Quarter-Mile Race Transmissions

Launch. Shift. Cross the Line First.

Drag racing gives a truck one job for roughly a quarter mile: put every bit of power to the ground, cleanly, from the moment the tree drops. We build bobtail drag transmissions engineered around your launch, your ratios, and your finish-line RPM.

 

Maximum Launch

Clutch and ratio setup built to put power down off the line.

Fast Shift Recovery

Tight ratio spacing designed to minimize RPM drop between gears.

Bobtail Drag Setup

Built specifically around the weight and traction of a bobtail run.

Finish-Line RPM Target

Ratios planned to carry the right RPM across the stripe.

A Purpose-Built Transmission For A Very Specific Job

Quarter-mile racing compresses everything that matters about a drivetrain into about 10 to 13 seconds. There’s no time to recover from a bad launch, a slow shift, or a ratio that’s wrong for your setup — every part of the transmission has to work together from the tree to the stripe.

We build quarter-mile race transmissions the same way we approach every race build: CNC-machined internals, Eaton Fuller based platforms, and ratios planned specifically around your truck, your class, and your track.

Eaton Fuller Transmission Specialists Working on Heavy-Duty Semi-Truck Drivetrain Components

Built Around Running Without A Trailer

Quarter-mile competition runs bobtail — no trailer, less weight, less traction over the drive wheels. That changes almost every part of the setup compared to a loaded build: gearing, clutch engagement, and how aggressively the truck can put power down without spinning.

We tailor the entire package around your bobtail weight and configuration rather than adapting a loaded-truck setup to fit.

Setups Designed To Put Power Down Without Losing It

The launch sets the tone for the entire run. Too aggressive and you lose traction; too soft and you leave time on the table. We work through clutch engagement and launch strategy with the goal of supporting a strong, controlled launch that gets power to the ground.

Launch performance depends on your specific truck, tune, driver technique, and track surface — so this is always a conversation, not a one-size formula.

Traction conditions vary by track surface, weather, and truck setup. Clutch recommendations are built around your typical conditions, not a guarantee of results on any given day.

Ratio Progression, Shift Recovery & Finish-Line RPM

Three details that separate a fast quarter-mile pass from a slow one — all planned into your build.

Ratio Progression

Each gear is planned to build on the last, keeping the engine climbing efficiently through the run instead of falling out of the power band between shifts.

Planned around your engine & class

Shift Recovery

Tight, well-planned gear spacing is designed to minimize the RPM drop on each shift, so the engine spends more of the run in its usable power band.

Depends on driver & shift timing

Finish-Line RPM

Top gear is selected with a target finish-line RPM in mind, so you're pulling hard through the stripe instead of running out of gear early or being over-geared late.

Target, not a guaranteed result

The Two Numbers That Change Everything Else

Tire diameter and differential ratio determine how every transmission gear translates into actual road speed. Get either one wrong and even a well-built transmission won’t deliver the shift points or finish-line RPM you’re after.

We factor your exact tire diameter and rear gear ratio into the build from the start — and you can run your own numbers any time using our Gear Analyzer.

Semi-Truck Racing Transmission Components Being Serviced by Mechanics at Jimmy's Custom Speed Shop

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 RIGHT BUILD STARTS WITH DETAILS THE RIGHT

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 transmission is best for quarter-mile racing?
There is no single transmission that is best for every quarter-mile truck. We typically build from heavy-duty 13- or 18-speed platforms and select the internal components, gear spacing, and rear-section configuration around your engine, weight, tire diameter, differential ratio, class, and target performance.
Can you help me choose the right gear ratios?
Yes. We calculate the ratio combination using your launch requirements, engine powerband, shift RPM, tire diameter, differential ratio, competition weight, and intended finish-line speed. The goal is to keep the engine in its effective RPM range while minimizing unnecessary shifts.
Do you build bobtail-specific drag setups?
Yes. Bobtail trucks have less weight over the drive tires and different traction characteristics than loaded trucks. We plan the gearing, clutch engagement, starting ratio, and shift strategy around the truck’s actual bobtail weight and track conditions.
What clutch works best for a hard launch?
There is no universal clutch setting for every hard-launch application. A properly configured multi-disc slipper clutch can control how quickly power reaches the drive tires, but the correct setup depends on horsepower, truck weight, tire construction, gearing, track preparation, and available traction.
How long does a quarter-mile build take?
Build time depends on the transmission’s condition, required components, machining needs, and the shop’s current workload. Once we review your application and transmission, we can provide a more accurate estimated schedule. Contact us for current lead times before shipping or delivering your unit.
Can you help me hit a specific finish-line RPM?
Yes. We can plan the transmission ratios around a target finish-line RPM using your tire diameter, differential ratio, expected speed, engine powerband, and track distance. Actual results can still vary with tire growth, traction, weather, vehicle weight, and engine performance.
Do you ship completed transmissions to other states?
Yes. Completed transmissions can be prepared for freight shipping to customers outside the local area. Contact us before sending your unit so we can coordinate shipping requirements, delivery details, turnaround expectations, and the information that should accompany the transmission.
What information do you need to quote a build?
Please provide your truck’s year, make, and model; current transmission model and tag information; engine configuration and power level; clutch type; differential ratio; tire diameter; competition weight; racing class; operating and shift RPM; current performance; target elapsed time or finish-line RPM; and the problem you want to correct. Photos of the transmission tag and current setup are also helpful.

Your win starts here.

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