The Chevrolet Tahoe Hybrid, along with its GMC counterpart, the Yukon Hybrid, are the first vehicles to utilize the advanced two-mode hybrid powertrain developed jointly by BMW, DaimlerChrysler, and General Motors. This full-size SUV launches a new breed of larger vehicles that are significantly greener than their gas-powered versions. Maybe that's why the Tahoe Hybrid received the questionable title of “Green Car of the Year” at the 2007 Los Angeles Auto Show. The panelists may have jumped the gun a little, as this hybrid doesn’t even meet the corporate average fuel economy (CAFE) standard.
The crux of the Tahoe Hybrid’s powertrain is GM’s 6-liter Vortec V8 with cylinder deactivation technology. In other words, this engine can shut down four of its eight cylinders when the additional power is not needed. That saves fuel. Beyond the engine, there’s a 300-volt battery that hides below the second-row seats. The vehicle's two electric motors are housed within the transmission.
In order to keep the vehicle running at peak efficiency, this hybrid system is able to run in one of two separate modes—hence the name "two-mode hybrid." For low-speed, low-impact driving, the powertrain works just like other hybrids; it stops the V8 engine whenever possible so that it may draw power from one or both of the electric motors. The second mode is mostly for highway driving, at which time one or both electric motors can run concurrently along with the V8 engine in order to provide a power boost. The two-mode transmission is the key to the whole system, which attempts to keep the engine running at the optimum rpm for low fuel consumption. Essentially, it manages a balancing act between the V8 engine and the electric motors. It is also responsible for making the transitions between the two modes practically seamless
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