NEW YORK (FORTUNE) - Although it has been around for more than 100 years, GMC is the auto industry's forgotten brand. Even its history is shrouded in mystery.

Urban myth has it that its initials stand for Grabowski Motor Corp., after its founder, Max Grabowski, who started the truckmaker in 1902 and sold it to GM (Research) in 1912. In fact, Grabowski called his company"Rapid Motor Vehicle," and the GMC name didn't appear until after GM took over.

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A rarity in the auto business, GMC sells no passenger cars - only pickups, vans, and SUVs - making it one of only three all-truck brands (Jeep and Hummer are the other two). Still, GMC is GM's second largest brand after Chevrolet. Last year, it sold 537,772 trucks and ranked as the eighth largest brand in the industry.

That's despite having one of the least distinct product lines and poorest defined images around. Every vehicle in GMC's lineup is shared with Chevrolet, which sells them at higher volume. But GMC will take a big step forward at the end of this year when it introduces the Acadia, a seven-passenger SUV crossover based on GM's Lamda platform, which it will share only with Buick and Saturn

Recently, Craig Bierley, GMC's product director, came to New York City to talk about Acadia and other GMC plans.

"We've had sales records in 11 of the past 13 years. Southern California, specifically Los Angeles, is our strongest market. Our share level there is greater than the national average, which is somewhat of an anomaly for a domestic automaker.

"Last year was not a record. We saw a deterioration in mid-size and full-size utilities. Some of it was related to gas prices and some of it was attrition due to the fact that we had a new model coming.

"Our strategy on fuel economy is improving existing technologies in our gasoline engines with active fuel management, and variable valve timing. We also led in E85 capable vehicles. This year GM is going to build 400,000 of them. The ethanol infrastructure needs to catch up with what we've done.

"Another piece of that with long- term potential is certainly hybrids. With Yukon for example, we've got a hybrid coming in 18 months - a two-mode, full-hybrid system that provides s a pretty significant improvement in fuel economy.

"One of the ways we've chosen to differentiate ourselves from Chevrolet - and it has been very successful for us - has been the Denali. We introduced it as trim level on the Yukon SUV in 1999. It is now nearly 40 percent of our Yukon business. We've got a Sierra Denali pickup, which, although it is a small volume play, we've seen an increase since we moved from an extended cab to a crew cab. The Envoy Denali is well over 30 percent of our Envoy SUV sales.

"These are things that allow us to differentiate our brand vs. Chevrolet. The first time we really made a conscious effort to do this was with the Envoy and the Chevy TrailBlazer a couple of years ago. If you look at the old Blazer and what we used to call the Jimmy, it attracted the same customer and sold for the same transaction price. When we made them different, we made them both better and they both attracted a more desirable demographic. But GMC widened the gap. We attracted a different buyer and sold for a higher price.

"That experience solidified the notion of making GMC and Chevrolet as differentiated as possible with product characteristics, styling, and design. It is common sense, I know, but our experience taught us there really is something here and that GMC is not just Chevrolet's little brother. In the products that we have coming, we tried to increase the differentiation. The Lamda SUV is unique from the standpoint that Chevrolet doesn't have it. I think that is the first time that has ever happened.

"There is clearly a move, especially in the mid-utility space, to more BFI - body frame integral - crossover SUVs. We also call them car-based SUVs. So it is absolutely critical to us to have an entry to play in that segment. We still see, even in our long-term projections, truck-based and car-based SUVs coexisting.

"The whole idea behind GMC is really about engineering and that our trucks have capabilities that exceed the customer's requirements. We think that tent is big enough to not just be brute force kind of trucks, but that there is an opportunity to take a product like Acadia, with its great on-road characteristics, and say that, it too, is a well-engineered truck that offers capabilities that may exceed your requirements and fits within the GMC professional grade ethos. "