Volume II, Issue 7, Page 36

The Fleetwing Transmission

Field test: 6L90 6-speed automatic

In the March issue, we ran a story about the new GM 6L80/6L90 automatic transmissions (and their derivatives) that will become mainstay during the next two years. The purpose of this new line of front-wheel, all-wheel, and rear-wheel drive-oriented transmissions is better fuel economy, fewer operating emissions, and best of all, upping the fun-to-drive factor. We outlined the potential pitfalls of trying to swap one of these cuties behind your LS-powered whatever today. Right now, it’s a lot more complicated to bolt Part A to Part B. There’s the matter of chassis sensors, et al, that are an inescapable part of the “problem.” Inevitably, the aftermarket or GM Performance Parts will come to the rescue.

Failing to score an actual car for this exhibit, we trapped a big red ’07 Silverado 4WD 2500HD out in the swamp. Even sweating like a wild pig, its equipment remained vital: 6.0L engine stuck to a heavy-duty 6L90 6-speed automatic transmission.

So how does this work in everyday life? There are no paddle shifters on the 2500’s steering wheel. Things are a little more mundane here. The 2500 has an ordinary shift lever attached to the steering column. The fat end of the shift lever has a button marked with a “+” and a “-. “  If you want to play the manual part, you move the lever from “D” to “M” and begin the ballet, pressing plus or minus until the whole thing becomes obsessive. The transmission remains in gear until you press the + button to upshift, and vice-versa. Regardless at what gear the manually-selected transmission is in when you come to rest, the program dutifully defaults to Low gear. Setting the selector on full automatic is as easy as nudging the lever up an inch.

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