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GM's full-size SUVs may switch to unibody construction

The first Chevrolet Suburban was built all the way back in 1935, making the model one of the longest continuously running nameplates in automotive history. For all of those 73 years the Suburban (and later its smaller Yukon and Tahoe brethren) has been built on underpinnings from the automaker's pickup trucks, but it now looks like the long-running marriage between pickups and full-size SUVs may be about to end -- the General is considering switching the vehicles to lighter, unibody construction.

Though its current crop of large SUVs was unveiled in just 2006, continuously rising gas prices have steadily eaten away at demand. Until recently the automaker decided to cut production by 50,000 vehicles this year. In addition the new, stricter CAFE standards will penalize truck-based SUVs because of their short wheelbases and poor fuel economy. Because of this, GM's engineers have secretly contemplated basing their next-generation Suburban, Tahoe, Yukon, and Escalade on a lighter, unibody design. No official decision has been made, but the shift could come as soon as 2012.

Unibody construction would help improve two of the most glaring weaknesses in the current crop of GMT900 trucks -- cramped interior space and bad gas mileage -- but at the expense of off-road ability and towing capacity, which are some of the main reasons consumers opt for the hulking machines. In addition, developing Tahoe and Silverado underpinnings separately would reduce profit margins, and given that the large SUV's are some of GM's most lucrative vehicles, the automaker may resist making the switch.

If the General did decide to build unibody Yukons and Escalades, another issue that could arise is what to do with the automaker's current crop of three-row crossovers. The GMC Acadia, Saturn Outlook, and Buick Enclave are selling well, and a fourth variant, the Chevrolet Traverse, will soon be joining the stable. Moving the GMT900 vehicles away from body-on-frame construction could cannibalize the new crossovers' sales, which GM definitely would want to avoid, but then again if demand for truck-based SUVs continues to plummet, the company may have no choice.

Like many automakers, because of rising gas prices and upcoming CAFE standards, GM is moving toward lighter vehicles and smaller-displacement engines, and ending the body-on-frame SUV era would seem like a logical next step. Then again it's also possible that the General's two-mode hybrid system and other powertrain advancements could help save the full-size vehicles, at least for the near term. But whatever happens, don't expect the automaker to retire its famed Suburban nameplate anytime soon.