Sumtiomo SH120 Swing Gearbox 2nd Planetary Carrier Spider With Sun Gear Assy For Excavator Parts

Sumitomo SH120 Swing Gearbox 2nd Planetary Carrier Spider With Sun Gear Assy For Excavator Parts

Product Overview

On a 12‑ton class machine like the Sumitomo SH120, the swing drive does more work per hour than most operators realise — short swings, constant repositioning, bucket‑and‑turn cycles on confined urban sites. The second‑stage planetary carrier spider and sun gear assembly sits at the torque end of that drive, receiving the reduced rotation from the first stage and multiplying it one final time before the ring gear turns the upper structure. Because this is the last gear step, it carries the heaviest load in the box, and on a compact machine that load is delivered in sharp, frequent bursts. Over time, the sun gear teeth and spline surfaces pit or fret, the pin bores in the carrier ovalize, and the spider web can distort under repeated shock. The operator experiences it as a low grinding note during rotation, a weakening of swing power under load, and increasingly uneven movement — sometimes with a detectable "catch" at the same point in every revolution. This aftermarket assembly renews that final stage to original geometry, protecting the ring gear and avoiding the full cost of a swing reducer exchange on a machine that still has years of work left.

Technical Specification

Core Advantages

1. Final‑stage hardening where the heaviest torque lands The second stage endures the peak torque of the swing drive, so its sun gear and spline surfaces are carburized and hardened to resist pitting and fretting under sharp, repetitive loading — the exact duty pattern of compact‑class machines working in tight spaces.
2. A carrier that keeps the ring gear safe If the spider distorts, the planets run out of line and start cutting into the ring gear — the single most expensive part in the reducer. Forged, stress‑relieved construction holds the pin bores true, so the ring gear keeps a clean, even mesh and a full service life.
3. Clean, controlled rotation for noise‑sensitive sites A worn second stage announces itself with a low growl on every rotation. Ground tooth profiles and verified clearance keep the final drive turning quietly and evenly, which is a real advantage on residential and commercial sites where machine noise matters.
4. A verified fit that keeps downtime to a service slot Key dimensions are checked against the drawing and recorded before shipment, so installation is a direct swap onto the original footprint — no machining, no fitting work, and no extended stand‑still for a machine that earns by the hour.
5. A cost‑controlled path to keeping older machines running For an SH120 that is otherwise sound, renewing just the second‑stage assembly is far cheaper than replacing the whole reducer, and it extends the machine's working life predictably. Single units, trial samples and fleet quantities are all easy to arrange.

Manufacturing & Quality Control

The production route is fully traced: steel composition check, forging, stress relief, precision machining, carburizing and finish grinding are all logged per batch. Final inspection covers spline gauging, pin‑bore position and size, tooth profile, hardness and a no‑load rotation test on sampled units. Approved parts are oil‑protected, shock‑cushioned and packed in fumigated wooden cases for international freight. Sample orders, repeat supply and scheduled wholesale are all supported.

Frequently Asked Questions

• Q1: What are the first signs that the second‑stage assembly is failing?
• A: Typically a low grinding noise during rotation, weaker swing power when the bucket is loaded, and an uneven or "catching" movement. Metal particles in the swing oil confirm that an internal inspection is due.
• Q2: Should I also replace the ring gear with this assembly?
• A: Only if the ring gear shows visible wear. If the failure was caught early, the ring gear usually survives; inspecting it during the overhaul is the safe way to decide.
• Q3: Does this item suit machines with different hydraulic swing motors?
• A: The unit follows the mainstream SH120 configuration. Different build periods may vary, so please provide your machine serial number or the old part number and we will confirm compatibility.
• Q4: Can you supply this assembly with a measurement report?
• A: Yes — dimensional reports can be provided on request for batch orders, giving your workshop a documented baseline for installation and future wear comparison.