APP 01

EXCAVATOR
TRAVEL FINAL DRIVE

Planetary gear specification: M4–M8, 18CrNiMo7-6 carburized, DIN 6–7, two-stage planetary (stage 1 ratio 5:1–7:1, stage 2 ratio 5:1–8:1, total 25:1–56:1), output torque 8,000–150,000 Nm, sealed-for-life oil fill with labyrinth and lip seal shaft entries, service factor 2.0. The excavator travel final drive is the highest-stress planetary gear application in construction equipment — it transmits the full machine drawbar pull (up to 300 kN for a large excavator) through two planetary stages to the sprocket that drives the undercarriage track. The gearbox is integrated into the undercarriage frame directly behind the sprocket, in a location that is continuously exposed to mud, water, and abrasive fine particles. Sealed-for-life design with high-viscosity gear oil (ISO VG 220 in summer, VG 150 in cold climates) and triple shaft sealing (labyrinth + two lip seals + mud seal on the sprocket shaft entry) is the standard. The planetary gears must withstand the peak stall torque when the track is held stationary against maximum hydraulic pressure — for a 20T excavator, this peak stall torque is typically 2.5–3× the rated travel torque. Korea Ever-Power supplies excavator final drive planetary gear sets for 5T through 70T class excavators in both the stage-1 and stage-2 gear positions, as matched sets with ring gear, planet gears, planet carrier, and sun gear.

APP 02

CRANE SLEWING
RING DRIVE

Planetary gear specification: M4–M8, 18CrNiMo7-6 carburized, DIN 6, single-stage planetary ratio 4:1–8:1 (drives a spur gear pinion that meshes with the slewing ring internal tooth), output torque 20,000–80,000 Nm, sealed gearbox, service factor 1.5. Mobile crane slewing drives rotate the crane superstructure (boom, counterweight, operator cab) around the slewing ring — the large-diameter ring gear that sits between the superstructure and the carrier. The planetary gearbox sits inside the superstructure, driving a spur pinion that meshes with the internal teeth of the slewing ring. The slewing drive sees a relatively smooth torque (hydraulic actuation without impact), but must withstand the dynamic loads from boom swing momentum when the slewing motion is arrested — an operator stopping a loaded boom swing abruptly generates a torque spike at the drive from the moment of inertia of the swinging load. Korea Ever-Power’s crane slewing planetary gear sets are designed with this dynamic arrest torque factored into the tooth bending fatigue calculation. Planet gear bore H6 for needle roller bearing — the needle roller bearing maintains planet shaft deflection below 0.01 mm under maximum slewing torque, maintaining the planet-ring gear contact pattern within the designed load-sharing tolerance.

APP 03

COMPACT TRACK
LOADER WHEEL HUB

Planetary gear specification: M3–M5, 20MnCr5 or 18CrNiMo7-6 carburized, DIN 7, single-stage planetary ratio 4:1–6:1 (inside wheel hub, integrated with hydraulic wheel motor), output torque 3,000–12,000 Nm, floating ring gear for thermal expansion, high-viscosity ATF or gear oil. Compact track loaders (CTLs) and compact skid-steer loaders with high-flow auxiliary hydraulic circuits use planetary hub reduction gears integrated directly into the drive wheel hub — a configuration known as a “planetary wheel motor” or “hydrostatic wheel drive.” The planetary gearbox sits between the hydraulic motor output shaft (at 1,000–4,000 RPM) and the wheel hub (at 50–200 RPM), providing the required wheel speed reduction and torque multiplication in the confined space of the wheel. Operating environment: mud, water, tree debris, and occasional submerged operation during stream crossing — the hub planetary seal must prevent all external contamination while retaining gear oil. Korea Ever-Power supplies compact track loader planetary hub gear sets with the same dimensional and material specification as the original equipment, including the floating ring gear feature that allows the ring gear to expand thermally without pre-loading the planet gears.

APP 04

PILING RIG
CROWD DRIVE

Planetary gear specification: M5–M10, 18CrNiMo7-6 carburized, DIN 6–7, single or two-stage planetary, output torque 30,000–120,000 Nm, high service factor 2.0–2.5, high-viscosity oil ISO VG 320, thermal monitoring recommended for continuous operation. Rotary piling rigs use planetary gearboxes in two positions: the rotary drive head (which rotates the Kelly bar and auger for CFA and bored pile drilling, driving the auger through the ground at high torque and low speed) and the crowd drive (which pushes the Kelly bar vertically into the ground against the resistance of the soil). The crowd drive planetary gearbox experiences extremely high continuous torque at very low speed — often below 5 RPM output — requiring high gear ratios and maximum tooth load capacity. Auger drives experience high shock loading when the auger tip encounters boulders or hard rock in the soil profile — these impact events generate torque spikes exceeding 3× the continuous rated torque, necessitating service factor 2.5 in the planet gear design. Korea Ever-Power supplies piling rig planetary gear sets for Bauer, Soilmec, Casagrande, and Liebherr piling equipment crowd and rotary drive gearboxes — contact with the rig model and rated crowd/rotary force for specification and quotation.

OIL SPECIFICATION

• • ISO VG 220: standard for ambient above 0°C
• • ISO VG 150: cold climate below -10°C ambient
• • ISO VG 320: piling rig crowd drives >80°C
• • Synthetic PAO: extended service to 6,000 h
• • GL-5 EP additive: confirmed compatible with all steel planetary gears

OIL CHANGE INTERVALS

• • Initial change: 250–500 hours (running-in particles)
• • Mineral oil: every 2,000–3,000 hours or annually
• • Synthetic PAO: every 4,000–6,000 hours
• • After any suspected water ingress: immediate drain
• • Magnetic drain plug check every oil change

SEAL CONDITION MONITORING

• • Check oil level every 250 hours (loss = seal failure)
• • Inspect lip seal track for groove wear at every oil change
• • Replace all seals at every second oil change as preventive
• • Water contamination test: white emulsion in oil = reseal immediately
• • Seal replacement timing: earlier than failure = lowest total cost

My 20-tonne excavator travel motor is overheating on slopes, and I’ve noticed the oil in the final drive is metallic-coloured. What is likely wrong, and should I replace the planetary gear set?

Metallic oil and travel motor overheating in an excavator final drive is a serious symptom that requires immediate investigation before the machine is returned to duty — continuing to operate with metallic oil contamination will damage the hydraulic travel motor in addition to the final drive gearbox. Diagnosis sequence: (1) Check oil level and colour: drain the final drive oil into a clean container. Silver-grey metallic colour with a fine metallic precipitate indicates planet gear or ring gear surface degradation — this is the most common cause of overheating through increased friction from damaged tooth surfaces. Dark brown or black oil with a cooked smell indicates thermal degradation from sustained overtemperature operation — check for restricted cooling airflow to the gearbox exterior (mud packed around the housing) or incorrect oil viscosity. (2) Check magnetic drain plug: remove the drain plug and inspect for metal particles. Fine grey powder on the magnet is normal background wear; larger flakes (1+ mm) indicate tooth flank pitting or spalling. (3) Operate the machine on level ground and check travel speed: if both tracks still drive at equal speed and the machine can drive without overheating on level ground, the internal gear damage may not yet be severe enough to cause immediate operational failure. (4) Borescope inspection if possible: some excavator final drives have an inspection port; borescope inspection through the oil fill port can reveal the condition of accessible planet gear tooth flanks. If the oil contains large metal flakes and the machine overheats on grade operation, immediate gearbox rebuild is recommended — continued operation risks hydraulic motor damage through contaminated oil from the gearbox entering the hydraulic circuit. Korea Ever-Power can supply a complete replacement planetary gear set for the specific excavator model within 15–25 days depending on the machine class — contact with excavator make, model, year, and serial number for the correct gear set identification.

Can Korea Ever-Power supply planetary gears for Komatsu, Caterpillar, Hitachi, and Doosan excavator travel drives as aftermarket replacement parts?

Korea Ever-Power supplies excavator final drive planetary gear replacement sets for all major excavator brands as aftermarket (non-OEM) replacement parts. Coverage: Komatsu (PC60 through PC800 series), Caterpillar (303 through 395 series), Hitachi (ZX55 through ZX500 series), Doosan (DX55 through DX480 series), Volvo (EC60 through EC750 series), Liebherr (R9 and R9000 series), Hyundai (HX55 through HX520 series). Supply is available in three formats: (1) Gear set only (sun gear, planet gears, and ring gear for specified stage) — the carrier, needle bearings, and seals are reused from the existing gearbox if in good condition. (2) Complete stage kit (gear set + planet carrier + planet shaft needle roller bearings) — everything needed for a stage rebuild without any reused components. (3) Complete final drive rebuild kit (both planetary stages complete + all bearings and seals) — the most comprehensive supply for gearboxes where all internal components have been contaminated by metal debris. All Korea Ever-Power aftermarket excavator planetary gears are manufactured to the same material and dimensional specification as the OEM parts — 18CrNiMo7-6 carburized where the OEM part is carburized steel, same module and tooth count as the original gear. The parts are not OEM branded but are interchangeable with OEM parts in all functional respects.

What is the expected service life of a correctly specified excavator final drive planetary gear set, and what operating factors most reduce this life?

A correctly specified and maintained excavator final drive planetary gear set for a 20T class machine (18CrNiMo7-6 carburized, ISO VG 220 gear oil, 4,000-hour oil change intervals) has a B10 design life of 10,000–15,000 hours — meaning 90% of identically-specified gear sets will achieve this life without tooth fatigue failure under the rated operating cycle load distribution. In practice, the actual service life achieved varies widely based on operating factors: (1) Oil contamination is the single greatest life reducer — water contamination above 0.5% volume eliminates the EHL film and causes micro-pitting that reduces gear life to 20–30% of design. Contamination from breached shaft seals is the primary mechanism. Inspect shaft seals every 250 hours. (2) Machine operating cycle severity — a machine used predominantly in hard rock demolition at full hydraulic pressure (70%+ of operating hours at or above rated torque) will exhaust the tooth bending fatigue life in 6,000–8,000 hours rather than 12,000+; a machine used predominantly in soft soil trenching (average torque 40–50% of rated) may achieve 18,000–20,000 hours. (3) Slope operation percentage — machines that spend more than 30% of operating hours driving on slopes above 20° use the travel motors (and final drives) at sustained high torque well above the level of flat-ground operation. This dramatically accelerates fatigue damage accumulation. (4) Oil change adherence — every missed oil change at the specified interval allows particulate contamination to accumulate in the oil and increases the abrasive wear rate. The first oil change at 250–500 hours is the most important — it removes the fine metal particles from running-in before they can cause three-body abrasive wear damage to the tooth surfaces.

Spur Gears

Forged · high impact · 18CrNiMo7-6

Helical Gears

Double helical · heavy machinery · mill

Engrenages coniques

Right-angle · pump drive · PTO

Worm Gears

Self-locking · stabiliser · auxiliary

Ring Gears

Slewing · excavator swing · large OD

Planetary Gears

Excavator · crane · loader · piling rig

Plastic Gears

MC Nylon · instrument · light drives