【CASE】8x4 Allison 6AT Dump Truck

This 8x4 dump truck, customized by Yunlihong for our customer, is the epitome of our strongest C-series products, internally coded as C84GV54SD13P480A6O. Through intricate and targeted design and improvements, it can handle almost any harsh working conditions. This conclusion is shared jointly by Yunlihong, Dongfeng, and Allison.

This 8x4 dump truck is equipped with a Cummins 13L ISZ series 480 horsepower engine, coupled with an Allison 6AT automatic transmission with a hydraulic retarder. It is also fitted with a rear axle with a speed ratio of 5.92, providing powerful low-speed torque and high-speed performance.

The C84GV54SD13P480A6O is equipped with a Cummins ISZ480-51 engine, which provides a maximum torque of 2330 N.m between 1100-1300 rpm. This engine series also offers options of 460hp, 520hp, and 560hp, with a maximum torque of 2500 N.m, meeting the power requirements of any regulations.

The matched 6AT automatic transmission model is the Allison 4500_PR, with the torque converter matched with TC561. The front axle adopts a 9-ton dual-steering axle, while the rear axle utilizes an 18-ton wheel-edge reduction drive axle with inter-axle differential lock and inter-wheel differential lock. 

The total mass of the C84GV54SD13P480A6O reaches 54 tons, with a maximum speed of 105 km/h. It also offers an 18-ton wheel-hub reduction drive axle with a 6.733 speed ratio, with a maximum speed of 95 km/h.

The tire model is 315/80R22.5, equipped with front-leading and rear-driving tread pattern.

The overall dimensions of the vehicle are 9000×2550×3450mm, with a wheelbase of 1850+2500+1450mm, and a rear overhang of 1100mm. The cargo box adopts a tilted U-shaped structure, with a floor length of 5.6 meters. The lifting cylinder is a Hyva 157, and the cargo box tailgate adopts a dual-cylinder hydraulic lifting structure.

Among these, the most complex and challenging aspect is the design of the electrical system. In China, especially in heavy-duty trucks, almost all vehicles use manual (MT) or automated manual (AMT) transmissions. Automatic (AT) transmissions are only used in a very small number of special engineering vehicles or light-duty RV chassis. This lack of reference from existing products made our task almost entirely original. We started from scratch to redesign both the vehicle body and chassis circuits, and after re-matching, the final result presented a perfect performance.

Based on the customer's requirement for transporting from the mining area to the destination in a single transport environment, which includes short-distance gravel roads in the mining area and long-distance paved highways, and considering the significant temperature fluctuations throughout the year, we have essentially performed a complete redesign of the vehicle.

Trucks in China generally use manual (MT) or automated manual (AMT) transmissions. Because of significant regulatory differences between countries, AMT trucks in China may not necessarily meet the operational requirements of local conditions. Trucks with automatic transmissions (AT) are customized according to the specific usage environments of each user. However, this places high demands on the truck's design team, including chassis layout, circuit system design, and overall vehicle powertrain matching.

Our primary challenge is the harsh road conditions in the mining area, customer needs a as short a wheelbase and ground clearance as possible. Our final solution was a wheelbase of 1850+2500+1450mm, with the minimum ground clearance occurring at the front axle to ensure absolute safety of the chassis's power system. This was an extremely challenging design task because Allison transmissions with hydraulic retarder are much longer than normal AMT and MT transmissions. This resulted in the transmission's lowest point being unable to exceed 200mm from the ground due to the engine's angle, posing significant safety risks with conventional designs, which we deemed unacceptable. As a result, we even redesigned the connection components between the engine and the chassis to ensure the vehicle's drivability and center of gravity height.

Because the Allison 4500_PR hydraulic retarder has 6 gears, including the closed state of the hydrodynamic retarder, totaling 7 gears, conventional hydraulic retarder controller positions interfere with the dashboard. Therefore, we considered multiple solutions. Initially, we attempted to shorten the length of the hydraulic retarder control lever. However, this resulted in imprecise gear control during driving, so we ultimately abandoned this approach. The second solution involved designing the controller on the dashboard. However, due to the large shift stroke of the controller, only an up-and-down shifting method could be selected. This method also made it difficult to precisely control the gears during driving and was prone to accidental activation, so it was also discarded. We even experimented with 3D printing technology in an attempt to solve this problem.

In the end, we redesigned the structure of the dashboard shifting section, placing the hydraulic retarder lever next to the gearbox shifter. Since there is no need to operate the gearbox shifter during driving, the likelihood of accidentally engaging the torque converter shifter is almost zero. This arrangement is very convenient to operate and provides enough space for operation.

Due to differences in the driving position compared to Chinese regulations, the exhaust pipe at the rear of the cabin interferes with the steering system. We redesigned the routing of the engine exhaust pipe and the tail treatment system and bracket to comply with safety and regulations.

The cabin interior is also highly equipped. The vehicle is equipped with four 1080P high-definition night vision cameras, and the driver can view the surrounding environment through a 10-inch multimedia screen inside the cabin. The driver seat is a multifunctional airbag suspension seat, enhancing driving comfort.

In the chassis layout design, we installed almost all relevant components of the chassis and powertrain within limited space, including the TCM and the energy storage tank for the hydraulic retarder. This was extremely challenging in the design process, and we had to redesign pipelines and brackets accordingly. The benefit of this approach is that there is ample space and anchor points on the outer side of the frame to install various equipment, including an electronic fan system specifically for cooling the transmission and hydraulic retarder. At the same time, we ensure the safety of the relevant components of the powertrain. The ground clearance of all parts on the frame is not less than 400mm, and all equipment is not higher than the upper plane of the frame.

This is designed as an independent electronic fan system based on harsh working environments and significant temperature variations throughout the year. It is securely mounted on the outer side of the frame by sturdy brackets. The front of the fan includes a soft dust-proof mesh and a hard splash-proof guard plate with steel plate perforations. At the very front is a 2mm thick splash-proof guard plate (used when the electronic fan system is not in operation). It can also be used to adjust the air intake of the fan, ensuring optimal heat dissipation.

The hydraulic system is capable of autonomously managing the tailgate's opening and closing when the cargo box is not being raised. Simultaneously, the hydraulic system responsible for raising and lowering the cargo box also regulates the tailgate's opening and closing. This configuration is designed to prevent accidents caused by customers forgetting to open the tailgate while raising the cargo box. The operation of the tailgate relies on two compact hydraulic cylinders that can open it to a 90° angle.