It's been a decade since General Motors last introduced a new full-size truck. Given the sizzle in the North American truck market, a decade between generations has come to look like an eternity.

Depending upon the source, GM's 1999 full-size truck program is identified as either delayed, greatly delayed or not delayed at all. It doesn't much matter. In the 10 years since GM's last new full-sizers were launched (as 1988 models), the truck market has blown through the roof. And domestic rivals Chrysler Corporation and Ford Motor Company both have taken choke holds on the segment by timing the introduction of their new entries.

Chrysler's all-new Ram (1994) and Ford's redesigned F-series (1997) both made demonstrable sales gains over their predecessors, and the portion of those increases that didn't come from an expanding segment came mostly at the expense of GM. So whether by accident or corporate ineptitude, the GM trucks come at a time to make GM the last of the Big Three to introduce a substantially new truck to customers who've been all but insatiable for the last three years - and conditioned to expect great new product.

It's up to GM's 1999 Chevrolet Silverado and GMC Sierra to reel in the competition. All that's on the line is a stake in the segment that GM says represents an astonishing 45% of the world's total light-vehicle sales.

Powertrain powerhouse. Ford and Chrysler will definitely trail the General. GM powertrain engineers have cranked out their own iron-block version of the Corvette's LS1 OHV V-8 - an engine that (loosely) traces its roots to GM's original four-decades-old small-block V-8, but with dramatic upgrades that make the design perhaps as good as an overhead-valve engine will ever get.

There will be three versions of the new V-8, all continuing with the Vortec name: 4.8L, 5.3L and 6L. The current-model V-8 gasoline-engine lineup includes a 5L and two 5.7L variants.

Trouble for the competition comes when it's time to match horsepower. GM's 4.8L makes 255 hp to the Ford 4.6L SOHC V-8's 220 hp. Jump up to GM's Vortec 5.3L, a displacement where both Ford and Chrysler have entries, and the new GM engine's 265 hp drubs the 235 hp available from Ford's 5.4L SOHC V-8 and the 230 horses found in Chrysler's 5.2L OHV V-8.

Finally, the new 6L Vortec delivers 300 hp. Ford's tiring 5.8L OHV V-8 is good for just 210 hp, and Chrysler's 5.9L V-8 makes 245 hp. That's 90 hp over the Ford and 55 hp better than Chrysler. The base engine remains a 4.3L OHV V-6, with power and torque similar to Ford and Chrysler V-6 base engines.

Manual and automatic transmissions are revised for increased longevity and performance, and in the case of the 4-speed automatic, a special feature permits trailering in overdrive without annoying gear "hunt."

Whopping torque from the new V-8s completes the package for class-leading hauling prowess.

Well built. GM has hauled out some solid construction techniques for the foundation of the new trucks.

A new hydroforming process for the front frame rails and engine crossmember ensures much more accurate dimensional placement of critical mounting brackets and suspension pickup points. The entire frame was wisely designed in a modular, three-piece strategy that permits more efficient assembly of a wide matrix of truck wheelbases, drive configurations and body styles. That should simplify assembly and enhance build quality.

Compare the new frame of a 4-wd extended cab model to its current counterpart, and you'll discover a 2-in. longer wheelbase, wider front and rear track and significant improvements in torsional and lateral rigidity.

Sophisticated styling. Given the success of GM's current styling, the new sheet metal should be well received.

Neither the Silverado nor the Sierra is styled as gregariously as the Ram or as fine-tuned-aggressive as Ford's F-series, but longstanding GM truck buyers won't be disappointed by decent freshening of the previous-generation styling. The chromy, bass-mouthed Sierra will help in establishing GMC's hoped-for upscale brand image, and it's for buyers who want a style with a little more daring.

There's little doubt the increases in cabin volume will be welcomed by today's size-obsessed truck buyers. There's 2.5 in. more space from the front bumper to the back of the cab, 3.1 in. for extended-cab models. Headroom is increased by a half-inch or more, which GM says will lead the class.

GM also says rear-seat legroom will beat both Chrysler and Ford full-sizers - yet the early press materials indicate the new GM trucks lose 0.4 in. of front legroom and 1.6 in. of rear legroom to their predecessors.

There's an all-new interior, too. Floor height is lowered 1 in. The instrument panel is cleaner, with typically clear GM dials and materials that look just plain durable.

Unfortunately, GM engineers forgot a door: Extended-cab versions of the truck will come with just three doors. The Ram and the F-series can be purchased with a second door on each side, opening opposite the front doors.

"There was a lot of debate about that," says one development engineer. "We probably should have gone ahead with four doors." One gets the feeling GM product planners either hadn't identified four doors as a competitive necessity - or the feature was deemed essential too late in the development process to be engineered in time for the launch. A serious miscue.

GM finally has done the right thing with brakes, however. Disc brakes all around are standard equipment, the heart of a system GM engineers say is the first-ever GM brake system designed specifically for a truck platform. All models get twin-piston front calipers; the rear calipers on 1500-series models are single-piston units, with twin pistons also fitted at the rear of the larger 2500 models. Four-wheel ABS also is standard.

Engineers played a video dramatizing the stopping effectiveness of the new brake components. It appears GM will be second to none in the increasingly critical area of braking effectiveness.

There is a wide selection of bed sizes. There are more usefully placed tie-down rungs and accommodation for modular sectioning system to tailor the bed to your needs.

Affordable to own. Generously equipped full-sizers are now fetching more than $30,000. The new GM trucks surely will be priced similarly. However, GM is providing no firm price structure at this time.

On the operating-cost side, low owner maintenance is promised with 100,000-mile tuneup intervals and new dual-accessory drive belts that are designed to go 150,000 miles. For more information on the Chevy Silverado, circle 202; for the GMC Sierra, circle 201.