 sales. Tacoma was actually down a bit last month though the redesigned 2014 Tundra did pull off a 25% gain for March and was up 16.2% for the quarter.

(Ford investing $500 mil to add new EcoBoost V-6 for F-Series. Click Herefor the story.)

At the back of the pack, the Nissan Titan generated just 3,318 sales for the quarter, a 35.1% year-over-year decline.

While Nissan might not be celebrating, the industry as a whole can’t be anything but pleased with the performance of the generally high-profit full-size segment.  Truck sales helped pace the overall industry recovery in 2013 and are generally running ahead of the market’s anemic performance so far this year.

“As dealerships thaw out and people start spending more time on dealer lots, we can expect more good news as full-size pickup sales continue their steady climb,” noted a monthly analysis by PickupTrucks.com.

What could make things all the more interesting, meanwhile, will be the launch next autumn of two new midsize pickups from General Motors, the Chevrolet Colorado and GMC Canyon.  Many analysts believe those new offerings could help revive a once-huge niche that has been in decline for the last two decades.