Unless you're a GM aficionado, it would be easy to miss the fact that a Hybrid Tahoe is in fact a hybrid, at first glance. No doubt, that's exactly what Chevrolet was planning. Appearance-wise there's really not much difference, aside from the badging and additional hybrid graphics that adorned the press vehicle we tested. The grille is a bit more tapered at the bottom, and the bumper cover is more flush with the grille. C-pillar plastics provide a more streamlined path for air, but are hard to notice. It is practically the same interior that we've grown to love in our Silverado LTZ.
The real difference comes when you first fire up the 6.0L engine. (Yes, the hybrid uses a larger engine than the standard Tahoe, more about that in a minute.) The typical sound of a starter engaging the flexplate is gone, replaced by a muted growl as the engine fires up from the electric motor attached to its crankshaft, where a torque converter would normally be. It's even more noticeable when using the remote start, because from inside the cabin, the engine noise at idle is hardly audible. In fact, throughout the engine's operating range, it seems quieter.
The 2-Mode hybrid system in the Tahoe was a joint engineering project between BMW, Daimler-Chrysler, and GM, and uses packaging dimensions similar to traditional automatic trans-missions. We had GM engineers explain the intricacies of the system in person, with a cut-away 2-mode system to help us out, and it's still complicated, but here's the shortened version.
The planetary gears are still there, but rather than a torque converter, there are two electric engines that can either generate power or propel the vehicle down the road. The difference between engine speed and transmission speed is absorbed here, much like a torque converter, but rather than excess energy heating transmission fluid, it can be used to generate power. This happens while the engine warms up and the vehicle isn't moving.