Eaton Fuller 13-Speed & 18-Speed
Whether you’re running a 13-speed on mixed terrain or an 18-speed under heavy sustained load, we’ve rebuilt, set up, and raced Eaton Fuller based transmissions for years. Over-the-road or race application — we build around your specific platform and your specific job.
Years Of Hands-On Work
Deep, practical experience across both platforms.
Over-The-Road & Race
Built for daily hauling or built to win — same platform, different setup.
Custom Gear Ratios
Gearing planned specifically around your application, not a stock chart.
Independent Builder
Not factory-affiliated — just deep, real-world platform knowledge.
Eaton Fuller® is a registered trademark of Eaton Corporation. Jimmy’s Custom Speed Shop is an independent transmission builder and is not affiliated with, sponsored by, or authorized by Eaton Corporation. “Eaton Fuller” is used here descriptively to identify the transmission platforms we build, rebuild, and set up.
Why The Eaton Fuller Platform Is Where We Live
Eaton Fuller based transmissions are the backbone of heavy-duty trucking across North America — proven, well-documented, and available in configurations that suit everything from daily long-haul freight to purpose-built race applications.
We’ve spent years working inside these platforms: rebuilding worn units, machining custom internals, and setting up gearing for jobs ranging from gravel trains to the quarter mile. That depth of platform-specific experience is what lets us build a transmission around your exact application instead of a generic spec.
- Years of hands-on rebuild and setup experience
- Comfortable across both 13-speed and 18-speed platforms
- Applied to both over-the-road and race applications
13-Speed vs. 18-Speed: Which Fits Your Job?
13-Speed
- Well suited to mixed terrain and varied grade routes
- Simpler shift pattern for high-mileage, daily-driver use
- Common choice for general freight and regional hauling
- Rebuilt with CNC-machined internals where applicable
18-Speed
- Tighter gear spacing for heavier, sustained hauling
- Built with the goal of keeping engine RPM in range under load
- Strong fit for gravel train, heavy-grade, and race applications
- Rebuilt to correct tolerances, component by component
Eaton Fuller Platforms Built For The Long Haul
For over-the-road applications, we rebuild Eaton Fuller based 13- and 18-speed transmissions with the goal of supporting smoother shifting, durability under load, and gearing matched to your route — whether that’s regional freight, gravel trains, or heavy hauling.
- Gearing planned around your route and load profile
- Rebuilt to support long-term reliability under daily use
Eaton Fuller Platforms Built To Compete
The same platform experience carries directly into our race builds. Quarter-mile, uphill, loaded, bobtail, and sled-pulling transmissions all start from Eaton Fuller based platforms, rebuilt with CNC-machined internals and set up specifically for your class and competition style.
- Custom rear sections and race-specific gear ratios
- Built and raced by a team that competes themselves
Ratios Built Around Your Truck, Not A Catalog
Stock gear charts are a starting point, not a finish line. We plan custom gear ratios around your engine, tire diameter, rear gear ratio, and intended use — whether that means closer spacing for sustained pulling power or taller gearing for higher-speed applications.
Every custom ratio set is discussed with you directly and can be modeled ahead of time using our Gear Analyzer.
- Ratios planned around your specific engine and application
- Custom rear sections available for race applications
- Model your setup before committing to a build
Why Application Information Matters
| Information | Why It Changes The Build |
|---|---|
|
Loaded vs. Bobtail |
Changes weight, traction, and ideal gear spacing significantly. |
|
Tire Diameter |
Directly affects how each gear translates into road speed and RPM. |
|
Rear Gear Ratio |
Works together with transmission ratios to set overall gearing. |
|
Racing Type or Route |
Drag, hill climb, pulling, and over-the-road each call for different ratio progressions. |
|
Engine & Horsepower |
Determines the usable power band we’re planning gearing around. |
How We Build Your Eaton Fuller Based Transmission
01
Consultation
We learn your truck, platform, application, and goals in detail.
02
Spec Review
Current transmission, rear gear ratio, tire size, and engine specs are reviewed.
03
Disassemble & Inspect
Full teardown and inspection to identify wear, damage, and needed components.
04
Custom Rebuild
CNC-machined internals, precision assembly, and gearing set up for your application.
05
Test & Verify
Checked for correct operation and engagement before it leaves the shop.
06
Delivered Ready To Work
Shipped or picked up, built right and set up right.
Model Your Eaton Fuller Setup Before You Build
Use our Gear Analyzer to calculate tire size, differential ratio, shift points, and MPH by gear for 13-speed or 18-speed configurations — then compare setups before you commit.
