Choosing The Correct Track Chains For A Cat 320D Excavator

[MikePhua]

Understanding The Cat 320D Undercarriage Configuration
The Cat 320D is one of Caterpillar’s most widely used 20–22 ton class excavators, often working in quarrying, construction, and utility projects worldwide. Like all crawler machines, its undercarriage configuration directly affects traction, stability, and component life.
A key parameter in that configuration is the number of track links (also called chain links or pads), which determines overall track length and how the chain wraps around the sprockets, rollers, and idlers.
On a standard Cat 320D (non–long undercarriage), the factory configuration uses:

• 45 links per side
  
• Standard track gauge and pitch suitable for the 320D frame
  
• Track groups designed and supplied as a complete assembly from Caterpillar
  

By contrast, a 320DL (long undercarriage) typically uses:

• 49 links per side
  
• A longer track frame and more ground contact area
  

Mixing those configurations or parts intended for one with the other is where many parts-ordering problems start.
Standard Versus Long Undercarriage
In Caterpillar’s product line, the “L” suffix usually indicates a long undercarriage. The long undercarriage variant provides:

• Increased ground contact length
  
• Better stability on slopes or when lifting heavy loads at reach
  
• Slightly different load distribution and wear pattern
  

Because the frame itself is longer, it needs more chain links to wrap properly around the idler and sprocket. This is why:

• Standard Cat 320D → 45-link track chains
  
• Cat 320DL (long UC) → 49-link track chains
  

If you try to mount a 49-link chain on a standard frame, you’ll end up needing to remove links or over-adjust the idler to an extreme position, which can compromise performance, chain tension, and even safety.
Clarifying Conflicting Information From Suppliers
A common real-world scenario looks like this:

• The workshop counts 45 pads on the existing chain.
  
• A supplier insists the machine “should” have 49 pads.
  
• The local dealer offers a 49-link track group and proposes to “take a few out” to make it fit.
  

When this happens, the machine itself is your first and most reliable data source:

• Physically count the links on each side.
  
• Confirm the serial number and exact model (e.g. Cat 320D vs 320DL).
  
• Check the undercarriage frame length visually and, if possible, by measurement.
  

If the machine is a standard 320D with 45 links currently fitted, and the serial number confirms it is not a long undercarriage variant, the 45-link configuration is the correct baseline.
What The Machine Likely Left The Factory With
For a typical standard 320D, the original track group from the factory would be something like:

• Two complete track groups (one per side), each consisting of:
  • One assembled link chain (track chain assembly)
    
  • 45 track shoes (pads)
    
  • Bolts and nuts in matching quantities for the shoes
    

The exact part numbers vary by shoe width and region, but the structure is the same: a 45-link chain matched to the 320D standard undercarriage geometry.
This matters because:

• Undercarriage geometry (distance between idler and sprocket centers, roller spacing, etc.) is designed for a specific pitch and link count.
  
• Deviating too far from that can cause accelerated wear or even derailment of the track.
  

Track Pitch And Why A Few Millimeters Matter
A critical parameter for track chains is the pitch (the center-to-center distance between adjacent pin bores). For many Cat excavators in this class, the OEM pitch is:

• 7.5 inches (approximately 190.5 mm)
  

Aftermarket documentation sometimes lists the pitch in metric as a rounded number, such as:

• 190 mm (7.48 inches)
  

On paper that 0.5 mm difference per link looks trivial, but across a full chain:

• 0.5 mm × 45 links ≈ 22.5 mm total difference
  
• Over 2 cm of cumulative error as the chain wraps around the sprocket and idler
  

If an aftermarket chain is built to a “true” 190 mm pitch instead of being a precise metric conversion of 7.5 inches, you can experience:

• Poor tooth engagement on the sprocket
  
• Abnormal noise and vibration
  
• Accelerated wear of sprocket teeth and bushings
  
• Higher risk of derailment, especially under load or on uneven terrain
  

So when evaluating aftermarket chains, it’s essential to ask the supplier:

• Are the dimensions exact metric equivalents of the OEM imperial specs?
  
• Or are they independent metric designs approximating the OEM?
  

The more the pitch or bushing dimensions deviate, the higher the risk of mismatch.
Risks Of Mismatched Or Improvised Track Length
Simply “taking a few links out” from a longer 49-link chain to make a 45-link assembly may work in some cases, but there are risks:

• Pin/bushing match and pre-load
  The chain is assembled with a specific pin and bushing interference and twist to match wear patterns and bending loads. Cutting out links and rejoining must be done with proper tooling and technique; otherwise you can weaken the joint.
  
• Symmetry of the chain
  Removing the wrong number of links from one side or in the wrong position can affect how the track stretches and runs over rollers.
  
• Tensioning range
  If the assembled length is slightly off due to non-OEM pitch, the track adjuster may end up fully extended or fully retracted to get tension “close,” leaving no adjustment room as things wear.
  

For a hobby or low-hour machine, some owners accept these compromises to save money. For a production machine where downtime is expensive, it is usually wiser to:

• Use correct-spec OEM or high-quality aftermarket chains
  
• Avoid “Frankenstein” assemblies built from mismatched components
  

Production Machine Versus Hobby Machine Choices
When deciding what quality level to buy, consider how the machine is used:

• Hobby / occasional use
  • Lower annual hours
    
  • Undercarriage wear is relatively slow
    
  • Affordable aftermarket components may be acceptable, even if life is shorter
    
• Production / commercial use
  • High annual hours (1,500–2,000+ hours per year is common)
    
  • Undercarriage can constitute 50% or more of lifetime maintenance cost
    
  • Higher upfront cost for OEM or premium aftermarket parts often pays off in:
    • Longer service life
      
    • Fewer breakdowns
      
    • Less downtime and labor
      

A rule of thumb many fleet owners use is that on a busy excavator, saving a few percent on undercarriage parts but losing even one or two days of work to failures is a bad trade.
Practical Steps To Specify The Correct Track
If you’re ordering track groups for a Cat 320D and want to avoid costly mistakes, follow a systematic approach:

• Confirm model and configuration
  • Verify: 320D vs 320DL
    
  • Check the serial number prefix and build configuration
    
• Count the existing links on the machine
  • Count pads/links on each side at least twice
    
  • Standard 320D will typically show 45 links
    
• Measure key dimensions on the current chain
  • Pitch (center-to-center of pins)
    
  • Bushing outside diameter (where it meshes with the sprocket)
    
  • Shoe width (e.g. 600 mm, 700 mm, etc.)
    
• Ask the parts supplier detailed questions
  • Exact pitch (in both metric and inches)
    
  • Whether their specs match Caterpillar’s imperial dimensions precisely
    
  • Whether the chain is compatible with Cat 320D sprockets without modification
    
• Decide your quality tier
  • OEM Cat track groups
    
  • Premium aftermarket with proven reputation
    
  • Economy brands for light-use machines
    

A Short Field Story About Track Mismatch
On a Pacific island project, a contractor imported a standard 20-ton excavator similar to a Cat 320D for foundation work. To save money, he ordered cheaper aftermarket tracks from overseas. The documentation listed:

• 190 mm pitch
  
• 49-link chain for “20-ton excavators” in general
  

The local mechanic shortened the chain to 45 links to fit the frame. At first everything looked fine, but after a few months:

• The sprockets developed sharp hooking on the teeth
  
• The tracks started jumping under heavy digging
  
• Re-tensioning became a weekly chore
  

Eventually they discovered the pitch was slightly off from the OEM spec, and the improvised 45-link chain was always just a bit too long in effective circumference. The contractor ended up buying a full OEM undercarriage set anyway – paying twice to fix what could have been solved by verifying specs from the start.
Caterpillar And The Evolution Of The 320 Series
The Cat 320-series excavators, introduced in the 1990s and evolving into the 320D and later models, became one of Caterpillar’s best-selling medium excavators globally. Over hundreds of thousands of units sold worldwide, undercarriage designs were refined to:

• Balance durability and fuel efficiency
  
• Standardize track components where possible
  
• Offer variants (like long undercarriages) for specific markets and applications
  

Because these machines earned a reputation for reliability, there is a huge global ecosystem of:

• OEM spares
  
• Multiple tiers of aftermarket suppliers
  
• Rebuild and re-bush services for chains and rollers
  

That ecosystem is a benefit – parts availability is excellent – but also a trap if you don’t verify compatibility and specs carefully. Many catalogs list chains “for 320 / 320D / 320DL” without distinguishing link count, pitch tolerances, or intended frame length.
Key Recommendations When Ordering 320D Tracks
To wrap it up, here are practical recommendations:

• Treat 45 links as the reference for a standard Cat 320D undercarriage.
  
• Remember 49 links typically indicates a long undercarriage variant (320DL or similar).
  
• Always confirm the model suffix and serial number before ordering.
  
• Verify track pitch against OEM specs; avoid chains with approximate dimensions if you expect heavy use.
  
• Prefer OEM or high-quality aftermarket chains for production machines.
  
• If a supplier suggests using a 49-link group and “just taking some out,” ask for:
  • Evidence of successful installations on the same model
    
  • Clear statement of pitch and compatibility with Cat sprockets
    

By taking these steps, you greatly reduce the risk of receiving an expensive set of tracks that won’t fit properly or will wear out prematurely – and your Cat 320D will stay productive on the job instead of sitting in the yard with its tracks half-installed.