Resolving Track Tension Mysteries on the Cat 307SSR (Gray‑Market)

[MikePhua]

Understanding the Track-Tension System
The Cat 307SSR excavator uses a grease-pressurized cylinder (track adjuster) to maintain correct track tension. This cylinder applies force to an idler assembly, pushing it outward to tighten the track. The tensioner is critical for safe, efficient operation.
Those working on gray‑market or lightly used units often find extreme rust or corrosion binding the adjuster components, making it impossible to tension tracks despite heavy greasing.
Common Signs and Diagnostic Clues
A typical symptom: the cylinder accepts grease under pressure but fails to move the idler or cylinder piston. Grease may simply back out when turning the jam nut, indicating internal leakage or rusted seals.
Experts emphasize that internal seal failure or piston binding is far more likely than insufficient grease delivery in tensioners that refuse to advance.
Expert Insights from the Field
Several seasoned mechanics have shared their experience:
“That’s very common. Your grease gun makes about 10,000 psi—if that doesn’t shift it, a Porta‑Power won’t either. I cut the end off the cylinder, pressed the piston out, and rewelded it. Or replaced it altogether with part no. 1360246.”
Another operator noted:
“I’ve tried to pull them out with D6 dozers and couldn’t budge them. Dirt packs into the piston seals and abrades the rod against the cylinder wall. Rust gets in despite being grease-sealed.”
These insights reinforce that external force alone may fail if parts are seized internally.
Effective Repair Approaches

• Remove the Adjuster Cylinder: Disconnect it from the track frame to gain access. Moving the idler about 6 inches forward can help in removal.
  
• Disassemble or Replace: Disassembling the cylinder—by cutting off the rod end and pressing out the piston—is one route. For reliability and economy, replacing the cylinder with a new unit is often recommended.
  
• Inspect Idler and Yoke for Rust: If rust binds the entire idler assembly, the adjuster cylinder may not be the sole issue. A thorough inspection of the yoke and frame components is advised.
  

Maintenance and Prevention Tips

• Regular Lubrication: Even idle machines benefit from occasional movement or greasing to prevent seals from embrittling and rods from developing corrosion.
  
• Protect from Moisture and Contamination: For units in humid or salty environments, using corrosion-resistant rod coatings or stainless components can limit rust ingress.
  
• Grease Gun Cleaning and Hose Bits: Ensure the zerk fitting is clear and that grease isn't leaking past worn seals—this avoids adding pressure that simply backs out.
  

A Real-World Example
An owner of a gray-market Cat 307SSR left unused for long periods in humid climates found the tensioner seized solid despite massive grease pressure. After removing the adjuster and testing it off-machine by chaining a load and pumping it, the cylinder barely moved—but the chain bent before the seal held pressure. It became clear the internal components were rusted and irreparable. Replacement was the only viable fix.
Conclusion
For Cat 307SSR excavators suffering from unresponsive track tensioners, the most likely cause is internal cylinder seizure—not merely lack of pressure. External force methods often fail. Removing the adjuster, inspecting for internal damage or rusted idler parts, and replacing the cylinder or seals provides the most dependable repair path. For continued reliability, keep components greased, protect against moisture, and service assemblies proactively.