A travel motor is really two machines sharing one shaft: a hydraulic motor on one side and a gear reduction on the other, with seals deciding which oil stays where. When a leak appears, the first question is not "how much oil" but "which oil, coming from where" — because each leak path points at a different seal, a different repair cost and a different level of urgency.
Leak one: oil mist on the track frame
The floating seal between the hub and the track frame keeps the gearbox oil in and the dirt out. When it starts to go, you see a fine oil mist sprayed on the inside of the track frame, collecting dust into a greasy collar. Catch it here and the repair is a seal kit and clean oil. Ignore it and the same leak runs in reverse — grit and water enter the gearbox, and the gears and bearings follow the seal into the parts order. The floating seal is the cheapest seal on the machine relative to what it protects.
Leak two: gearbox oil level dropping with no visible leak
When the gearbox loses oil but the frame stays clean, the oil is going somewhere you cannot see — past the shaft seal into the hydraulic motor side. The tell-tale is at the motor case drain: crack the drain plug after the machine has stood overnight and watch what comes out. A case drain should give a trickle of hydraulic oil; a flood of gear-oil-smelling fluid means the shaft seal between gearbox and motor has failed. This one is urgent — the gearbox is slowly emptying itself into the hydraulic circuit, and the motor side is running on the wrong oil.
Leak three: hydraulic oil from the motor body
External hydraulic leaks — at fittings, at the cover, at the brake line — are the least mysterious but still deserve care. Clean the motor, run it, and watch. What matters is not the drip but whether the leak changes with travel direction or with the brake release, because that tells you which circuit is actually losing oil. A leak that only appears under travel load can be a crack that opens with pressure, not a fitting at all.
One habit that prevents most of this
Check gearbox oil level monthly, and write the level down. A travel gearbox holds a small volume; by the time a level drop is obvious from the filler plug, the seal has been failing for weeks. The fleets that never buy gear sets are the ones whose logs show a level drifting before the mist appears. And when you do open the gearbox, look at the magnetic plug — a thin fur of normal wear is fine; chunks are a sentence, not a warning.
Ordering the right repair
Travel motor identity decides the seal kit, so get the numbers before you order. On the SK200-8 and SK210-8 the travel motor is the Nabtesco GM38VB family, commonly quoted as YN15V00037F1 / F2 / F3; larger machines carry the GM85VA family, quoted as LS15V00020F1. Send the motor nameplate, the machine model and serial number, and photographs of the leak area, and we will quote the seal kit — or the exchange unit, if the damage is already inside — within 24 hours, with the grade of every line stated. Email kobelco-parts@foxmail.com or WhatsApp +86-18144825432.
Guangzhou Shenyue Machinery Technology Co., Ltd. is an independent supplier of Kobelco parts — not an authorized Kobelco dealer — and an authorized distributor for Mitsubishi, Garrett, TONGMYUNG, Marusan and NIKURA. We hold 3,000+ part types in stock and 100,000+ part numbers available to order.