Decelerator Pedal History and Options for the Caterpillar D5 96J

[MikePhua]

The Evolution of the Caterpillar D5 96J
The Caterpillar D5 96J series, introduced in the early 1970s, represents a transitional phase in dozer design—bridging mechanical simplicity with emerging hydraulic sophistication. Built during a time when Caterpillar was expanding its power shift transmission offerings, the 96J variant of the D5 was equipped with a three-speed powershift gearbox, allowing smoother directional changes and improved operator control compared to earlier clutch-and-brake systems.
Caterpillar, founded in 1925, had by the 1970s become a global leader in earthmoving equipment. The D5 series was particularly popular in forestry, road building, and small-scale mining operations. Thousands of units were sold across North America, Australia, and Africa, with the 96J serial prefix denoting a specific production run tailored for power shift configurations.
Was the Decelerator Standard Equipment
Contrary to common assumptions, not all power shift-equipped Caterpillar dozers came with a decelerator pedal. The decelerator—essentially a foot-operated throttle reduction device—was offered as an optional attachment on many models, including the D5 96J. Its primary function was to allow the operator to momentarily reduce engine RPM without adjusting the hand throttle, facilitating smoother gear changes and more precise maneuvering.
The absence of a decelerator on some machines was not necessarily an oversight. In certain applications, especially where operators preferred full-throttle operation for maximum hydraulic response, the decelerator was considered unnecessary. Some machines were delivered without it to reduce cost or because the buyer specified a simplified control layout.
Throttle Management and Operator Technique
In machines lacking a decelerator, gear changes and directional shifts were performed using throttle modulation. Operators would manually reduce engine RPM via the hand throttle before shifting, then throttle back up once the gear engaged. While effective, this method required skill and timing to avoid drivetrain shock or transmission wear.
Experienced operators developed their own techniques. One anecdote from Missouri recounts a contractor who ran all his Caterpillar machines at full throttle, executing rapid forward-reverse shifts without incident. His aggressive style, while unconventional, was enabled by the robust design of the powershift transmission and the forgiving nature of the torque converter.
However, not all machines tolerated this approach. In colder climates or under heavy load, abrupt shifts at high RPM could lead to clutch pack degradation or input shaft stress. The decelerator mitigated these risks by allowing quick RPM drops without removing hands from the steering or gear controls.
Adding a Decelerator to a D5 96J
Retrofitting a decelerator to a D5 96J is feasible, especially if the machine’s serial number falls within the mid-range production groups. Caterpillar parts books divide the 96J series into three segments:

• 96J1–3587
  
• 96J3588–5261
  
• 96J5262 and up
  

Each group may have slight differences in pedal mounting brackets, linkage geometry, and hydraulic routing. Before sourcing parts, technicians should verify the serial number and consult the relevant arrangement group. Salvage yards and parts traders often carry complete decelerator assemblies, including pedal, linkage, return spring, and mounting hardware.
Installation typically involves:

• Removing floor plates and inspecting for pre-drilled mounting holes
  
• Installing the pedal bracket and linkage arm
  
• Connecting the linkage to the governor control lever
  
• Adjusting return spring tension and pedal travel
  
• Testing for smooth RPM reduction and return
  

In some cases, hydraulic assist may be required if the governor linkage is stiff or obstructed. Operators should also ensure that the added pedal does not interfere with brake or steering clutch operation.
Decelerator Function in Modern Machines
Today’s dozers, such as the Caterpillar D6 XE, feature electronically controlled decelerators integrated into joystick controls. These systems allow programmable engine response, automatic gear selection, and load-sensing throttle modulation. The mechanical decelerator of the 1970s has evolved into a digital interface, but its core purpose remains: to give the operator precise control over engine speed during critical maneuvers.
In fact, Caterpillar’s current Operator Presence System uses decelerator input to determine whether the machine should remain active. If the pedal is released and no other controls are engaged, the system may idle the engine or apply brakes automatically—enhancing safety and fuel efficiency.
Field Experience and Practical Advice
Operators considering a retrofit should weigh the benefits against their operating style. For machines used in grading, finish work, or tight maneuvering, a decelerator can improve control and reduce wear. For bulk pushing or forestry clearing, where throttle remains high and shifts are infrequent, the pedal may see little use.
A South African engineer recalled running a brand-new D5 in the late 1970s with a factory-installed decelerator. He found it invaluable when working on steep slopes, allowing him to feather engine speed while maintaining grip and control. Conversely, a contractor in Oklahoma preferred machines without the pedal, citing simplicity and fewer parts to maintain.
Conclusion
The decelerator pedal on the Caterpillar D5 96J is a nuanced feature—optional by design, situational in value, and reflective of operator preference. Whether installed at the factory or added decades later, it represents a thoughtful solution to throttle management in power shift machines. Understanding its function, history, and retrofit potential allows owners to tailor their equipment to the demands of the job and the habits of the operator.