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Diesel’s Embrace Of Gas-World Components And Strategies

For years, diesel drag racing was static-like. Most Pro Street trucks were stuck in the 9’s, the Pro Mod field was miniscule, and the index classes were hit or miss. The sport wasn’t as fast-moving as it is today. Literally. To be sure, diesel drag racing was exciting to watch and saw moderate growth, but what’s occurred over the past five to seven years has been extraordinary, and a lot of it has had to do with the industry’s embrace of gas-world go-fast parts and racing strategies. Looking across the aisle has given birth to more rear-wheel drive vehicles and tube chassis arrangements on coil overs as opposed to almost everything being based on a 4×4 ¾-ton or larger truck still packing leaf springs and a factory frame.

Beyond that, four-link suspensions, electronics, aftermarket axles and transmission brakes are now everywhere. And speaking of transmissions, the Turbo 400 has had a major impact in the upper tiers of diesel drag racing since it was first embraced. Once a few drivers blazed the TH400 trail and proved it would work, several others followed suit. Now, it’s the transmission of choice in the Pro Mod category, and we’re even seeing four-wheel drive applications in other classes—including on the world’s fastest Pro Street truck. Similar to the way diesel truck pulling has borrowed much of its technology from the tractor world, diesel drag racing has adopted some of the most successful gas world components. As a result, today’s diesel racing scene is downright impressive—and records are often set and then broken again from event-to-event.

Released in the 1960s and the successor to the Powerglide, GM’s Turbo-Hydramatic 400 (also known as the TH400, THM400, or Turbo 400) is one of the strongest factory-offered transmissions ever produced. Once the TH400 was successfully used in diesel drag racing, it was a game-changer for the sport. Although the Powerglide has been tried, the Turbo 400 is better suited for most diesels, almost all of which are heavier than 3,200 pounds and run large tires. The TH400 holds up to the weight of the vehicle better, and thanks to being a three-speed also have the large rpm drop you typically see with a two-speed.
So who’s building the baddest Turbo 400’s in the business? In the diesel world, Sun Coast has had its hands in many high-horsepower builds while Rossler Transmissions—a big name in the gas game—has had an undeniable impact. A Rossler TH400 has been along for the ride on various record-setting passes, as well as championships in Pro Street and Pro Mod. Rossler is also the only TH400 builder to have helped get a diesel into the 3’s in the ‘660—that vehicle being Firepunk Diesel’s Pro Mod S10.
Within a top-of-the-line Rossler Turbo 400, you’ll find a host of upgrades, many of which have been track-tested for decades. In most diesel-spec’d units, a larger, space age alloy material input shaft is used, as is a larger, space age alloy intermediate shaft, along with a 300M output shaft. To save weight while adding strength, a 7075 T6 billet-aluminum forward drum sheds 4.5 pounds and is reinforced with a 4140 billet insert. A billet-aluminum direct drum, a billet and heat-treated second gear pressure plate, a larger direct sprag, billet gear set options, and a boat load of other components help make these things live reliably under immense abuse.
To be sure, built-to-the-hilt Turbo 400’s do break, but so does everything that sees the kind of stress a 3,000hp diesel weighing in at 3,300 to 5,000 pounds imposes on a vehicle. However, what a TH400 doesn’t do is destroy transmission cases (which is the case in many 48RE applications). A lot of this outer shell strength comes from the use of the aftermarket TH400 case manufactured by Reid Racing. Reid’s Super Hydra 400 case is tough yet ductile, and chock-full of improvements such as 360-degree internal case lugs, which retain the center support and pressure plate.
The secret sauce for any diesel-rated transmission lies in the torque converter. Over the past five to seven years, one giant gas world name has become more and more involved in building lock-up converters for diesel racing applications. That company is Neal Chance Racing Converters. Its latest, 12-inch, all billet-aluminum bolt-together lockup unit was in use during the quickest eighth-mile pass in diesel history—the 3.99 put up by Firepunk Diesel in February, 2021.
Another converter that’s seen great success is Sun Coast’s Pro-Loc billet lockup converter. Its bolt-together converter is machined from a solid piece of 7075 T6 billet-aluminum plate (eliminating ballooning), and incorporates the company’s patent-pending Zero Drag lockup technology. That fancy language means the clutch surfaces see constant oil flow to quell heat and improve service life, there is less parasitic loss (more power to the ground), quicker throttle response for the race vehicle, and faster spooling of big turbochargers. Sun Coast’s modular clutch basket allows for plenty of tunability, with the ability to run up to five double-sided Zero Drag clutches.
You can find Sun Coast’s Pro-Loc billet lockup converter in action each time Stainless Diesel’s common-rail Cummins-powered second-gen blazes down the track. Built by Wilson Patterson Diesel with a Reid Racing case and also employing four-wheel drive, the TH400 under this Dodge has contributed to a 4.82-second pass at 156 mph—the current world record for a Pro Street diesel truck. Fine-tuning of the converter was performed by changing the stator out and altering the clutch count. At the present time, the converter is fitted with five double-sided Zero Drag clutches.
According to Stainless Diesel’s Johnny Gilbert, “We have never hurt a clutch pack on this TH400. We usually break the sprags in the transmission, but everybody with a 400 fights that a little bit.” As opposed to many factory-based diesel transmissions, a common point of failure with the TH400 boils down to a $14 Low Roller sprag from BorgWarner, with the second gear sprag breaking shortly after that occurs. Beyond that, things get more expensive, but the costs still pale in comparison to what Johnny and his team used to fight with the previous 48RE(s): cracked transmission cases..
Precision Performance Products’ PowerShift air shifter is a common sight in high-end diesels these days, and for good reason. It allows for hands-off shifting and offers smooth, precise operation as well as a slim design. It also comes with the air cylinder, CO2 tank and everything else required to run it. We’ve even seen this particular air shifter activated via nitrous in at least one application, too.
Due to their inherent heft, you don’t see a lot of Dana 80 or AAM 1150 rear axles in the top tiers of diesel drag racing anymore. Instead, you’ll find an axle that’s long been embraced by the gasoline world due to its durability: the Ford 9-inch. Though it debuted in the 1950s, it lingers on to this day thanks to its strength—namely from its larger offset between the ring gear and the pinion gear centerlines, and its extra pilot bearing support for the rear of the pinion. As a bonus, the aftermarket has had its hands in the 9-inch for more than six decades, so its’ beyond proven at this point.
The 9-inch version shown here comes from Strange Engineering. Its fabricated differential housing features a wide-web design for increased rigidity, but also features internal gusseting for tremendous strengthening. Instead of bulletproofing a factory AAM 1150 or Dana 80 and having a heavy piece of hardware, a 9-inch that’s done up in this manner saves weight while being extremely rigid. Though it wouldn’t survive the rigors of truck pulling, a well-built 9-inch fits the bill perfectly in diesel drag racing.
In some applications, you can even find a 9-inch both up front and out back. Such was the case on Lavon Miller’s and now Josh Scrugg’s ’06 Dodge (the infamous four-wheel drive Pro Street truck that was the first to break into the 7’s in the quarter-mile and dip into the 4’s in the eighth-mile).
Not that two wheel drive vehicles were exclusive to the gasoline world, but up until a handful of years ago there weren’t a lot of them competing outside of the dragster and Pro Mod categories at diesel events—and if there were, they weren’t much (if any) faster than the four-wheel drives. Much of that changed when a few pioneers shed some light on the benefits of running a lighter weight, rear-wheel drive application with a proven chassis setup. To be clear, 4×4 still dominates in diesel drag racing, but a nice mix of RWD vehicles has made things very interesting.
One rear-wheel drive truck that had a huge impact on modern diesel drag racing was Dustin Jackson’s ’94 F-150 Lightning. Running on common-rail Cummins power, packing a Rossler Turbo 400, and utilizing a 9-inch out back, his lightweight Ford dominated the Pro Street category for two full seasons. In addition to the driver side tire often leaving the ground, Jackson typically cut 1.3-second 60-foots in the “Old Hustle, New Flow” Ford, and he could run 5.0’s in the eighth like clockwork.
With one quick look at the Outlaw Diesel Super Series’ 5.90 Index class, there are several rear-wheel drive contenders. One of them is 2020 champion, Rod MacMaster, with his short-bed ’07 Dodge 2500. At 5,800 pounds, his ride is rumored to be the heaviest truck in diesel motorsports campaigning a Turbo 400 transmission. The big shaft TH400 came from Sun Coast, as did one of the company’s Pro-Loc billet lockup converters.
Another lights-out 5.90 Index truck comes in the form of David Large’s stunning third-gen half-ton Ram. His rear-wheel drive Dodge makes use of a Rossler TH400 with Sun Coast’s Pro-Loc billet lockup converter and is one of the most consistent trucks in its class. As we went to press, David was very much in the hunt for the 2021 title in 5.90. In this photo, he faces off against the aforementioned Rod Macmaster.
Back-halving and tube chassis’ are more common now than ever before in diesel drag racing, and leaf springs have all but disappeared in the fastest classes. This is where coil over shocks have been big, and a lot of the gas-world technology has been carried over to diesels. One look under a 5.90 or quicker diesel these days and you’re bound to find hardware from either Menscer Motorsports, QA1, AFCO, or Chris Alston’s Chassisworks.
A wheels-up, fourth-generation Mustang has gasser written all over it, right? Not this one! When Daniel Pierce brought this Cummins-equipped pony car to the 2018 Scheid Diesel Extravaganza it was one rowdy ride. It sported a square tube chassis, a 9-inch rear end, Menscer Motorsport D.A. coil over shocks and struts, and boasted a race weight of just 3,300 pounds. Daniel has since sold the car, but tremendous potential exists in a setup like this.
The age-old, set-back engine trick has always been a means of obtaining better weight distribution. Thanks to being fitted with engines that usually tip the scales at more than 1,000 pounds fully dressed and turbo’d, diesels arguably need improved weight biasing more than any other vehicle in drag racing. Stainless Diesel’s deck-plate 6.7L Cummins (shown here) is set back considerably in its Pro Street Dodge.
The ability to fine-tune the engine and log virtually any kind of data imaginable helped pave the way for electronics to rule the day in diesel drag racing. As diesel enthusiasts began to embrace electronically controlled engines (i.e. common-rail), drag racing became more consistent, with repeat performances becoming much more frequent. The diesel race teams of 2021 take notes and go over every log meticulously. Ground speed, shock travel, G-force, yaw degrees, engine data, shift points and anything else you can think of is being analyzed between passes to both help improve in the next race or find out what went wrong during the previous one.
Just as the ability to integrate multiple controls into a single system has advanced the fuel injected gas world in leaps and bounds in recent years, it’s done the same for diesel. Calibrators and racers can now control injection timing, boost, and even traction with one operating system, not to mention make use of various 0 to 5-volt system inputs, accommodate wheel speed, turbo speed, crankshaft, and camshaft sensors, and also utilize power output functionality. This ability to fine-tune based on collected data leads to consistency out on the track and is a big reason why we now have 2,500 to 3,000hp diesels surviving round after round during eliminations.
Speaking of fine-tuning, many diesel drag racers rely on the Bosch Motorsport MS 15.1 stand-alone ECU to dial everything in. In today’s high-horsepower diesels, four-wheel drive or two-wheel drive, most would be dumbfounded by how many times fuel is pulled out of the equation and then poured back in within the first 60-feet. Fine tunability of a common-rail’s injection system is directly linked to traction, and traction is what ultimately wins the race.
Not that it was directly stolen from the gas world, but four-link suspension systems are everywhere in diesel drag racing these days. In most cases, four-wheel drive applications sport front and rear four-link arrangements for ultimate bite at the track. Although a four-link system has its share of limitations, once the right pinion angle is established (along with sound wheelie control and the right amount of ballast, if applicable) and the chassis is happy on the launch, its cost to effectiveness ratio is hard to beat.
Even the Turbo 400’s successor, the 4L80E, has been successfully campaigned in diesel drag racing, and one of the best examples can be found in Buddy Callaway’s ’03 GMC Sierra 2500. Thanks to his Twisted Diesel-built and PCS 2800-controlled four-speed, Buddy’s 5.90 Index truck is a regular late-round performer on the ODSS circuit, and his quick-shifting setup has also earned him the honor of owning the fastest stock long-block LB7 Duramax through the eighth-mile in the world. Rick Fletes’ rock-steady Duramax Chevelle also uses a 4L80E (built by Casner Racing Enterprises) with a PCS 2800 controller.
The days of getting by with a full factory frame and even leaf springs have long slipped away in diesel drag racing, as full tube chassis builds and back-halfs are now the norm in the upper tiers of the sport. This includes tubbing and narrowed rear-ends—and it’s not about looks. Diesels are now in need of these things thanks to so much power being on tap. Big name company’s such as Greg Risk Racecraft, Jerry Bickel, and Tommy Mauney have even been summoned for chassis builds, proven components, and advice. One thing is for sure, the more that hardcore diesel racers intermingle with the great minds of the gas world, the more diesel drag racing will continue to advance.

SOURCES

Bosch Motorsport
bosch-motorspor.com

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Menscer Motorsports
910.491.2798
menscermotorsports.com

Motec
motec.com.au

Neal Chance Racing Converters
316.542.9869

racingconverters.com

Reid Racing

925.935.3025

reidracing.biz

Rossler Transmissions
330.530.5000
rosslertrans.com

Sun Coast
850.695.9679
suncoastdiesel.com

 

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