Quick-as-a-wink light-truck product cycles are hardly a Big Three custom.

But given the sizzle in the North American full-size truck market, a decade between generations in this segment has come to look like an eternity.

A decade is how long it has been since General Motors Corp. last introduced a new full-size truck. Depending upon whose version you prefer, GM's 1999 full-size truck program - code-named GMT800 - was 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, the truck market has blown through the roof and domestic rivals Chrysler Corp. and Ford Motor Co. both took chokeholds on the segment with new entries - if not deliberately, then at least fortuitously - timed to take advantage of a ravenous market.

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 out of GM's hide. So whether by accident or corporate ineptitude, the GMT800 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. And don't forget a U.S.-built Toyota full-sizer coming in '99.

It's up to GM's 1999 Chevrolet Silverado and GMC Sierra to reel in the competition.

The world at large will get its first look at GM's new trucks at the 1998 North American International Auto Show next month in Detroit; GM gave journalists an early overview in October.

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-truck sales.

GM says, as do so many other automakers these days, that development decisions regarding its new light trucks were driven largely by the "voice of the customer."

GM's vehicle line executive (VLE) team identified eight GMT800 "product goals" that were considered primary customer requirements. We'll let GM structure the remainder of this article, then, by detailing and evaluating the new trucks using the VLEs' eight primary criteria:

n WELL BUILT

Only time can tell. But GM has hauled out some solid construction techniques for the foundation of the new trucks, so if frame "performance" is any gauge of general build quality, GM should be fine here.

A new hydroforming process for the front frame rails and engine crossmember ensures much more accurate dimensional placement of critical mounting brackets and suspension pick-up 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 translate to enhanced quality.

Compare the new frame of a 1999 four-wheel-drive extended cab model to that of its current counterpart, say GM engineers, and you'll discover a 2-in. (5-cm) longer wheelbase, wider front and rear track and significant improvements in torsional and lateral rigidity. GRADE: B

n TRUCK-LIKE APPEARANCE

This is a decide-for-yourself matter - and all we can show for now are GM-released sketches - but we'll stick out a collective neck and say the new trucks' styling will do just fine.

No, neither the Silverado nor the Sierra is as gregarious and potentially trendy as the Ram, or as fine-tuned-aggressive as Ford's F-Series, but long-standing 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 the one to have for those who would have had GM stylists take a few more risks. GRADE: B-

n GREAT DRIVER AND PASSENGER ENVIRONMENT

Well, "great" is a bit subjective, but there's little doubt the increases in cabin volume will be welcomed by today's concert-hall-space- obsessed truck buyers. There's a tidy 2.5 ins. (6.3 cm) more space from the front bumper to the back of the cab, 3.1 ins. (7.8 cm) 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 spank both Chrysler and Ford full-sizers - yet the early press materials indicate the new GM trucks lose 0.4 ins. (1 cm) of front legroom and 1.6 ins. (4 cm) of rear legroom to their predecessors. Hmmm . . . There's an all-new interior, of course, led by a floor height lowered by 1 in. (2.5 cm). The instrument panel is cleaner, with typically clear GM dials and materials that look neither expensive nor cruddy, just durable.

Unfortunately, GM engineers forgot a door. That's right, extended-cab versions of this all-new truck will come with just three doors at a time when both the Ram and the F-Series can now (or soon, in the case of the F-Series) be had with a second door on each side, swinging opposite the front doors.

"There was a lot of debate about that," says one development engineer rather noncommittally. "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 that the feature was deemed essential too late in the development process to be engineered in time for the new trucks' launch. A serious miscue. GRADE: C

n OUTSTANDING POWERTRAIN PERFORMANCE

Ford and Chrysler are in for a pounding here. GM Powertrain engineers have cranked out their own iron-block version of the Corvette's LS1 OHV V-8 - an engine that 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 lineup includes a 5L and two 5.7L variants.

Trouble for the competition comes when it's time to match ponies. The 4.8L makes 255 hp to the Ford 4.6L SOHC V-8's 220 hp. Jump up to the Vortec 5.3L, a displacement where Ford and Chrysler both play, 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.

Want to move up to the really big leagues? The new 6L Vortec has no cause for shame when delivering 300 hp. Ford's tiring 5.8L V-8 is good for just 210 hp and Chrysler's 5.9L makes 245 hp. That's 90 hp over the Ford and 55 hp better than Chrysler. Oh yeah; the base engine remains a 4.3L V-6, but who wants that?

No contest. The new GM V-8s kick butt (at least on paper). GM truck devotees will be ecstatic. GRADE: A

n OUTSTANDING HAULING AND TRAILERING

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

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

n AFFORDABLE TO OWN AND OPERATE

Generously equipped full-sizers are fetching more than $30,000, and the new GM trucks won't miss out on that free-for-all. But because the trucks are still many months from launch, we have no firm idea about price structure.

On the operating-cost side, everyone expects low-maintenance, and GM won't disappoint. There are 100,000-mile (162,000-km) tuneup intervals and the new dual-accessory drive belts are designed to go 150,000 miles (230,000 km). You get the idea. GRADE: INCOMPLETE.

n SAFETY AND SECURITY

GM has finally done the right thing with brakes: 4-wheel discs 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 also prattle about more comfortable seat belts and anti-theft capabilities, but the brakes are the safety story. GRADE: B+

n FUNCTIONAL CARGO AREA

There's a big open box back there. You can put stuff in it. You can tie said stuff down. Dogs enjoy traveling while located in this area. GRADE: PASS

We've graded the 1999 Chevrolet Silverado and GMC Sierra based on static presentation, with no driving experience. The grades are better than competitive and extra points are in order for numerous smart details that will be discussed when a more complete evaluation is permitted.

In the end, though, customers will decide if GM has made the right moves. The company's had 10 years to think about it.