The Advantages of a 20-Speed Transmission

Using a 20-speed transmission truck can be a great way to increase the efficiency of your fleet and keep up with today’s ever-changing road conditions. If you are in the market for a new commercial truck, you may be wondering if a 20-speed transmission is a viable option.

Although not frequently used today, 20-speed transmissions allow for faster acceleration, higher top-end speeds, safer driving, and overall better efficiency. In this article, we will review the use of 20-speed transmissions in trucks today, details of the Spicer model and shift diagram, as well as compare it to an 18-speed transmission.


How is the 20-Speed Transmission Utilized?

The 20-Speed transmission packs a powerful 5-speed low gear, 5-speed direct gear, and 5-speed high gear combination, enabling you to conquer even the steepest of roads and toughest conditions easily. As mentioned above, the 20-Speed transmission stands out against its counterparts in 4 main categories: speed, acceleration, safety, and efficiency.

Due to the high gear ratio that the transmission contains, the 20-Speed is able to output a wheel torque that is much higher than other transmissions. This allows for trucks to accelerate much faster upon a sudden gear change and eventually reach higher top-end speeds.

While it can provide power and speed when needed, the 20-Speed is often known for its high safety abilities. Its large number of possible gears proves it to be the safest option for driving in tough conditions with numerous elevation changes.

Finally, the 20-Speed is found to be one of the most efficient transmissions known today. Having a variety of different gears allows the vehicle to find the most efficient engine speed and RPM when traveling at a target velocity. By reducing RPMs and horsepower, the transmission is able to conserve fuel in great amounts and output the best performance.

The Spicer Model Transmission

Spicer model transmissions are commercially produced transmissions designed to withstand tough off-highway conditions and produce top-end performance. These transmissions include helical gears that allow for mass noise reduction while also minimizing noise and vibration. Additionally, they contain internal plumbing to help reduce leaks and external maintenance, preventing future maintenance.

Spicer has become very popular nationwide for its superior powershift transmissions that come in three different models. The first is the T Model, an integral transmission and converter assembly mounted directly to the engine. The next is the MT model, where the transmission and converter are mounted remotely from the engine. Lastly, the RT model is a remote-mounted engine with a directly-mounted converter.

The image below shows details for a T-Series 20-Speed Spicer Transmission. The system provides 20 total forward speeds, with ten in each range. As you can see, it provides different recommendations for which gear to engage based on conditions, speed, and RPM. This allows the driver to find the ideal condition, maximizing performance and minimizing fuel use.


The Shift Diagram

Shift diagrams are critical for the operation of commercial trucks, as they explain how to use transmission systems safely and efficiently. These diagrams show commercial truck drivers the best methods for shifting up or down to save fuel, reduce wear on parts, and maximize performance. These help drivers better know and understand their transmissions to increase their handling of the truck.

The diagram below represents the shift diagram of a 20-Speed Spicer Transmission. As you can see, there is a lot going on here. However, as a driver becomes more familiar with the transmission, it can become an easy operation. The sooner a driver knows his complete diagram, the sooner the truck can reach its maximum efficiency and performance.

20-Speed vs. 18-Speed Transmission

To better understand why a 20-Speed transmission may be the right pick for you, we decided to compare it to its counterpart, the 18-Speed transmission. These transmissions are compared in categories of shift ratio, cost, and torque.

Compared to the 20-Speed, 18-Speed transmissions provide a relatively low shift ratio. This leads to limited gear shifting and may result in some jerks due to vibrations on difficult terrains.

In the cost category, the two are very similar but in different ways. The 20-Speed transmission will be a larger up-front cost, as it’s a newer and more innovative product. However, the 20-speed provides higher fuel efficiency when compared to all other transmissions used today. Therefore, it provides a high possibility of saving you money down the road (literally).

Lastly, a 20-speed transmission provides a much greater torque capacity than an 18-speed. The higher gear ratios result in a greater produced wheel torque, providing more acceleration to the truck as a whole. While both transmissions place in the top categories of performance and efficiency, it is clear that the 20-Speed has its advantages.


Although not well known today, the 20-Speed transmission has the necessary tools to make it a popular transmission. Its high efficiency and safety paired with fast speeds and sudden acceleration make it a promising tool for drivers everywhere. Whether you’re looking for a workhorse to help with heavy-duty jobs or something innovative to separate your company from the competition, the 20-speed transmission can be a great choice.