The Beauty Of Gear SplittingThe first thing most people think about when contemplating the purchase of a Gear Vendors overdrive is the improved fuel economy. The thought coming just after that is imagining what it would be like to extend the life of a high-performance engine by another 25 percent before needing an expensive rebuild. If the credit card isn't out by then, you're a really tough customer, and you may also need to ponder the improved quality of the driving experience that allows you to, say, hold a non-screaming conversation with a passenger, or listen to the radio at a reasonable volume level. We would also like to offer you another reason: gear splitting.
In a drag racing scenario, it is the average power applied over time-rather than fuel economy-that trumps all else. In a perfect world, the drag racer would keep his engine at peak power continuously for the entire run to maximize his e.t. But that can't happen, partly because the transmissions in use behind high-powered engines tend to be simple, beefy two-speed Powerglides, or three-speed Turbo 400s. These transmissions can take loads of abuse, but their limited number of gears necessarily forces the engine out of its optimal operating range at some point.
Enter the Gear Vendors overdrive. For our purposes here, we can take the overdrive concept and turn it on its head. Whatever numerical rearend gear ratio that was optimal (without overdrive) for peak power going through the top end can now be multiplied by a factor of 1.28 for even more grunt off the line. (If you were using a 3.73 gear, a 4.88 gear will now give you close to the same finish-line rpm.) At the point where you run out of gear without the overdrive, kick it into overdrive for the dash to the finish line right in the meat of your power curve. The end result is that your engine stays near its peak longer-and quicker e.t.'s and faster trap speeds are the outcome (you may even find yourself needing only a nominally shorter gear as a result).
But the advantage doesn't end with just having an overdrive. Try splitting the gears between one-two (and two-three if you have a three-speed like a Turbo 400 or Ford C4). You'll stay near peak power for even longer, for improved e.t. Don't believe us? We found Jim Luttrell, a veteran Super Comp racer from Apache Junction, Arizona, using a Gear Vendors overdrive in just such a fashion-with race-winning results. We spoke with Jim about his experience racing a dragster at over 200 mph with a Gear Vendors overdrive, and here's what he had to say:
"I run a Powerglide, and we've worked to split the gears with our Super Comp dragster. For a while, I was just using it as an overdrive to bring the rpm down-to bring it back into the torque curve-at the top of the track. Then we moved to NHRA Super Eliminator in NHRA Division 7, and with the Gear Vendors, we were the only Dragster in the division running over 200 mph on a 7.90-second index-right at 204 mph. With the gear splitting, you take off in First gear, then at a set rpm, the Gear Vendors goes into First-over, with the Gear Vendors engaged. When the transmission shifts into Second-which is High gear in a Powerglide-the Gear Vendors will switch back out. Then later on down the track, the Gear Vendors comes back in to keep the rpm down in the engine's torque peak. It basically makes a two-speed Powerglide into a four-speed.