Custom Transmissions Built for Semi-Trucks That Work Hard and Race Harder.
Engineered for racers. Trusted on the road. Every build is application-specific from quarter-mile launches to loaded, heavy-haul miles and machined by hand for dependable performance.
One shop. One focus. Semi-truck drivetrains.
01
Semi-Truck Applications Only
No passenger cars, no side projects — every hour goes toward Class 8 drivetrains.
02
Race & Over-The-Road
Built for the strip and built for the mile marker — two disciplines, one standard.
03
Eaton Fuller-Based Platforms
Proven cores, upgraded internals, and tolerances held to race-grade specs.
04
Custom Gearing & Clutch Knowledge
Ratios and clutch setups matched to your tires, motor, and event — not guessed at.
Built for Every Type of Competition
We engineer complete drivetrain solutions for competitive semi-trucks.
Slipper Clutch Rebuilding
Heavy Duty Over-the-Road
- Lower Operating Temperatures
- Smoother Shifting
- Heavy Hauling
- Long Life
Semi-Truck Gear Analyzer
Compare tire sizes, differential ratios, transmission ratios, and shift RPM to see exact MPH by gear — then download a branded, printable gearing report.
Built for the miles that don't stop.
From gravel trains to doubles, our over-the-road transmissions are rebuilt to run cooler and shift smoother, mile after mile, load after load.
- Gravel trains
- Doubles configurations
- Heavy commercial hauling
- Cooler operation & smoother shifts
Jimmy's Custom
Racing Oil
High performance lubricants built for the extreme demands of racing and heavy-duty applications.
High Film Strength
Extreme protection under load
Extreme Heat Protection
Built for high-temp performance
Heavy Duty Gear Protection
Maximize gear and bearing life
Real Results. Real Trucks.
FULL-THROTTLE LAUNCH
When the lights drop, there’s no holding back. Raw diesel power, massive smoke, and trucks charging hard down the track.
BOBTAIL LAUNCH
No trailer. No extra weight. Just raw diesel power. Watch this Dodge bobtail launch hard and lay down a serious cloud of smoke on the strip.
LATE-NIGHT WRENCHING
When the work gets tough, the crew keeps pushing. Late-night repairs, heavy equipment, and no shortcuts—just the work it takes to get back on the track.
The builder behind every build.
No call centers, no sales reps — every transmission that leaves this shop has been through Jimmy’s hands, and every customer has his direct line.
01
Race-Derived Knowledge
Lessons learned on the strip get built into every OTR transmission that leaves the shop.
02
Application-Specific Recommendations
Your ratios, clutch, and setup are matched to your truck, your tires, and your event.
03
Custom-Machined Components
When off-the-shelf isn’t good enough, parts get machined in-house to spec.
04
Direct Communication With the Builder
Talk to Jimmy, not a scheduler — every build starts and ends with a real conversation.
Tell Jimmy what you're building.
Racing, hauling, or somewhere in between — send the details and get a build recommendation straight from the shop.