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At the 2025 Ultimate Callout Challenge, few trucks embodied the old-school diesel drag racing spirit like Karl Mireiter’s 24-valve Cummins. Mireiter, owner of RedLine Transmissions, has been racing diesels since the earliest DHRA days and has built transmissions for customers across the country for nearly two decades. But this particular truck is personal – it’s a recreation of the first diesel he ever raced – built with the same fenders, doors and bed from his original 2001 that carried him to DHRA championships in 2002 and again in 2007.
“I’ve always been a drag racer. Ever since I had a driver’s license, I just fell in love with the hobby,” Mireiter told us. “In 2002, I had a brand new 2001 diesel and I’m like, ‘It’d be cool to race this thing.’ This was before you could buy parts in a magazine. I competed in the first year of DHRA and I won the championship.”
Two decades later, that passion is still what fuels RedLine Transmissions and the trucks Karl builds for himself.
Building a Clean Slate
To rebuild his race truck, Karl sourced a donor chassis out of Arkansas. It looked promising at first – until teardown began.
“It ended up being a lot rougher than I had hoped, so it became a frame-off restoration because I like everything really clean and nice looking,” he says. “I spent 30 hours power washing the frame and the underside of the truck.”
With the original 18,000-mile fenders, doors and bed installed on the restored chassis, Karl had the look he wanted. The real work, though, was inside the engine bay. Mireiter initially planned a simple reseal, but like most racers, he “overdoes everything.” The result is a carefully engineered, reliability-focused 800 rwhp VP44-based Cummins build capable of future growth.
Bottom End Prep
Karl tore the engine down to a bare block and kept it at standard bore thanks to a clean cylinder wall. The block received a fresh hone and line hone before being buttoned up with ARP main studs.
For the rotating assembly, he selected Wagler Street Fighter rods paired with mild pistons – a combination proven to live in the 800–1,000 hp range without excessive weight or unnecessary compression changes.
A Hamilton 178/208 cam was installed to broaden torque and provide enough airflow for the GT42 turbo without sacrificing street manners. All wear components are new – bearings, oil pump and all the service-critical hardware were replaced to set a true zero-hour baseline.
Cylinder Head
Up top, Karl wanted strength first, airflow second. “We did not port it. I want to add a ported head in the future,” he admits. “We gave it a race valve job, new springs and crack checked it, and I o-ringed it so it would hold the boost.”
The head uses Hamilton 3-lb. springs and is secured with ARP head studs, with fire-rings cut for sealing in the 50–65 psi boost window the truck now operates in.
Fuel System
The truck initially ran the original 200,000-mile VP44 with 150-hp injectors and still went 12.38 during break-in. But Karl wasn’t going to leave power on the table. In the weeks leading up to UCC 2025, he upgraded to a Scheid Stage 2 VP44 pump, 6×13 injectors and .093” cross-tubes.
“It probably upped the power by about another 300 horsepower,” he notes.
Turbo System
The previous turbo was at the ragged edge of shaft speed, so Karl stepped up to a GT42, sized for ODSS 7.70-index class.
“It’s only about 50 lbs. of boost to run 7.70, but it would do about 65 if you turned it up,” he says.
Karl expects the truck to make around 800 rwhp on fuel alone. Nitrous isn’t currently installed, but the build is arranged so a future kit can be added to help fine-tune drag race interval times.
A Transmission Builder’s Touch
As expected, the transmission is a showcase of RedLine’s capability. “Since I build the transmission, it has all-billet shafts in it,” Karl says. “It’s our high-performance max line pressure valve body. It still shifts in drive, but it’s capable of drag racing or truck pulling.”
Inside is a Goerend triple-disc converter, the same company that builds all of RedLine’s converters and is trusted across their customer base.
Behind the transmission is a heavy-duty transfer case conversion to handle both the shock load of launches and the sustained street use Karl wants from the truck.
A True Racer’s Truck
Though the truck retains all rust-free OEM sheetmetal from his original 2001, everything else received extensive restoration. The paintwork was handled by Rowe’s Rod and Custom in Akron.
The interior is entirely rebuilt as well – all factory Dodge parts, but sourced individually to be as close to new as possible.
Between the frame-off restoration, the meticulous engine build and the proven RedLine drivetrain, Karl Mireiter’s 24-valve Cummins is an ideal example of what a veteran diesel racer builds for himself – strong, clean, functional and ready for both the street and the track.
And just as he did in the early DHRA days, Karl’s still racing what he builds.
Diesel of the Week is sponsored by AMSOIL. If you have an engine you’d like to highlight in this series, please email Engine Builder Editor Greg Jones at gjones@babcox.com.
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