17A1211221 / 17A-12-11221 COUPLING KOMATSU

The part numbered 17A1211221, also written as 17A-12-11221, is a drivetrain-related Komatsu component associated with D155-series bulldozers. Public marketplace and catalog references place this number in transmission, torque, damper, and universal-joint-related sections, which shows that it belongs to a high-load mechanical area rather than a simple support item.

From the product images, this part has a splined inner bore, a thick cylindrical upper section, a broad machined mounting face, and a four-bolt outer body. That combination indicates a component designed to connect rotating elements securely while maintaining alignment and stable engagement under heavy operating stress.

At 3GEN Export, we supply this Komatsu coupling as an OEM supplier for customers who need reliable fit, export-ready service, and fast shipping. We deliver all over the world in 5 working days, helping workshops, fleet owners, dealers, and contractors keep their machines working with less downtime.

Product Overview

17A1211221 / 17A-12-11221 is sold in the market as a coupling and is grouped by sellers under transmission and torque parts. One public listing also shows it inside a broader assembly that includes body, flange, shaft, bearing, holder, cover, seal, tube, bracket, and gauge components, which strongly suggests that it works inside a larger drive-related system rather than in isolation.

That context is important for buyers. A coupling in this area is expected to transfer rotational force, maintain position between mating parts, and continue performing under vibration, shock load, and long service hours. In bulldozer applications, small dimensional errors in a powertrain component can create larger problems such as difficult installation, uneven wear, or premature movement in nearby parts.

Why This Part Matters

Komatsu D155 dozers are used in aggressive jobsite conditions including pushing, grading, ripping, earthmoving, stockpile work, and heavy-duty ground preparation. Parts installed in drive-related sections must handle constant torque variation, changing surface resistance, and repeated impact from uneven terrain. Because public sources connect this number with damper and universal-joint-related sections, it is reasonable to treat it as a mechanically important component in the machine’s power path.

For maintenance teams, this means the part should not be viewed as routine hardware. A worn or incorrectly matched coupling can contribute to backlash, vibration, installation trouble, and additional wear on adjoining parts. A correctly supplied replacement helps restore a more secure connection and supports more dependable operation after service.

Visible Design Features

Splined Internal Bore

The inner spline profile is the clearest functional feature in the product photos. This design allows the part to mate with a compatible shaft or driven member and helps transfer torque without slip. In heavy-equipment systems, splined couplings are widely used where reliable rotational engagement is essential.

Thick Upper Collar

The raised cylindrical section around the splined opening suggests a reinforced engagement zone. This kind of geometry usually supports better seating and helps the component manage force around the connection area.

Four-Point Mounting Body

The lower section includes four bolt holes positioned in a balanced pattern. That external mounting layout indicates the part is meant to be fixed securely into a larger assembly while the internal spline connects with a rotating element.

Machined Seating Surfaces

The visible finishing on the main contact faces supports the idea of a precision-machined part. Good surface quality matters in assemblies where seating accuracy and stable contact affect long-term service life.

Compatible KOMATSU Models

Public listings and catalog references connect this number mainly with Komatsu D155-series bulldozers. Commonly referenced models include the following:

• D155A-3

• D155A-5

• D155A-6

• D155A-6R

• D155AX-3

• D155AX-5-A

• D155AX-5

• D155AX-6

• D155AX-6A

• D155AX-7

• D155AX-8

Some public references also show serial-based applicability, including ranges such as D155A-3 S/N 60001-up, D155AX-3 S/N 60001-up, D155AX-5 S/N 70001-up, and D155AX-6 S/N 80001-up. Because Komatsu assemblies can vary by series, specification, and serial break, matching by full machine model and serial number is the safest way to confirm fit before ordering.

Weight in KG

A 3genexport search result lists the part weight as 3.760 kg, while an aftermarket listing shows package weight at 4.09 kg. The difference is likely caused by catalog weight versus packed shipping weight. For website use, the most practical presentation is approximate net/reference weight: 3.76 kg.

Technical Details

Part number

17A1211221

Alternative part number format

17A-12-11221

Product type

Coupling.

Main category in public seller listings

Transmission and torque parts.

Related system references

Damper and universal-joint-related sections on D155-family machines.

Estimated weight

Approximately 3.76 kg.

Application and Function

This component is best understood as a heavy-duty connecting part inside a Komatsu drivetrain-related assembly. The splined center is designed for positive engagement, while the outer mounting body secures the part in place within the surrounding system. In working bulldozers, that kind of part helps maintain force transfer between connected components and supports stable mechanical operation under repeated load.

Because the public assembly listing includes related items such as shaft, bearing, holder, cover, seal, tube, bracket, and gauge assembly, the coupling should be considered part of a larger mechanical group rather than a standalone simple connector. That matters during service because wear in nearby parts may affect the performance of the new component after installation.

Installation Considerations

Confirm machine details first

Before purchase, verify the complete model and serial number. D155 machines include several variants, and public sources indicate that this part appears across multiple generations and serial ranges.

Inspect mating splines

Check the shaft or connected part for spline wear, burrs, or visible deformation. Even a correctly supplied replacement may not perform well if installed against a damaged mating surface.

Review surrounding parts

Because this part works with other drive-related components, inspect nearby bearings, seals, holders, covers, and bolts during repair. Replacing only one item in a worn assembly may not fully restore performance.

Recheck after installation

After the machine returns to service, inspect for abnormal noise, vibration, or unwanted movement. Early follow-up helps catch seating or alignment problems before they become more expensive failures.

Advantages for Buyers

A well-made coupling for a D155-series dozer offers several real-world advantages. First, it can support smoother installation by reducing the chance of forced assembly or mismatch in the spline and mounting areas. Second, it helps protect surrounding parts by maintaining better engagement and more stable load transfer. Third, it supports uptime, which is often the most important factor for contractors and fleet managers.

This is also a commercially strong part number for e-commerce because buyers search it in multiple ways. Some use the full code without hyphens, some use the hyphenated version, and others search by model family or component type. That makes it valuable to build a product page that captures both technical searches and commercial buying intent.

Why Buy from 3GEN Export

At 3GEN Export, we understand that industrial buyers do not just need a product listing. They need a supplier who can identify the part clearly, respond quickly, and support international delivery without unnecessary delays.

We supply 17A1211221 / 17A-12-11221 as an OEM supplier and deliver all over the world in 5 working days. That helps repair teams and procurement managers reduce machine downtime and keep D155-series bulldozers working in tough field conditions.

Our focus is practical: strong export handling, clear product communication, and dependable supply for heavy machinery spare parts. For customers maintaining Komatsu dozers, that combination matters just as much as the part itself.

Final Summary

17A1211221 / 17A-12-11221 is a Komatsu D155-series coupling used in transmission, torque, damper, and universal-joint-related assemblies according to public listings and catalog references. The most commonly referenced compatible models include D155A-3, D155A-5, D155A-6, D155A-6R, D155AX-3, D155AX-5-A, D155AX-5, D155AX-6, D155AX-6A, D155AX-7, and D155AX-8. Published reference weight is about 3.76 kg, while packed listing weight can be slightly higher.

From the images, the part’s splined bore, robust outer body, and four-bolt mounting design match the expectations of a heavy-duty drivetrain connection. For customers looking for reliable supply, 3GEN Export provides this part as an OEM supplier with worldwide delivery in 5 working days.