Champion 736 Series 4 with Clark 4800 Transmission: Troubleshooting Reverse Gear Issues

[MikePhua]

Introduction
The Champion 736 Series 4 motor grader, equipped with the Clark 4800 transmission, is a robust machine designed for precision grading tasks. However, operators have reported issues with the reverse gear, where the machine fails to engage reverse, locks up, or jerks during gear changes. This article delves into potential causes and solutions for these transmission-related problems.
Understanding the Clark 4800 Transmission
The Clark 4800 is a powershift transmission commonly used in heavy equipment like motor graders. It allows for smooth shifting between gears without the need for manual clutching. The transmission operates through a series of clutch packs and hydraulic systems that engage and disengage gears based on operator input.
Common Issues and Diagnoses

1. Failure to Engage Reverse
   One of the most concerning issues is the inability to engage reverse gear. Operators have reported that after replacing the clutch pack, the machine fails to move in reverse and may lock up entirely. However, forward gears often function with some irregularities, such as skipping gears or jerking during shifts.
   Possible causes include:
   • Faulty Clutch Pack Installation: If the new clutch pack was not installed correctly, it may not engage properly, leading to issues with reverse gear engagement.
     
   • Hydraulic Pressure Problems: Insufficient hydraulic pressure can prevent the transmission from engaging reverse. This could be due to low fluid levels, a failing pump, or clogged filters.
     
   • Electrical Issues: The Clark 4800 transmission relies on electrical solenoids to control gear engagement. A malfunctioning solenoid or wiring issue could prevent reverse from engaging.
     
2. Jerking During Gear Changes
   Jerking or harsh shifting between gears can be indicative of several problems:
   • Worn or Damaged Clutch Packs: Even with a new clutch pack, if other components are worn or damaged, they can cause erratic shifting.
     
   • Incorrect Fluid Levels or Type: Using the wrong type of transmission fluid or having incorrect fluid levels can affect the transmission's performance.
     
   • Contaminated Fluid: Dirt or debris in the transmission fluid can cause internal components to stick or wear prematurely.
     
3. Skipping Gears
   Skipping gears, where the transmission jumps over one or more gears during shifting, can be caused by:
   • Faulty Valve Body: The valve body directs hydraulic fluid to the appropriate clutch packs. If it's malfunctioning, it may cause improper gear engagement.
     
   • Solenoid Issues: As mentioned, solenoids control gear engagement. A faulty solenoid can lead to skipping gears.
     

Diagnostic Steps
To accurately diagnose and resolve these issues, consider the following steps:

• Check Hydraulic Fluid Levels and Quality: Ensure the fluid is at the correct level and is clean. Replace if necessary.
  
• Inspect Electrical Connections: Verify that all wiring and solenoids are functioning correctly.
  
• Test Hydraulic Pressure: Use a pressure gauge to check that the transmission is receiving adequate hydraulic pressure.
  
• Examine Clutch Packs: Inspect for any signs of wear or improper installation.
  

Conclusion
Transmission issues in the Champion 736 Series 4 with the Clark 4800 can stem from various sources, including hydraulic, electrical, and mechanical problems. By systematically diagnosing each component, operators can identify and rectify the underlying causes, ensuring the machine operates efficiently and reliably.