Lull 644D-34 Transmission Issue: Troubleshooting and Solutions

[MikePhua]

Introduction
The Lull 644D-34 is a versatile telehandler widely used in construction and heavy-duty applications. However, like any piece of machinery, it is not immune to issues. A common concern that owners and operators face is transmission-related problems. This guide provides an overview of a transmission issue with the Lull 644D-34 and offers troubleshooting tips to help resolve the problem.
Problem Overview
The main issue reported with the Lull 644D-34 is a malfunctioning transmission that can affect the machine’s ability to shift gears, causing a loss of power or even complete transmission failure. Operators may experience difficulty when trying to change from forward to reverse, or vice versa, or there might be a general hesitation when engaging the transmission. The issue can also lead to erratic shifting or slipping between gears.
Potential Causes
Several factors could contribute to transmission problems in the Lull 644D-34, including:

1. Low Transmission Fluid Levels: Insufficient fluid levels are a common cause of transmission issues. Low fluid can result in poor lubrication and inadequate hydraulic pressure, which can lead to improper shifting and potential damage to the transmission.
   
2. Dirty or Contaminated Fluid: Over time, transmission fluid can become contaminated with debris or moisture. This can cause the fluid to lose its effectiveness, resulting in poor performance and potential wear on the internal transmission components.
   
3. Faulty Solenoids or Sensors: Modern telehandlers like the Lull 644D-34 use solenoids and sensors to control the transmission. If these components are malfunctioning, the transmission may fail to operate correctly, affecting shifting performance.
   
4. Damaged Transmission Pump: The transmission pump provides hydraulic pressure to the transmission system. If the pump becomes worn or damaged, it can result in poor performance and even cause the transmission to stop working entirely.
   
5. Worn or Broken Gears: Over time, gears inside the transmission can wear down due to continuous use. If the gears become excessively worn or break, they may cause slipping, difficulty shifting, or failure to engage.
   
6. Electrical Issues: The Lull 644D-34’s transmission system is electronically controlled. Any electrical issues, such as a faulty wiring harness or damaged connections, can disrupt the communication between the control system and the transmission.
   

Troubleshooting Steps
To identify and resolve the transmission issue, follow these troubleshooting steps:

1. Check Transmission Fluid Levels: Start by checking the transmission fluid levels. Ensure that the fluid is at the correct level according to the manufacturer’s specifications. If the fluid is low, top it up with the recommended type of transmission fluid.
   
2. Inspect the Fluid Quality: Remove the dipstick or check the fluid through the filler cap. If the fluid appears dirty, has a burnt smell, or is contaminated with debris, it is time for a fluid change. Replace the fluid and the filter if necessary.
   
3. Test the Solenoids and Sensors: Check the solenoids and sensors responsible for controlling the transmission. Use a diagnostic tool to scan for any error codes that may indicate malfunctioning solenoids or sensors. If any errors are found, the faulty components should be replaced.
   
4. Examine the Transmission Pump: Inspect the transmission pump for any signs of wear or damage. If the pump is not delivering the necessary hydraulic pressure, it may need to be repaired or replaced.
   
5. Inspect the Gears: If the transmission fluid and pump appear to be in good condition, inspect the gears inside the transmission for signs of wear or damage. If any gears are found to be broken or excessively worn, they will need to be replaced.
   
6. Check Electrical Connections: Inspect the wiring harness and electrical connections related to the transmission control system. Look for any loose, corroded, or damaged wires. Tighten or replace any faulty connections.
   

Conclusion
Transmission issues in the Lull 644D-34 can stem from a variety of causes, ranging from low or contaminated fluid to faulty solenoids and sensors. By following the troubleshooting steps outlined above, operators can identify and resolve many of the common transmission problems with this telehandler. Regular maintenance, including fluid changes and system inspections, is key to preventing future issues and ensuring the machine’s optimal performance. If the problem persists after completing these steps, it is advisable to consult with a professional technician for a more in-depth diagnosis and repair.