2002 Chevrolet Corvette - The Million Dollar Vette

An eight-speed C5 that coulda, woulda, shoulda been

From the August, 2011 issue of Vette

By Steve Temple

Photography by Steve Temple

Imagine if you could significantly improve both the acceleration and fuel efficiency of your Corvette without even touching the engine. In theory, the approach is fairly simple: Divvy up the powerband with a close-ratio, semi-automatic, eight-speed gearset. This would give the car much more torque and horsepower through the gears, since the engine would drop only half the rpm on each shiftùand there'd still be a top gear with overdrive for low-rpm, long-range cruising.

In practice, however, the realities of corporate politics ended up stifling this significant performance modification for the C5. Even so, it serves as an intriguing behind-the-scenes story of a technological groundbreaker, one that dramatically demonstrates what can be done to optimize the power delivery of not only Corvettes, but of restomods and muscle cars as well.

To set the stage for this insider account, look back to the era of the C4 Callaway Vettes. Those twin-turbo models had way too much power for the factory drivetrain to handle, so Hydramatic supplied a stouter Turbo-400 trans with a Gear Vendors overdrive.

For those not familiar with Gear Vendors, this company is well known in the muscle-car ranks for enhancing those vehicles' crude-but-stout transmissions with bolt-on overdrive systems.

Truck and RV enthusiasts use gear splitters as well, but mostly for lowering revs at cruising speed for better fuel economy and reduced engine wear. (For instance, one of this author's personal vehicles is a one-ton diesel dualie, and it runs down the highway at 70 mph while turning only 1,800 rpm!)

Getting back to Corvettes, while Gear Vendors makes aftermarket upgrades for earlier models, in 2002 company president Rick Johnson and Jon Moss (GM's special projects manager at the time) hatched an idea to apply this versatile technology to a C5. Not one to miss a potential business opportunity, Johnson figured this project car might lead to a long-term contract for an OEM option using Gear Vendors products.

Looking to debut the car at the SEMA show, which was only a few months down the road, he prevailed upon Bob Kern of GM to supply Gear Vendors with a new C5. Kern obliged, also providing extra torque tubes and transmission assemblies for mockup and engineering work.

Gear Vendors received an Electron Blue automatic coupe and began making the components. The car's drivetrain layout meant that the overdrive would need to be located directly behind the engine, a significant departure from the company's typical bolt-on transmission arrangement. As a result, there were a number of parts to design and fab.

It took about 30 Gear Vendors employees working feverishly to engineer, test, and install the new systems in the Corvette over the next five months. They came through in the nick of time, finishing by the October 31 deadline, and Johnson delivered the car to the Las Vegas convention center so Moss and GM Performance's Mark McPhail could do some hands-on testing. Both were elated with the car, comparing it to driving an F1 car in a videogame: "Just too much fun!" was the expression they used.

Why so? Comparing the stock and Gear Vendors drivetrain configurations is telling. When in factory form, the C5's 4L60E four-speed has only two underdrive ratios, plus a Third-gear direct drive and a Fourth-gear overdrive. With the gear splitter, it now had four close ratios of underdrive, a direct drive, and two overdrive gears.

In addition, all those extra gears were available at the push of a MasterShift paddle shifter mounted on the steering wheel. This trick setup uses Gear Vendors programming information to make a truly versatile dual-paddle, two-button system. With the paddles you can pull the right side for close-ratio upshifts through eight speeds and down through the same on the left. The button on the front of the paddle allows for stock four-speed wide ratio changes as well as a stock Drive mode. Virtually any car with a Gear Vendors unit can make use of the system.

As noted at the outset, translating all these extra choices into the driving experience means the car has much more power on demand as you work your way through the gears, since the engine drops only half as many revs on shifts. So rather than experiencing a precipitous "gear gap" between each shift (anywhere from 30 to 47 percent), with the Gear Vendors unit it's largely between 10 and 22 percent.