General Motors may derive rear-drive Buicks and Pontiacs from an exclusive Cadillac vehicle architecture. But don't expect any Chevrolets based on Cadillac underpinnings.
A less costly version of Cadillac's Sigma vehicle architecture is a candidate for several rwd cars now that GM has killed plans for its rwd Zeta architecture in North America.
"A natural place to land would be Sigma," Jim Taylor, Cadillac general marketing manager, said last month at the New York auto show.
Taylor said another option is re-engineering Holden's VT architecture, which is the basis for the Holden Monaro and Commodore and Pontiac GTO.
Financial difficulties
GM's financial difficulties were blamed for the Zeta decision announced last month. The architecture was being developed for a variety of rwd Buick, Pontiac and Chevrolet cars that would begin to debut in 2007. All-wheel-drive versions also were planned.
The GM product plan would have emulated the Chrysler group's strategy by replacing its front-drive, mid-sized high-volume car lineup of rwd models.
"I don't think I would conclude that plans for rear-wheel vehicles at GM are cancelled forever," GM Vice Chairman Robert Lutz said last month at the New York auto show. "I see it more as a delay. We will study other ways to get at rear-wheel-drive passenger cars."
Still in the product plan
Taylor said some rwd cars originally based on the Zeta architecture remain in the product plan.
He said a possible architecture for some of these models is a less costly version of the Sigma vehicle architecture, referred to internally as "Sigma-lite."
The Sigma architecture is used exclusively for the rwd Cadillac CTS, STS and SRX.
Before taking his current position at Cadillac in August 2004, Taylor was vehicle line executive for Sigma. The first Cadillac to use the architecture was the 2003 CTS.
When the Sigma architecture was being developed, Taylor said his team investigated whether it was possible to use cheaper components to create vehicles for brands below Cadillac.
"It was a quick study on the component side to see whether we could create Sigma-lite, and it was feasible to do," he said.
Range of vehicles
GM later decided to do a range of rwd cars for Chevrolet, Buick and Pontiac. But the Sigma-lite architecture proved too expensive for models that might be priced below $25,000.
The automaker decided to develop the less costly Zeta architecture, which could be used on a global basis and applied everywhere from Chevrolet to Cadillac. But on March 21, Lutz announced that GM had canceled plans for using Zeta in North America.
According to supplier sources, Zeta was going to be used for the next-generation Chevrolet Impala and Monte Carlo; Pontiac Grand Prix and GTO; and two Buick models - a coupe or convertible based on the Velite concept and a sedan. The Chevrolet Camaro name also was going to be resurrected for a four-passenger coupe.
Zeta was one of two vehicle architectures under consideration for an ultraluxury sedan planned by Cadillac that is expected to debut at the end of the decade.
maybe one day. 
