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February 20, 2024

PACCAR TX-18, TX-12 & TX-8 Transmissions

PACCAR TX-18, TX-12 & TX-8 Transmissions

PACCAR is well known for building powerful heavy-duty trucks, but what really sets them apart from the competition is their range of TX transmissions. The PACCAR TX-18, TX-12, and TX-8 are all well regarded within the heavy-duty industry. Although all three are viable all-around options, you’ll likely find that each transmission will thrive under different circumstances. For those that are looking to purchase a heavy-duty PACCAR truck but are facing the tough task of choosing between three viable transmission options, you’ve come to the right place.  

PACCAR TX-18 transmission 

The PACCAR TX-18 is one of PACCAR’s newer transmission options. With a double countershaft design, helical gears, and massive bearings, the TX-18 is a durable option designed to handle even the toughest of jobs. With a torque capacity of 1,850 lb-ft and a maximum operating weight of 140 thousand pounds, the TX-18 is one of the toughest transmissions on the market. 

To ensure excellent performance in all driving situations, the TX-18 uses optimized gear ratios, extreme-duty clutches, 18 forward gears, and 3 reverse gears. You’ll find that the TX-18 makes it easy to control clutch slip, which in turn maximizes maneuverability. When paired with MX engines, the TX-18 is one of the smoothest transmissions on the market. With that in mind, the TX-18 is more than capable of heavy on-road hauling and light off-road hauling. 

Hardware-wise, the TX-18 is a variation of the Endurant automated manual transmissions developed by Eaton and Cummins Inc. Do keep in mind that the TX-18 exclusively couples with Paccar's MX11 and MX13 engines since PACCAR provides all of the required software, calibrations, and integration. For drivers that do a lot of off-highway hauling, the TX-18 Pro may be better suited, for it’s designed for use in road graders, wreckers, large dump trucks, and logging big rigs. 

PACCAR TX-12 transmission 

The PACCAR TX-12 is one of PACCAR’s more capable transmissions and is generally regarded as being the predecessor to the TX-18. With a torque capacity of 1,850 ft-lb and a maximum operating weight of 110 thousand pounds, the TX-12 is a heavyweight within the heavy-duty hauling industry. 


The PACCAR TX-12 has the finest low-speed agility and the widest range of gear ratio coverage. In addition to being completely integrated with the PACCAR MX Engines, the purpose-built automatic gearbox is also the lightest 12-speed transmission in its class, thanks to its sturdy aluminum casing. Not to mention the internal electrical system significantly reduces maintenance requirements by limiting wire and connection exposure and corrosion. 

The PACCAR TX-12 is optimized for use along PACCAR’s MX engines and their DX 40 axles. Due to their lightweight stature and durable design, many consider the TX-12 to be more of an investment than a purchase. 

PACCAR TX-8 transmission


The PACCAR TX-8 automatic transmission's cutting-edge design offers efficiency,  performance, and dependability, all wrapped up in one package. With optimized gear ratios and a strengthened heavy-duty clutch, you can rest assured knowing the TX-18 will shift smoothly when under even the heaviest of loads. With fewer moving parts and no external components, you can anticipate smooth, quiet operation, superb vehicle responsiveness, and durability at a level never seen before. 

Final Thoughts

Although the TX-18, 12, and 8 are all high-quality options, the right option may be simply what fits you best. Whether you’re looking for an on and off-road powerhouse like the TX-18 pro, or a modest on-road hauler like the TX-12, you can rest assured knowing a PACCAR transmission will suit you well. If you’d like to join in on the conversation, be sure to leave a comment below. 

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