In terms of truck racing performance, engines steal most of the spotlight from the rest of the vehicle’s components. Horsepower output does matter; however, to be effective the force needs to be delivered efficiently to the ground. Today, we are going to focus on the popular drivetrain components for off-road truck racing applications. The drivetrain consists of the transmission, drive shaft, rear differential, axles and rearend housing. To be successful in racing, these components must withstand brutal track conditions and be easily customizable if those conditions change. Let’s start at the beginning.
Click Here to Learn about the Engine Options for Off-Road Stock Truck
Turbo Hydra-Matic 400 Transmission (TH400)
The world of off-road truck racing is filled with bumps, jumps, and all kinds of unexpected challenges. That’s why having a reliable transmission is key to any successful off-road racing vehicle. And when it comes to transmissions, the Turbo Hydra-Matic 400, or TH400, is often the top choice for off-road racers around the world.
Manufactured by the General Motors Company (GM) between 1964 to 1982. The aftermarket industry continues manufacturing these transmissions for performance and leisure applications. There are many conversion kits available to run this GM product on other manufacturer’s powerplants.
A Transmission Built to Last
One of the biggest advantages of the TH400, 3-speed automatic transmission, is its durability. Built to handle the high demands of performance vehicles, making it a perfect fit for off-road racing. Its heavy-duty design means that it can handle the rigors of off-road racing without breaking a sweat. So, if you’re in the middle of a race and find yourself facing a steep hill or a tricky patch of mud, you can trust that your TH400 will help you power through it.
Customization is Key for Truck Racing
Another great feature of the TH400 is its versatility. Customization of this transmission is available to fit the specific needs of your off-road racing vehicle. Whether you need a higher stall torque converter for better acceleration or a specific gear ratio to maximize your vehicle’s performance, the TH400 can be adapted to meet your needs. This level of customization is crucial for off-road racing, where every little advantage can mean the difference between first and second place.
Performance that Speaks for Itself
Of course, the true test of any transmission is how it performs on the track. And the TH400 does not disappoint. Its smooth shifting and reliable performance have made it a favorite among off-road racers for years. When you’re racing off-road, the last thing you want to worry about is your transmission. With a TH400, you can focus on the race and let your transmission handle the rest.
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Spool Differential
When it comes to maximizing traction and performance, spooled differentials are often the go-to choice for serious racers. A spooled differential may be a new term for most people, because it’s not standard equipment on street vehicles. You will most likely see an open or limited slip differential for your commuter, because the increased amount of slip is easier on your tires and other components. For now, let’s dive into why these components are essential for off-road truck racing applications.
A Steady Grip on Victory
One of the main advantages of spooled differentials is the consistent traction they provide. Unlike open differentials, which allow each wheel to rotate at different speeds, spooled differentials lock the wheels together, ensuring they turn at the same rate. This means that if one wheel starts to slip, the other wheel won’t lose power, helping your truck maintain a steady grip on even the most challenging terrains. This consistency can be a game-changer when you’re truck racing through mud, sand, or uneven ground.
Most vehicle classes in Short-Course Off-Road Racing are rear-wheel drive, therefore spooled differentials are essential to avoid being stuck in the mud. We’ll get into why that is at another time. The spooled differential gives rear-wheel drive vehicles half of the technology their four-wheel drive counterparts enjoy. The increase grip does come with a cost, spooled vehicles are hard to turn in the corners of the racetrack. It is why you see these vehicles try to drift around the corners instead of driving through them!
Simplicity and Durability in One Package
Another significant benefit of spooled differentials is their simplicity and durability. With fewer moving parts than other differential types, there’s less that can go wrong, making them a reliable choice for the rigorous demands of off-road truck racing. They are also generally more robust and able to withstand the high stresses that come with aggressive driving on uneven terrains. When you’re in the middle of a heated race, the last thing you want to worry about is your differential failing you.
Customization for Your Truck Racing Needs
Spooled differentials can be customized to suit your specific truck racing needs. Whether you need a full spool for hardcore off-roading or a mini spool for a more balanced performance, there’s an option that’s just right for you. This customization ensures that you have the perfect setup for whatever challenges the race throws at you. You can fine-tune your vehicle to handle anything from steep hills to rocky paths, ensuring you have the upper hand in any racing situation.
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40+ Spline Axle Shafts
As we travel down the drivetrain, the axle shafts are next. Due to the high stress of off-road truck racing on the transmission and the spool, the axle shafts need upgraded too. Your daily driver’s axle shaft spline count is approximately 31 or less, making it very light duty and thin in diameter. In the world of high-performance truck racing, 40+ spline axle shafts are often the preferred choice for racers who want the best for their trucks.
The Powerhouse of Truck Racing
40+ spline axle shafts are like the powerhouse in your truck’s performance toolkit. These shafts have more splines, which are the grooves on the axle shaft that mesh with the differential to transmit torque to the wheels. More splines mean a larger diameter and a stronger shaft, capable of handling the intense pressures of truck racing. The result is a more reliable performance, reducing the likelihood of axle breakage when horsepower and torque numbers are increased.
| Number of teeth | Common Application | Major Diameter | % Change in Diameter | % Change in Strength |
| 28 | GM 10-bolt, 8.8″ Ford | 1.208″ | -6.9% | -19.3% |
| 30 | GN 12-bolt | 1.291″ | — | — |
| 31 | 9″ Ford | 1.333″ | 3.5% | 10.7% |
| 35 | Racing | 1.500″ | 17.2% | 61.2% |
| 40 | Racing | 1.708″ | 34.5% | 143.2% |
Customization for Your Truck Racing Needs
One of the beautiful things about 40+ spline axle shafts is their ability to be customized to meet the specific needs of your truck and your racing style. Whether you need a particular length, spline count, or material, you can find a 40+ spline axle shaft that fits the bill. This customization ensures your truck is always running at its best, no matter what challenges the race throws your way.
Built to Last
When it comes to truck racing, the last thing you want to worry about is your axle shafts failing mid-race. 40+ spline axle shafts are designed to be robust and durable, providing you with peace of mind as you navigate through rough terrains and challenging racecourses. These shafts are built to last, ensuring that your truck is always race-ready and able to handle whatever comes its way.
Ford 9” Rear Axle Housing for Truck Racing
In the realm of truck racing, every component of your vehicle’s drivetrain plays a crucial role in ensuring optimal performance and victory. As we wrap up our discussion on the drivetrain, we conclude where the spool and axle shafts call home: the rear axle housing. When it comes to rear axles, the Ford Motor Company’s 9” rear end reigns supreme. Let’s explore why this rear axle housing is the top choice for truck racing enthusiasts.
Durability that Stands the Test of Time
When it comes to truck racing, the common theme is durability. The Ford 9” rear axle is renowned for its robustness and ability to withstand the rigorous demands of racing. Originally designed to be strong enough to handle the Ford Thunderbird’s 300 HP V8 back in the day. Its design and construction utilize high-quality materials that ensure it can handle high torque and horsepower without batting an eye. With the Ford 9” rear axle, you can rest assured that your truck has the support it needs to perform at its best.
The hypoid offset is one of the greatest features of the great Ford 9-inch rearend. It has more offset than its competitors, which allows the gear to maintain more secure contact. Even though this reduces efficiency of the mechanism, the tradeoff is greater durability for high-stress situations.
Versatility for Any Truck Racing Situation
The versatility of the Ford 9” rear axle housing is another reason it stands out among its competitors. Customization of these Axle housings to fit the specific needs of your truck and racing style is a must. Whether you need a particular gear ratio, limited-slip differential, or any other custom feature, the Ford 9” has got you covered. This level of customization ensures that you have the right setup to tackle any racing challenge that comes your way.
The Ford Motor Company only manufactured these 9-inch rearends from 1957 to 1986. It was standard equipment for many cars and trucks under the Ford banner. The aftermarket industry has picked up the production of their versions of this famous rearend. You can buy or build versions of the Ford 9-inch for any racing format, such as drag, circle-track, on-road, and off-road truck racing. Over the years, these aftermarket companies have found ways to improve the famous 9-inches in racing to support 1000+ HP.
Ease of Maintenance
Another advantage of the Ford 9” rear axle is its ease of maintenance. Its design allows for easy access to the differential and gears, making repairs and gear changing a breeze. This is a significant benefit for truck racing enthusiasts who often need to make quick adjustments or repairs in preparation for a race. The Ford 9” rear axle ensures that you spend more time on the track and less time in the garage. The race team that selects the best gear ratio for the racetrack is the one who usually wins the race! Horsepower cannot make up for poor gear selection.
Successful racers are meticulous with their preparation for off-road truck racing. It takes hours of strategic thinking to find the best setup for a specific racetrack. Horsepower is not the end all be all, the drivetrain is equally important. The engine and drivetrain must be in sync, along with other systems to win the race and stand on the podium!
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