U.S. sales of medium- and heavy-duty trucks surged 29.3% in March compared with year-ago as deliveries hit 31,994 units, WardsAuto data shows. This was the best March in seven years as all weight classes enjoyed solid year-over-year gains.

An impressive March performance also pushed first-quarter results to 84,497 units, helping compensate for mediocre January and February sales and the best start for big trucks since 2007.

In Class 8, all brands except for Daimler’s Western Star and Freightliner experienced double-digit gains as deliveries jumped 30.4% to 16,452 units, compared with 13,101 year-ago. Volvo Truck led the group with a 133.9% increase, followed by International, up 45.6%. Western Star was the only brand to lose ground as sales plunged 41.2%.

Through the first quarter, overall sales were up 14.8% on volume of 44,547 units vs. 38,805 in 2013.

In the medium-duty segments, overall deliveries climbed 28.2% with all sectors posting double-digit gains.

Class 7 deliveries rose 24.2% for the month led by Ford, up 95.0%. Class leader Freightliner posted a sales gain of 19.0%, although its share fell to 48.8% from 50.9% a year earlier.

Ford also posted stellar results in Class 6 with sales growth of 91.8%, increasing its share of the segment from 21.3% last year to 28.0% and overtaking International for second place. Class leader Freightliner saw its sales grow 24.2%, however market share fell nearly six percentage points to 36.1%.  Overall, Class 6 was the best performing segment, as sales soared 45.8% to 5,622 units, up from 2013’s 4,003.

Ford and Freightliner were the only brands to post losses in Class 5 with volume down 4.6% and 3.7%, respectively. All other brands reported solid gains, led by Chrysler’s Ram brand, up 101.7% on the strength of the Ram Chassis Cab. Class 5 deliveries were up 13.3%  from prior-year with sales of 4,833 units.

March Class 4 sales rose 40.2% to 1,050 units, compared with 778 in 2013. Class leader Isuzu’s domestic models jumped 45.0% while its import line posted a 44.4% gain.

Class 8 had a 56 days’ supply at the end of March, compared with 68 year-ago. However, inventory rose slightly to 35,722 units from 33,193. There was 75 days’ supply of medium-duty trucks, down from 76 prior-year as the month’s unit inventory rose to 44,772 from 35,355.

In other big-truck news: The American Trucking Assn.’s advanced seasonally adjusted For-Hire Truck Tonnage Index increased 2.8% in February, after plunging 4.5% the previous month. The all-time high was in November 2013 (131.0).

“It is pretty clear that winter weather had a negative impact on truck tonnage during February,” says ATA Chief Economist Bob Costello. “However, the impact wasn’t as bad as in January because of the backlog in freight due to the number of storms that hit over the January and February period. The fundamentals for truck freight continue to look good.”

“Several other economic indicators also snapped back in February” he says. “We have a hole to dig out of from such a bad January, but I feel like we are moving in the right direction again. I remain optimistic for 2014.”