Tier One's 6.7L Cummins Race Truck Build!
The Tier One "Test Bed" Race Truck: The fastest 68RFE in Arizona! 5.795 660' and .128 60'
Where R&D Meets the Drag Strip
At Tier One Transmissions, we don't just build transmissions; we break them, improve them, and race them. Our 6.7L Cummins Race Truck isn't just a show pony—it is the primary research and development tool for our high-performance transmission builds. We started this journey to prove what a 68RFE could do. Now, we are pushing the platform further to chase lower ETs, better launches, and higher reliability under extreme horsepower. Below is the history of our build, from our first 1700HP dyno runs to our current track-focused setup.
Tier One's Race Truck Build Round 1
- ARP 625 Head Studs
- Manton Springs & Retainers
- Manton Pushrods
- Industrial Injection 128% nozzles
- DDP 12mm CP3
- FASS Fuel Systems Fuel Pump
- Stainless Competition Manifold
- Borg Warner S480 Turbo with a Billet Wheel
- Tier One Stage 2 Transmission
- Revmax Billet Triple Disc Torque Converter
- Billet Input Shaft
- Additional Performance Clutches
- Rollerized Sprag
Tier One's Race Truck Build Round 2
While hitting nearly 1700 horsepower with the first iteration of our truck was all well and good, we wanted even more horsepower and torque. To that end, we jumped up the boost pressure with an even bigger turbo and threw even more fuel at the problem, all while rebuilding the motor from the block up with high-strength block, heads, rotating assembly and much more. We paired the new engine build with one of our 68RFE Competition All-Out transmissions that's rated to handle over 1000+ horsepower. Granted, our hope is that phase 2 of our race truck build hits over 2000 horsepower in the hopes that we actually find the limit of our competition transmission and the truck itself. Round 2 Engine Mods:
- D&J Stage 3 Cylinder Head with Billet Side Draft
- D&J Billet Rods
- D&J Billet Pistons
- D&J Machined Block with Billet Girdle
- D&J Billet Front Cover
- DDP 350% Fuel Injectors
- DDP Twin CP3 12mm Pumps
- Fleece Dual Pump Mounting Kit
- Waterman Lift Pump
- Manton Bridges
- ARP 625 Head Studs
- Garrett GTX 91mm Turbocharger
- Steedspeed Competition Manifold
- Tier One 68RFE Competition All-Out Transmissions
- Revmax Billet Triple Disc Torque Converter
- Revmax Billet Input Shaft
- Revmax Billet OD Hub
- Revmax Billet Center Support
- Additional Performance Clutches
- Revmax Promod Sprag
- Tier One Billet High-Pressure Valve Body
- Revmax Billet Flex Plate
- Nitrous Express Maximizer 6 System
- 375 Lightning Solenoids
- 3-Stage System
Tier One's Race Truck Build Round 3
As we chased faster 60-foot times and consistent track dominance, we realized we needed to radically alter the truck's geometry and driveline. To optimize our weight bias for a better launch, we moved the battery, a new blow down tank, and a larger fuel tank to the back of the truck. We also swapped the rear shocks from QA1s to Afcos to help transfer that weight to the rear tires more effectively. The biggest change, however, was removing the 68RFE in favor of a custom 48RE. This new setup utilizes custom gear ratios to keep the truck in the powerband and features a custom valve body strategy where we run main line pressure at 250 PSI, but regulate lock-up pressure to 175 PSI to prevent the torque converter from ballooning under the massive load.
Round 3 Chassis & Suspension Mods:
- Afco Rear Shocks
- Rear-Mounted Battery Relocation
- Rear-Mounted Blow Down Tank
- Rear-Mounted High-Capacity Fuel Tank
Round 3 Transmission Mods:
- 48RE Transmission Conversion
- HD SFI Rated FI Transmission Case Custom Gear Ratios (2.03 1st Gear / 1.36 2nd Gear)
- Bolt-Together Torque Converter
- Tier One High-Pressure Valve Body (250 PSI Main Line) Regulated Lock-Up Pressure (175 PSI)
