Hitachi HMGC16 9181123 final drive for Hitachi EX120-1 EX120 midi excavator

EX120‑1 EX120 Final Drive for Excavator spare parts 9181123 HMGC16 Aftermarket

Product Overview

Before the Zaxis line, Hitachi's EX120 was the little workhorse contractors reached for when a 20‑ton machine was overkill — basement digs, pond dredging, site clearing where footprint mattered. The HMGC16 travel motor and reduction box, reference 9181123, tucked inside each track frame, is the unit that keeps these old machines shuffling between jobs. It takes pump flow and trades speed for torque, turning the sprocket slow enough to pull a 12‑ton frame across soft ground. On an EX120 this age, the drive rarely dies suddenly. It whispers first: one track drifts on a straight, the track shell warms after a longer trundle than it should, and a new hum works its way into the floor. Operators tend to nurse it — but by the time a track hesitates on a bank, the piston block has already been shedding swarf into the oil. This aftermarket unit reproduces the HMGC16 as one sealed, test‑run assembly, matching both the early EX120 and the ‑1 build, so the worn drive lifts out and the new one bolts straight back in.

Core Advantages

1. Keeps a legacy 12‑ton machine earning
Original HMGC16 drives for early EX120s grow scarcer every year. This aftermarket unit gives owners a path to keep a still‑useful machine on the job rather than writing it off over a dead track.

2. Even pull between the two tracks
A lapped piston block and valve plate hold pressure internally, so neither track lags. The machine tracks straight across a yard without the operator fighting a sideways tug.

3. Simple, tough gearing that wears slowly
The old HMGC layout has none of the complexity of later drives — just hardened planetary teeth meshing cleanly. No electronics to fail, no sensor to blame, just gears that last when kept sealed.

4. Sealed against the mud of light‑site work
Older EX120s work through long days in muddy yards, puddles and dust. Fresh shaft and housing seals keep that grit out of the lube — the protection that decides whether the drive reaches its next overhaul.

5. A direct, no‑nonsense fit
Flange, studs and ports reproduce the original, so removal and refitting follow the old Hitachi manual. No adapters, no fabrication, no guessing.

Manufacturing & Quality Control

Components are machined to the original HMGC drawing, heat‑treated where wear bites, and assembled in a clean area. Each finished drive runs on a hydraulic stand while torque, leakage and noise are checked; units outside tolerance are reworked before packing. The internals are fogged with preservation oil, ports are plugged, and the unit is crated on dunnage for freight.

Frequently Asked Questions

Q1: Does this fit both the EX120 and EX120‑1?
A: The HMGC16 covers the early EX120 range. Send the machine serial number and we confirm the exact unit — early‑build variants can differ.

Q2: Is this the complete drive?
A: Yes — the hydraulic motor and planetary reduction come as one bolt‑on assembly. The sprocket typically transfers over.

Q3: What symptoms mean the drive is tired?
A: Mismatched track speeds, pulling to one side, a warm or noisy track motor, and hesitation under load. Catch it before swarf spreads through the travel circuit.

Q4: What's the warranty position?
A: Materials and build defects are covered. Damage from dirty oil, debris in the motor, track obstruction, overload or incorrect fitting is excluded. Photograph any arrival damage before uncrating.