Over-the-Road Semi-Truck Transmissions

Built for the miles. Not just the moment.

Race-proven knowledge, applied to working trucks. We build custom heavy-duty over-the-road transmissions engineered around your truck, your load, and your route — using the same precision we bring to the track.

Built For Durability

Engineered for the demands of heavy, long-haul work.

Smoother Shifting

Setups designed to support cleaner, more consistent shifts.

Driveline-Aware Setup

Angle and geometry considered as part of every build.

Race-Developed Knowledge

Track-tested techniques applied to working trucks.

Built For The Work You Actually Do

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.

What We Learn On The Track, We Build Into Your Truck

Every Saturday, our transmissions are pushed to their limit on the race track. That environment teaches us things a shop bay never could — how components behave under sustained load, how gearing affects real-world performance, and where weak points actually show up.

We apply that same attention to detail to every over-the-road build, so your truck benefits from lessons learned at speed.

Setups Designed To Support Cleaner Engagement

Rough, inconsistent shifting adds unnecessary stress to your drivetrain and wears on the driver over a long day. Our over-the-road builds are set up with the goal of smoother, more predictable shift feel across the gear range.

Shift quality depends on the transmission, clutch setup, driveline condition, and how the truck is operated — so we work through your specifics before we build.

Results vary by application. Smoother shifting is a build goal, not a guaranteed outcome — actual shift feel depends on your specific truck, clutch, and drivetrain condition.

What We Design Every Build Around

We can’t promise outcomes we don’t control — but here’s what every over-the-road build is designed to support.

Lower Operating-Temperature Goals

Setup and component selection are approached with the goal of supporting lower operating temperatures under sustained load. Actual temperatures depend on the application, gearing, maintenance, and how the truck is run.

Depends on application & setup

Durability Under Load

We build with components and tolerances designed to support durability under heavy, sustained load. Long-term life depends on maintenance, driveline condition, and how the truck is operated over time.

Results vary by operation & maintenance

Driveline-Angle Considerations

Driveline angle and geometry are reviewed as part of the build process, with the goal of supporting smoother operation and reduced unnecessary vibration where the setup allows for it.

May help improve overall setup

Setups Built Around Pulling Pups, Not Just Solo Loads

Gravel train and doubles work put a different kind of stress on a transmission than solo hauling — more starts and stops, heavier loaded weights, and constant load changes. We take those specifics into account when spec’ing gear ratios and components.

Tell us how you run — loaded percentage, terrain, pup configuration — and we’ll build a setup around your actual operation, not a generic spec sheet.

Eaton Fuller 13- & 18-Speed Experience

Deep, hands-on experience with the platforms that power the majority of North America’s over-the-road fleet.

13-Speed

EATON FULLER

18-Speed

EATON FULLER

How We Build Your Over-The-Road Transmission

01 Consultation

We talk through your truck, application, route, and how it’s loaded and operated day to day.

02 Spec Review

Current transmission, rear gear ratio, tire size, driveline geometry, and clutch setup are reviewed.

03 Disassemble & Inspect

Full teardown and inspection to identify wear, damage, and components that need replacement.

04 Rebuild & Setup

Precision rebuild using quality components, set up to support your specific application and goals.

05 Test & Verify

Checked for correct operation, engagement, and fit before it ships or leaves the shop.

06 Ready For The Road

Built right, set up right, and ready to go back to work.

THE RIGHT BUILD STARTS WITH THE RIGHT DETAILS

Every custom transmission begins with understanding your truck, racing application, and performance goals. Send us your current transmission, rear gear ratio, tire diameter, loaded or bobtail configuration, and the result you want to achieve. We’ll review your combination and contact you to discuss the right direction for your build.

Frequently Asked Questions

What’s the difference between a race and over-the-road build?

A race transmission is configured for maximum acceleration, rapid shifts, high RPM, and short periods of extreme load. An over-the-road build prioritizes durability, predictable shifting, temperature control, and reliable performance across long distances, changing terrain, and repeated starts and stops.

Do you rebuild 13-speed and 18-speed transmissions?

Yes. We rebuild and configure heavy-duty 13-speed and 18-speed transmissions for over-the-road, vocational, gravel-train, and performance applications. Each build is planned around the truck’s engine, gearing, weight, operating conditions, and performance goals.

Will this lower my operating temperature?

A correctly matched and properly assembled transmission may help reduce excessive heat when the existing transmission setup is contributing to the problem. However, operating temperature is also affected by lubricant, cooling, gearing, vehicle weight, road speed, terrain, ambient temperature, and driveline condition, so lower temperatures cannot be guaranteed from the transmission build alone.

Can you build a setup for gravel-train work specifically?

Yes. We can configure a transmission around gravel-train, doubles, and pup-trailer applications. We consider loaded weight, trailer configuration, terrain, grades, start-and-stop frequency, engine operating range, clutch setup, differential ratio, and tire size when developing the build.

How long does an over-the-road build take?

Build time depends on the transmission’s condition, required parts, machining needs, and the shop’s current workload. After reviewing your transmission and application, we can provide a more accurate estimated completion schedule. Contact us for current lead times before shipping or delivering your transmission.

Do you ship completed transmissions?

Yes. Completed transmissions can be prepared for freight shipping. Contact us before sending your transmission so we can confirm shipping arrangements, delivery requirements, turnaround expectations, and the information that should accompany the unit.

What information do you need to quote a build?

Please provide the truck’s year, make, and model; current transmission model and identification-tag information; engine model and power level; clutch type; differential ratio; tire size; typical loaded weight; trailer or pup configuration; normal routes and terrain; operating RPM range; current problems; and the result you want from the build. Photos of the transmission tag are also helpful.

Does driveline angle really make a difference?

Yes. Incorrect or unequal driveline angles can contribute to vibration, U-joint wear, heat, seal problems, and additional stress on transmission and differential components. Driveline angle should be evaluated together with ride height, suspension position, transmission mounts, driveshaft geometry, and axle placement—especially on modified or heavily loaded trucks.

Your win starts here.

Let’s build a transmission that’s built for your track, your power, and your goals.