It's unclear what the three-row vehicle will be named when it goes on sale, tentatively scheduled for the second half of 2017, the sources said. A GM spokesman declined to comment.
The new vehicle could give Chevy more flexibility to answer rivals that use a mix of crossovers and SUVs to cover some market territory where Chevy is absent. The Ford Edge and Nissan Murano are slightly larger and more upscale than the Equinox, for example. The Honda Pilot, Toyota Highlander and Nissan Pathfinder offer three rows of seating, but in a smaller footprint and with better fuel economy than the Traverse.
With the new entry, Chevy would have three crossovers that roughly line up sizewise against the potent Escape-Edge-Explorer trio from Ford.
The strategy extends beyond Chevrolet, though. The shorter wheelbase also will underpin the successor to the Cadillac SRX, called XT5, when it arrives by next spring. And it will serve as the bones for the next-gen GMC Acadia, which will shrink to a three-row midsize when it is launched in mid-2016, the sources said.