Undercarriage & wear parts
CAT 320 undercarriage parts: identify by serial, not by model name
CAT 320 generations and the serial prefix
The 320 designation covers several build series, and Caterpillar records the build in the serial number prefix rather than in the model name. Two machines both sold as "320" can have different undercarriage dimensions if their prefixes differ.
This is the single most useful piece of information you can give a supplier, and it is the piece most often omitted. "320" on its own gives a supplier a family, not a machine.
Why the parts book is not enough on its own
A parts book maps a part number to a serial range. If you look up a number for a range that is not yours, the drawing will look correct and the part will not fit. The correct order of operations is: establish your serial range first, then look up the number within that range.
Suppliers who quote from the model name are skipping the first step. Suppliers who ask for the prefix are doing it in the right order.
The two measurements that catch most CAT 320 errors
For rollers and idlers: shaft diameter and mounting flange spacing. For sprockets: tooth count and chain pitch. In both cases the measurement confirms what the serial number suggests, and the two together are far more reliable than either alone.
If a supplier quotes you a part without asking for either the serial prefix or these measurements, the price is not yet a price — it is an estimate against a machine family.
The CAT 320 is one of the most widely used 20-tonne excavators, and like the Komatsu PC200 it is frequently ordered for incorrectly. The difficulty is not finding parts — it is identifying which variant of the machine you actually have.
Why the model number alone is not enough
"320" spans several generations with different undercarriage dimensions, and within each generation there are regional builds. Track rollers, idlers and sprockets do not interchange freely across them. A supplier who quotes from "320" alone is guessing.
The three identifiers that actually work
- Serial number prefix. Caterpillar serial numbers carry a prefix that maps to a specific build series. This is the single most useful piece of information you can send.
- Casting number on the worn part — cast into the metal, more reliable than any label.
- Measured dimensions — shaft diameter and flange spacing for rollers; tooth count and pitch for sprockets.
Common mistake: ordering from a parts book alone
Catalogue numbers map to serial ranges. If you look up a part number for a different serial range than your machine, you will get a part that looks right in the drawing and does not fit. Always match the serial range first, then the part number.
What we need to confirm a CAT 320 part
- Full serial number, including the prefix
- Photo of the casting number on the existing part
- Key dimensions for the part type
- Quantity and whether one-off or repeating
Send to alfrun@gmail.com — we confirm the part number and the fitment basis before quoting.
Before you order
Send machine make, model, serial number and a photo of the casting mark. We confirm the part number and fitment basis before any price discussion.
Trademark notice
Machine brand names and part numbers are used only to describe fitment and application. We are not an authorised dealer of any machine manufacturer.
Reviewed by Zhonglei M&E parts desk — export trading partner for undercarriage and wear parts. Last updated 2026-11-13.