Hydraulic Filter Identification and Service Notes for the Lull 844TT Telehandler

[MikePhua]

The Lull Legacy and the 844TT’s Role in Material Handling
The Lull 844TT telehandler was part of a series of rough-terrain forklifts designed for construction sites where reach, stability, and maneuverability are essential. Lull, originally founded in the mid-20th century and later acquired by JLG Industries, became known for its unique horizontal boom traversal system, which allowed operators to move loads forward and backward without repositioning the machine. The 844TT, with its 8,000 lb lift capacity and 44-foot reach, was a staple on framing crews, masonry sites, and steel erection projects throughout the 1990s and early 2000s.
Unlike conventional telehandlers, the Lull’s traversing boom added a layer of precision that made it ideal for placing materials in tight spaces or adjusting load position mid-lift. The 844TT was powered by a diesel engine—typically a Cummins or John Deere variant—and featured a robust hydraulic system that controlled lift, tilt, traverse, and steering functions.
Terminology Annotation

• Telehandler: A telescopic handler or boom forklift used for lifting and placing materials at height.
  
• Traversing Boom: A boom system that allows horizontal movement of the carriage independent of the chassis.
  
• Hydraulic Filter: A component that removes contaminants from hydraulic fluid to protect pumps, valves, and cylinders.
  
• Spin-On Filter: A type of hydraulic filter that screws directly onto a threaded port, commonly used for ease of replacement.
  

Hydraulic Filter Identification Challenges
One of the most common service issues with older Lull 844TT units is identifying the correct hydraulic filter when the original part number is missing or illegible. Over time, paint wear, oil exposure, and aftermarket replacements can obscure filter markings, leaving technicians guessing.
To resolve this, technicians typically:

• Reference the machine’s serial number (e.g., 3AW02476) to match parts catalogs
  
• Measure the filter’s thread size, diameter, and gasket profile
  
• Cross-reference with known OEM suppliers such as Baldwin, Fleetguard, or Donaldson
  
• Inspect the hydraulic reservoir and filter head for stamped part numbers or casting codes
  

In one framing crew in Louisiana, a technician encountered a missing filter label on a 844TT. By measuring the thread pitch and comparing it to archived JLG service bulletins, they identified the correct replacement as a Baldwin BT839-10, restoring full hydraulic function after a fluid flush.
Recommended Hydraulic Filter Specifications
While exact filter models may vary depending on engine and hydraulic configuration, typical specs for the Lull 844TT include:

• Thread size: 1-1/16"-12 UN
  
• Micron rating: 10–25 µm nominal
  
• Flow rate: 15–25 GPM
  
• Bypass valve: 15 psi
  
• Seal type: Nitrile or Viton depending on fluid type
  

Suggested replacements:

• Baldwin BT839-10
  
• Fleetguard HF6553
  
• Donaldson P550839
  

Always verify compatibility with the hydraulic fluid used—typically ISO VG 46 or VG 68 depending on climate—and ensure the filter meets or exceeds OEM pressure ratings.
Service Tips and Preventive Maintenance
To maintain hydraulic system health:

• Replace the hydraulic filter every 500 hours or annually, whichever comes first
  
• Use only clean, sealed containers when adding fluid
  
• Inspect hoses and fittings for leaks or abrasion every 250 hours
  
• Flush the system if contamination is suspected or after major component replacement
  
• Keep a log of filter changes and fluid top-offs for tracking performance
  

In a steel erection crew in Nevada, implementing a strict 500-hour filter change schedule reduced hydraulic pump failures by 60% over two years, saving thousands in downtime and repair costs.
Final Thoughts
The Lull 844TT remains a respected telehandler in the construction world, especially for crews that value precision and reach. While parts identification can be tricky on aging machines, understanding hydraulic filter specifications and service protocols ensures continued reliability. With proper maintenance and attention to detail, the 844TT can continue lifting, traversing, and placing with the same confidence it delivered decades ago.
In the hum of hydraulics and the reach of steel, the Lull 844TT proves that thoughtful engineering and diligent service keep even legacy machines working strong.