Beschreibung
The most useful thing on this page is a correction. Our incoming parts sheet grouped these three numbers under a piston pump heading. Komatsu’s own parts catalogue lists 840220120 with the subcategory Gear Pump, and the machine’s hydraulic layout is consistent with that. A gear pump and a piston pump are not interchangeable parts, so getting the type wrong is not a wording problem; it is a wrong-order problem.
What is confirmed and what is not
- Manufacturer-confirmed: 840220120 is catalogued by Komatsu as a Pump Assembly in the Gear Pump subcategory.
- Consistent by numbering: the 8402-20-xxx block belongs to the WB backhoe loader hydraulic parts group rather than to a Komatsu piston pump series.
- Trade-established only: the split of 840220098, 840220102 and 840220120 across individual WB models, and any claim that one supersedes another. No supersession chain is documented in the sources we could check.
Variants
| Number | Where it is listed | Evidence status |
|---|---|---|
| 840220098 | WB-series backhoe loaders, earlier build listings | Trade only |
| 840220102 | WB-series backhoe loaders, mid-range listings | Trade only |
| 840220120 | WB140-2 class listings | Komatsu catalogue confirms Gear Pump subcategory |
We publish one page for the three numbers rather than three competing pages, because the type is settled, the machine family is settled, and the only thing unresolved is which serial range takes which item. That is a question answered by your plate, not by a catalogue.
How a gear pump fails on a backhoe
External gear pumps wear in one direction: clearance between the gear tips and the housing grows, so delivered flow falls as pressure rises. The symptom is functions that work acceptably cold and slow down when the oil is hot, often with a noise at high idle. The root cause is nearly always contamination or a suction restriction, which means the replacement is only as durable as the flush that precedes it.
- Sample the oil and inspect the return filter element before ordering.
- Check the suction line and strainer for restriction or a collapsed liner.
- Measure gear pump output at working temperature against the machine specification.
- Confirm the case and shaft drain path is clear; back-pressure finishes the seal.
Unsere seal kit rebuild checklist und Einkaufs- und Spezifikationsleitfaden für Pumpen cover both the rebuild scope and the comparison method.
Montage und Bestellung
Match shaft spline or key, pilot diameter, flange bolt pattern, port thread sizes and rotation against the removed pump, since gear pumps are direction-sensitive. Prime before cranking, change the filter element, and target ISO 4406 18/16/13 for the piston components sharing the circuit. Minimum order one piece. Three to six month warranty on new aftermarket units as stated on your proforma invoice; bench checked and photographed against your order before the wooden case closes, delivery 5 to 8 working days from payment subject to stock. The WB-series piston pumps are on our 708-1U-00112 page; die Reihe befindet sich unter Hydraulikzahnradpumpe und Komatsu Hydraulikpumpe.
