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Sonnax Offers Inside Look at Game-Changing TH400 Smart-Tech Drum Module

Winning a race often comes down to just fractions of a second. The new Sonnax Smart-Tech Drum Module for Turbo 400 transmissions could be a gamechanger for racers looking for those key, incremental improvements in on-track performance, and it offers many other valuable benefits as well.

Traditionally, the Turbo 400 internals are comprised of separate iron forward and direct drums, with lightweight aluminum options available for racing applications. Companies like Sonnax have manufactured these and other internal components to be stronger and more capable, but the inherent design of the 400 transmission does leave the door open for transmission failure, some of which can be catastrophic. Sonnax’s new Smart-Tech Turbo 400 Drum Module is capable of eliminating that situation altogether by replacing the entire OE drum system with a unique combination of lighter and stronger components.

The Drum Module

The concept of a redesigned system was first put into use decades ago by noted transmission guru John Kilgore, who has been credited with a number of innovations over the years. Kilgore sought to make his Superlight Turbo 400 a viable option for Stock Eliminator racers. His design and use of smaller clutches accomplished many of the same goals. Angling the design towards those particular classes perhaps limited the ultimate capability of the concept, as did the manufacturing processes and materials of the time.

Fast-forward to today and Sonnax tackled the original problem with advanced engineering and modern manufacturing. The end result—the Smart-Tech Drum Module—is a monumental step forward in both performance and safety for all levels of competitive racing.

The Sonnax Smart-Tech Drum Module for Turbo 400 transmissions offers a multitude of benefits, including improved performance, efficiency, and safety.

The Smart-Tech Drum Module replaces the factory style, two-drum design with a single drum module that houses counter-rotating components that are 3.3 lbs. lighter than an aluminum two-drum design. With that reduction in weight, it is 53 percent more efficient than an aluminum drum duo, and 68 percent more than an iron drum combination because the mass is more centered in the rotating assembly.

“We intended it to be a system to bring more efficiency to the transmission for class racers,” explains Sonnax High Performance Product Line Manager Gregg Nader. “As it developed, we realized it would have a lot of capacity, too.”

Nader notes that the Sonnax Smart-Tech Turbo 400 Drum Module is capable of supporting anything from 500-3,500 hp.

“That’s amazing unto itself, and then you have the whole safety side. Things can go badly when the drums explode. Within the Turbo 400 transmission the forward drum never explodes or over-speeds because it’s connected to the engine. The direct drum is connected to the geartrain that can hyper overdrive direct drums. With our system, there is no separate direct drum connected to the geartrain to overspeed or explode.”

Beyond that significant change in design, the Smart-Tech Drum Module also features components made from high-strength materials where they are needed and lightweight parts everywhere else.

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Real-World Testing

The development of the Sonnax Smart-Tech drum module quietly operated under the radar for nearly two years in a true skunkworks way as Nader and his engineering team worked with several transmission builders and racers, including John “Hutch” Hutchison, Alan Pope and No Prep Kings racer Scott Taylor, Mike Graham of Virginia Speed Race Cars, and drag-and-drive racers Steve and Dustin Trance to put the Smart-Tech Drum Module to the test in real-world situations.

“Gregg came down and we went over the project,” recalls Alan Pope of Alan Pope Performance Products. “Scott Taylor’s No Prep Kings car has a 4,000-horsepower Hemi and is pretty much a torture test for this thing,” Pope explains. “We went three rounds in the first race with it with no issues in a brand-new car. After a few test runs, we saw two-hundredths improvement. We’ve run the transmission for over a year now. If it picks up 1-2 hundredths, that’s a big gamechanger for your program.”

Pope follows that with, “This module is unconventional and represents great out-of-the-box thinking. In my opinion, they hit a home run with it. It’s innovative, it’s high quality, and the thing most attractive for me as a builder is that it includes everything necessary from the center support to the front pump. At some point, everyone’s going to need one to compete.”

Here you can see the original two-drum (froward and direct) design on the left and the new Sonnax drum module on the right. The difference in cast-iron versus aluminum construction is easily noted, and it’s important to consider that the heavier internal parts are now more closely located at the centerline of the transmission. This requires less power to drive the components.

Another noteworthy contributor to the module’s testing is Mike Graham of Virginia Speed Race Cars, who also builds racing transmissions and runs an early prototype in his Roots-blown Pro Mod.

“Our car is a proven piece and makes for a good test bed,” Graham explains. “It runs 3.70s and we ran the module all last year.”

Graham continues, saying “I was already familiar with the concept. John’s (Kilgore) version was very light duty. This was taking that idea and making it happen with today’s technology and CNC manufacturing. Add in how fast today’s cars are and it was time to make it.”

Once Graham put it to use, he had even more positive things to say.

“We have good data comparing the dual-drums to this design. There is an improvement in the time it takes to shift, and it improves reaction time off the line. I also found that you can run lower line pressure and achieve the same clutch life. You can back up on friction mass as well because it’s so much more efficient. You can run fewer frictions in the intermediate clutch pack and it curbs direct clutch centrifugal apply. I’ve made changes to the delay box because of the reaction time improvement. We put 75-80 runs on the prototype and it looked perfect,” Graham says of his frequent inspections of the unit.

Graham has since sold ten Smart-Tech Drum Modules with two of them fitted behind screw-blown Hemis that compete in an Outlaw Pro Mod series and clock ETs in the high 3.60s at 2,600 lbs.

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“The safety part is a no brainer,” Graham comments. “Later-designed billet aluminum drums don’t fail as often, but still have the potential. This product absolutely eliminates the possibility. It uses a common drum that spins at engine rpm all the time. The sprag shaft is at the centerline of the transmission and doesn’t have the mass to cause a failure. It’s much, much, much safer. The biggest thing is getting people to understand how it operates. Some people tend to believe that it’s only for big-horsepower cars. Other than a street application, this product will greatly enhance the performance.”

3. One of the key benefits of the drum module design is that it eliminates the possibility of a catastrophic failure of the direct drum. Here you can see the damage caused by such a failure, and given that the case is blown apart, the race car, and perhaps its occupant, are at risk of suffering damage as well.

Dave Klaput of Proformance Racing Transmissions was one of the early adopters of the Smart-Tech Drum Module.

“The product is amazing – I think they killed it,” says Klaput. “With this module, we eliminate the anti-rotation because the forward drum and direct drum are one unit—that’s a huge deal. It’s a very well thought out piece. We can run less pressure, which means less power loss. For anybody to buy it and put it together and not have to struggle, the ease of how everything goes together is pretty impressive.”

Sonnax also worked with drag-and-drive racers Steve and Dustin Trance to see how the module would fair behind a high-horsepower street car that also logged hundreds of miles on the street between track runs.

“We put 50 hits on a prototype and are now running a production version,” says Steve Trance. His son, Dustin, pilots their turbocharged 1,200-horsepower 2005 Mustang that clocks low 8-second elapsed times, and they recently finished the 2023 Sick Week event, which included five days of drag racing and over 800 miles of street driving.

“The car would hop and/or spin on the 1-2 shift, but when we put the module in, that stopped because it doesn’t have the inertia to do that. If you have to peddle the car, we don’t have to worry about the drums coming apart,” he explains. “We went from steel drums to the module and our datalogs on an iron drum show a lot of time between shifts. This cuts the shift time in half. For an index or bracket racer, it’s a good move.

“In early October of 2021, we ran it at 352 Shootout and right off the bat, we had to take boost out of the car to slow it back to 8.50. It was about a tenth faster with the module.”

It’s not often we get a chance to hear about the behind-the-scenes testing and development of a new product, but Sonnax has offered this information to us, and by all accounts, the Turbo 400 Smart-Tech Drum Module is a winner. If you think you’d like to put it to the test in your own racing program or transmission business, contact your builder or performance parts supplier. Sonnax has them in production and ready to ship.


Sonnax Transmission Company

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(802) 463-0320


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