One of the hottest new trends in drivetrain technology – which really isn’t new but is more of a resurgence of sorts – has been the design and use of what’s known as a lockup torque converter. A lockup converter, as the name implies, seeks to eliminate the slippage of a standard torque converter that robs horsepower by locking the forces of the flywheel to the output shaft. This creates a 1:1 mating, similar to when a clutch locks up and goes 1:1. This technology in drag racing dates back to the 1970’s and has been dabbled with in the years since, but only now are manufacturers really beginning to place an emphasis on the technology.

One of those manufacturers, Hughes Performance, launched their new XP5 lockup transmission/converter system a couple of years ago. Hughes utilized an original Powerglide transmission design, but the package measures roughly one inch longer, thanks to the addition of a unique new input, a different front pump, a different valve body, and all of the lockup circuitry. Available in 9 or 10-inch models, the XP5 is operated via a 12V solenoid or a timer on the transmission valve body that uses line pressure to lock up the clutches inside the converter. The driver can actually activate the solenoid with a button or switch mounted in the cockpit.

Keeter Performance Engineering utilizes one of Hughes’ XP5 systems in their 2,500+ horsepower, supercharged, 582 cubic inch Top Dragster driven be Lee Lightfoot, and they’ve captured several videos that accurately illustrate – audibly – how the lockup converter works in practice.

As you watch the video shown above, you’ll hear the 1-2 gear change just prior to the 300-foot marker as normal, but at around 700-feet, the XP5 system goes 1:1, creating what sounds like an additional gear shift. What you’re hearing is in fact not a shift, but the engine RPM being dragged down as the drivetrain goes 1:1. At this point, virtually every drop of that 2,500 horsepower is being transferred to the rear end housing and to the tires. As you can imagine, this provides some advantages in the speed department, and users of lockup converters have consistently seen gains in the quarter mile trap speed. Big gains in some cases.

Oh, for those curious, Lightfoot clocked a 6.25 at 225 mph on this run.

For more information on Hughes Performance and their XP5 lockup system, log on to hughesperformance.com.