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The Sentimental Value of a Classic Pete 359
The Peterbilt 359, especially the 1985 model with the iconic Corvette dash and a 425 hp Cat 3406B engine paired with a 6/4 overdrive transmission, holds a special place in trucking history. Produced from 1967 to 1987, the 359 was Peterbilt’s flagship long-nose conventional, favored by owner-operators for its rugged build and customizable layout. With a wheelbase stretching to 282–285 inches, this particular unit was originally spec’d for long-haul work, not off-road hauling. Yet for some, the emotional attachment to a classic rig outweighs the practicality of buying a purpose-built dump truck.
Fuel and Hydraulic Tank Configuration
One of the first challenges in converting a road tractor to a dump truck is reconfiguring the fuel system. The original setup with dual 150-gallon tanks mounted under the sleeper is excessive for short-haul dirt work and interferes with dump body installation. A more practical solution is to install dual 90-gallon tanks with integrated steps, mounted below the cab. These smaller tanks reduce weight and improve ground clearance.
Some operators opt for split tanks—half fuel, half hydraulic oil—to power the wet kit. While Peterbilt offers factory split tanks, many prefer a dedicated hydraulic reservoir mounted between the frame rails behind the cab. This setup simplifies plumbing and keeps hydraulic fluid isolated from diesel, reducing contamination risk.
Wet Kit and PTO Compatibility
Installing a wet kit on a 6/4 transmission requires careful selection of a PTO (Power Take-Off) unit. While most PTOs are standardized, the auxiliary transmission layout can affect mounting options and gear ratios. The PTO must match the transmission’s torque output and rotational direction. A Chelsea or Muncie PTO with a direct-mount hydraulic pump is commonly used.
Key considerations include:
Adding Pusher Axles and Reinforcing the Frame
To increase payload capacity and comply with axle weight regulations, many conversions include two pusher axles ahead of the tandems. Hendrickson lift axles are a popular choice due to their durability and parts availability. However, adding pushers shifts weight forward, increasing stress on the steer axle.
Upgrades required:
Suspension and Off-Road Limitations
Most OTR tractors use air ride suspension, which lacks the articulation needed for uneven terrain. Pete AirTrac is one of the better air ride systems for dump conversions, but it still falls short of mechanical suspensions like Hendrickson RT or Chalmers in off-road conditions.
To mitigate air ride limitations:
Selecting the Dump Body and Hydraulic Components
Choosing the right dump body depends on the intended use. For dirt work and hauling a D5 dozer, a 14–16 ft rock tub or steel box is ideal. Crysteel and Western offer durable options with integrated hoist systems.
Hydraulic components needed:
Wheel and Tire Configuration
Aluminum wheels reduce weight and improve aesthetics. Super singles on the steer axle offer better flotation and turning radius. All axles should be fitted with matching aluminum rims for consistency.
Recommendations:
A contractor in Wisconsin converted a 377 to a dump and installed an 18,000 lb front axle from a 379. He had to modify spring lengths and bushings using Kenworth components. The truck performed well but required constant attention to articulation and ground clearance.
Another operator in Wyoming shortened his 378’s wheelbase and installed a 90-gallon tank under the passenger door. He emphasized the importance of using 23" diameter tanks to avoid punctures from rocks.
Final Considerations and Practical Advice
Converting an OTR tractor to a dump truck is feasible but rarely cost-effective. Challenges include:
Conclusion
Transforming a classic Peterbilt 359 into a dump truck is a labor of love that demands mechanical skill, fabrication experience, and realistic expectations. While the result may not match the efficiency of a purpose-built dump, it can serve well for light-duty dirt work and equipment transport—especially when built with care and respect for the truck’s heritage.
The Peterbilt 359, especially the 1985 model with the iconic Corvette dash and a 425 hp Cat 3406B engine paired with a 6/4 overdrive transmission, holds a special place in trucking history. Produced from 1967 to 1987, the 359 was Peterbilt’s flagship long-nose conventional, favored by owner-operators for its rugged build and customizable layout. With a wheelbase stretching to 282–285 inches, this particular unit was originally spec’d for long-haul work, not off-road hauling. Yet for some, the emotional attachment to a classic rig outweighs the practicality of buying a purpose-built dump truck.
Fuel and Hydraulic Tank Configuration
One of the first challenges in converting a road tractor to a dump truck is reconfiguring the fuel system. The original setup with dual 150-gallon tanks mounted under the sleeper is excessive for short-haul dirt work and interferes with dump body installation. A more practical solution is to install dual 90-gallon tanks with integrated steps, mounted below the cab. These smaller tanks reduce weight and improve ground clearance.
Some operators opt for split tanks—half fuel, half hydraulic oil—to power the wet kit. While Peterbilt offers factory split tanks, many prefer a dedicated hydraulic reservoir mounted between the frame rails behind the cab. This setup simplifies plumbing and keeps hydraulic fluid isolated from diesel, reducing contamination risk.
Wet Kit and PTO Compatibility
Installing a wet kit on a 6/4 transmission requires careful selection of a PTO (Power Take-Off) unit. While most PTOs are standardized, the auxiliary transmission layout can affect mounting options and gear ratios. The PTO must match the transmission’s torque output and rotational direction. A Chelsea or Muncie PTO with a direct-mount hydraulic pump is commonly used.
Key considerations include:
- PTO mounting flange compatibility
- Pump displacement and flow rate (typically 20–30 GPM)
- Pressure rating (2,500–3,000 psi for dump applications)
- Control valve and cab-mounted switch integration
Adding Pusher Axles and Reinforcing the Frame
To increase payload capacity and comply with axle weight regulations, many conversions include two pusher axles ahead of the tandems. Hendrickson lift axles are a popular choice due to their durability and parts availability. However, adding pushers shifts weight forward, increasing stress on the steer axle.
Upgrades required:
- Replace the front axle with an 18,000–20,000 lb rated unit
- Install dual steering gears for improved low-speed maneuverability
- Upgrade front springs and add a right-side steering ram
- Reinforce the frame with a double rail from the motor mounts rearward
Suspension and Off-Road Limitations
Most OTR tractors use air ride suspension, which lacks the articulation needed for uneven terrain. Pete AirTrac is one of the better air ride systems for dump conversions, but it still falls short of mechanical suspensions like Hendrickson RT or Chalmers in off-road conditions.
To mitigate air ride limitations:
- Install high-speed dump valves to release air quickly during dumping
- Carry spare ride height rods and air bags
- Monitor articulation and avoid uneven loading zones
Selecting the Dump Body and Hydraulic Components
Choosing the right dump body depends on the intended use. For dirt work and hauling a D5 dozer, a 14–16 ft rock tub or steel box is ideal. Crysteel and Western offer durable options with integrated hoist systems.
Hydraulic components needed:
- Telescopic or scissor lift cylinder rated for 20–25 tons
- Control valve with feathering capability
- Hydraulic reservoir with 30–50 gallon capacity
- Return filter and pressure relief valve
Wheel and Tire Configuration
Aluminum wheels reduce weight and improve aesthetics. Super singles on the steer axle offer better flotation and turning radius. All axles should be fitted with matching aluminum rims for consistency.
Recommendations:
- Use 22.5" aluminum rims with hub-piloted mounting
- Select tires with aggressive tread for off-road traction
- Balance load ratings across all axles to prevent overloading
A contractor in Wisconsin converted a 377 to a dump and installed an 18,000 lb front axle from a 379. He had to modify spring lengths and bushings using Kenworth components. The truck performed well but required constant attention to articulation and ground clearance.
Another operator in Wyoming shortened his 378’s wheelbase and installed a 90-gallon tank under the passenger door. He emphasized the importance of using 23" diameter tanks to avoid punctures from rocks.
Final Considerations and Practical Advice
Converting an OTR tractor to a dump truck is feasible but rarely cost-effective. Challenges include:
- Frame reinforcement and suspension upgrades
- Steering geometry and axle swaps
- Hydraulic system integration
- Limited off-road capability and turning radius
Conclusion
Transforming a classic Peterbilt 359 into a dump truck is a labor of love that demands mechanical skill, fabrication experience, and realistic expectations. While the result may not match the efficiency of a purpose-built dump, it can serve well for light-duty dirt work and equipment transport—especially when built with care and respect for the truck’s heritage.
