When to Replace the Undercarriage Before Shipping a CAT 320D
The undercarriage is often the largest repair line on a used 20-ton excavator. Replacing it before shipping can make sense; replacing a serviceable set can waste money. The decision should be based on wear evidence, not on the hour meter alone.
The wear items
| Part | What to look for | Why it matters |
|---|---|---|
| Track shoes | Worn grousers, cracks, missing shoes | Traction and replacement cost |
| Links | Stretch, pin boss wear, cracks | Track tension and sprocket wear |
| Rollers | Leaks, flat spots, loose mounting | Track support and wear |
| Idlers | Worn rim, leaks, play | Track alignment |
| Sprockets | Worn teeth, uneven wear | Drives the track; wears the links |
Judge the set, not one part
A new set of shoes on worn links is not a rebuilt undercarriage. Look at the whole system: shoes, links, rollers, idlers and sprockets wear together. If one part is new and the rest is near the end of its life, the mismatch can accelerate wear.
Ask for a wear estimate as a percentage and the photos behind it. If the seller cannot provide a percentage, use the photos and a mechanic’s opinion.
Replace in China or at the destination?
Replacing in China can be cheaper for parts and labour, and it lets you ship a machine that is ready to work. It also increases the machine’s declared value and the freight weight, and it may not be covered by the carrier’s insurance unless declared.
Replacing at the destination can be better if local parts are cheaper or if the buyer wants to choose the brand. It also means the machine may sit while the parts arrive. Compare the total, not just the parts price.
What to put in the shipping file
Photograph the undercarriage before loading, note the wear estimate and keep the parts invoices if you replace it. If the machine is inspected at the destination, those photos are the baseline.
Also record the track tension and any leaks. A small leak that is not documented before loading can become a dispute after arrival.
How to measure wear
Ask the inspector to measure the track shoe height, the link height, the roller diameter and the sprocket teeth. A photo is useful, but a measurement is better. If the inspector cannot measure, ask for a close-up with a scale reference and a written opinion.
Compare the measurements with the manufacturer’s wear limits if available. If not, use the inspector’s experience and the cost of a new set as the benchmark.
Parts quality
Undercarriage parts vary in quality. Ask what brand and grade the replacement uses. A cheap set may wear faster than the set it replaced. For a machine that will work daily, a reputable aftermarket or OEM set is usually the better choice.
Keep the parts invoice. It is evidence of the replacement when you resell or inspect the machine later.
A note on track tension
Track tension affects wear and should be checked before loading. A track that is too tight or too loose can damage the pins and bushes in transit or during the first days of work. Ask the loading crew to check it and record the setting.
Replace or ship as-is: the math
Do the math in the destination currency, not the FOB currency. A set that costs $4,000 in China may cost $6,000 or more at the destination after freight, duty and fitting. If the machine can ship with a set that has 40% life left, the buyer may be better off running it and replacing locally later.
But a worn set can fail during unloading or the first week of work. The cost of a breakdown includes the lost day, the crane or trailer and the repair. For a machine that must start earning immediately, a pre-shipping replacement can be the cheaper decision even if the parts cost more upfront.
Choose based on the work, not on the parts price alone.
What to record before and after
Photograph the undercarriage before the repair, record the measurements and keep the parts invoice. After the repair, photograph the new set and record the date. That record supports the machine’s history when you resell or inspect it later.
Questions buyers ask
How do I know if the undercarriage needs replacement?
Look at the whole set: shoe wear, link stretch, roller and idler condition, sprocket teeth. A single worn part is not the same as a worn system.
Is it cheaper to replace in China?
Often, but not always. Compare parts, labour, freight weight and the destination’s parts prices before deciding.
Will a new undercarriage increase the machine price?
It can, and it should be declared. A documented replacement is a value item, not a hidden one.
Get the undercarriage photos before you decide.
Send the 320D unit you are considering and ask for close-ups of the shoes, links, rollers, idlers and sprockets. We will confirm availability on WhatsApp.