EP-SE405.4T Multi-Stage Track Drive Planetary Gearbox

Ang EP-SE405.4T is a multi-stage track drive planetary gearbox for crawler undercarriages in the 40–70 tonne machine class. Its rotating outer housing — carrying the track sprocket directly on the drum flange, without any output shaft or coupling — delivers 11,000 N·m at selectable ratios from i=26 to i=57, driven by a high-speed axial piston motor at up to 3,500 rpm. The integral spring-applied, hydraulically-released multi-disc brake engages automatically on pilot pressure loss. At ~140 kg, EP-SE405.4T is a physically substantial unit — sized for machines where the undercarriage weight alone often exceeds 8 tonnes per side.

At ≥95% efficiency, the EP-SE405.4T loses at most 5% of the transmitted power as heat. For a 100 kW input (typical for a 45-tonne excavator travel circuit), that is at most 5 kW of heat generated in the gearbox housing at rated load — less than the heat output of a domestic electric kettle. Compare this with a single-stage unit at the same power: because single-stage units cannot reach 11,000 N·m in the SE series, the alternative for 40-tonne machines would be two parallel-shaft reducers or a much larger and heavier single-ratio unit. The multi-stage optimised epicyclic achieves more torque multiplication in a shorter axial length, and the gear mesh efficiency is maintained through precision CNC ground helical tooth profiles at each stage.

Drive efficiency directly affects hydraulic fluid temperature: every percentage point of efficiency lost in the gearbox becomes heat in the hydraulic return circuit. At ≥95% efficiency versus a hypothetical 92% alternative, the EP-SE405.4T generates approximately 3 kW less heat per 100 kW transmitted. On a machine with two 100 kW travel circuits running for 8 hours per day, this prevents roughly 172 MJ of accumulated heat from entering the hydraulic system daily. In hot-climate operation — Pilbara or Arabian Peninsula, for example — this difference in fluid temperature directly affects pump and seal life. Multiple field reports across Korea Ever-Power's installed base have documented hydraulic oil temperature reductions when replacing lower-efficiency legacy drives with EP-SE405.4T units.

In diesel-hydraulic machines, every watt of power lost in the drive-train must be supplied by the engine — which converts diesel at approximately 35% thermal efficiency. A 5 kW efficiency improvement in the travel drives therefore reduces diesel consumption by approximately 14 kW of thermal input per drive, per hour of travel operation. For a large excavator spending 4 hours per day on travel cycles, across a 250-day construction season, the fuel saving from two improved drives is measurable and cumulative. At commercial diesel prices and for fleet operators running multiple large machines, the ≥95% efficiency specification is not a marketing claim — it is a recurring cost reduction that compounds over equipment service life.

The EP-SE405.4T weighs approximately 140 kg — 65% heavier than the EP-SE403T2 (85 kg), nearly double the EP-SE402T2 (75 kg), and four times the compact EP-SE400T1 (35 kg). This is not incidental. The relationship between drive unit mass and machine class reflects several connected engineering constraints that cannot be addressed any other way.

Large Crawler Excavators — 35–60 Tonne

The 35–55 tonne crawler excavator class is the primary target application for EP-SE405.4T globally. Machines in this class — used for large-scale trenching, rock breaking on infrastructure projects, and heavy site preparation — require individual track drives capable of 9,000–11,000 N·m after applying shock load factors for hard rock and deep bucket fill. EP-SE405.4T covers this at ratios from i=33 to i=45. The spring brake provides the mandatory positive mechanical hold required by machine safety standards in many markets for excavators above 35 tonnes operating on grades above 15°. At i=40, the spring brake equivalent at the sprocket is 11,200 N·m per drive — sufficient for the machine's parking requirement with an adequate safety margin.

Large Rotary Drilling Rigs — 50–100 Tonne Class

Large rotary drilling rigs — bored pile rigs, continuous flight auger (CFA) rigs, and diaphragm wall grabs in the 50–100 tonne class — require EP-SE405.4T for the undercarriage travel drives. These machines travel slowly (under 1 km/h during repositioning on site), placing them in the high-ratio end of EP-SE405.4T's range (i=45–57). The 11,000 N·m capacity handles the full machine weight including the kelly bar, mast, and counterweight during repositioning across soft or sloped ground. The spring brake provides the automatic position hold between bore moves when the engine may be at idle or the travel circuit inactive during pile cage placement.

Large Mobile Crushers — Heavy Track Drive Demand

Tracked primary jaw crushers and impact crushers above 50 tonnes operating weight require EP-SE405.4T for the undercarriage travel. At this weight class, the combination of machine mass plus jaw crusher vibration loads exceeds the structural capacity of the SE403T2's 85 kg nodular iron housing. EP-SE405.4T's heavier nodular iron construction sustains the continuous vibration without housing micro-fracture. In limestone, granite, and basalt quarries with aggregate dust and fine silica, the floating mechanical face seals prevent the drive oil contamination that destroys rubber-sealed alternative units within hundreds of hours.

Large Crawler Cranes — Undercarriage Travel

Crawler cranes in the 50–100 tonne gross vehicle weight class use EP-SE405.4T for travel drives. At i=50–57 (slowest ratios), the drive provides approximately 14,000–15,960 N·m per side — the tractive force required to move a fully counterweighted crane across typical compacted site ground. The spring brake is critical during lift operations: with a suspended load, the crane tracks must remain absolutely stationary, and the spring brake provides this hold without requiring hydraulic circuit maintenance. Long repositioning moves between lift picks, with the boom elevated and load on the hook, operate at the i=26–35 range for acceptable travel speed.

Heavy Agricultural and Forestry Equipment

At the 40–70 tonne class, tracked forestry machines (large feller bunchers and heavy timber haulers) and large tracked agricultural platforms (big-frame combines, soil sampling platforms) require EP-SE405.4T for travel final drives. In timber harvesting, the impact from dragging heavy log bunches across stumps and root systems creates shock loads that require the full gear set and housing mass of EP-SE405.4T to absorb safely. The downstream agricultural multi-output gearboxes for PTO-driven cutting heads and conveyor drives operate independently from the EP-SE405.4T travel circuits.

Specialised Tracked Platforms — Ports, Mining, Tunnelling

Port segment handlers, tunnel invert handlers, and heavy autonomous tracked mining platforms require EP-SE405.4T for the track drives. In underground mining, the compact axial length of the rotating-housing design fits within restricted tunnel cross-sections that cannot accommodate larger gearbox units. The worm gear reducers serving the platform's auxiliary cable tensioners or horizontal conveyors operate entirely separately from the EP-SE405.4T travel drive circuits — the worm unit provides self-locking hold on the cable drum while the spring brake holds the chassis position.

Ratio + Dimensional Confirmation Same Day

Provide your target travel speed, hydraulic motor specification, machine gross weight, steepest gradient, and incumbent drive model. Korea Ever-Power returns: ratio selection from i=26–57; brake hold adequacy calculation (280 N·m × selected i vs your required holding torque); and explicit dimensional confirmation against your current drive — spindle bore, drum OD, sprocket bolt circle, motor interface — same business day, no charge, no commitment. For urgent machine-down situations, the same-day response applies.

Complete Drive Package — Motor + Valves + Gearbox

EP-SE405.4T is available pre-assembled and function-tested with a matched axial piston motor, integrated overcenter valve, and pressure relief valve as a single part number. The brake function is verified before shipping: pilot pressure applied, drum rotation confirmed free, pressure released, drum confirmed locked. Oil filled to correct level. Arrives ready for chassis mounting and hydraulic line connection only.

Full Spare Parts Stock — 140 kg Unit Serviced, Not Replaced

At 140 kg and proportional cost, a complete unit replacement for a single failed component is economically indefensible. Korea Ever-Power maintains independent stock of all internal wearing items: mechanical face seal kits, taper bearing sets, multi-disc brake packs, sun gear and planet gear assemblies, and housing O-ring sets. Component-level repair is supported — a failed brake pack is resolved with a brake pack kit, not a complete unit order.

12-Month / 18-Month Warranty — Both Stages and Brake

12 months from commissioning or 18 months from shipment, covering all manufacturing and material defects including the multi-stage gear sets and brake assembly. For OEMs stocking units before machine assembly, warranty begins at commissioning — providing the full 12 months of in-service coverage regardless of stock time. Warranty replacement components are dispatched independently from stock.

7–14 Day Stock · 30–45 Day Custom

Standard ratio configurations available from Korea Ever-Power stock in 7–14 days. Custom ratio and pre-assembled motor packages: 30–45 days. For large OEM batch orders where lead time certainty is critical, Korea Ever-Power can confirm production scheduling and batch allocation timelines at enquiry stage. Expedited shipping available on request.

Arctic to Desert — No Special Configuration

Standard EP-SE405.4T operates at −25°C to +90°C with standard GL-5 gear oil — no special configuration required for either climate extreme within this range. Arctic cold-start seal integrity is maintained by the floating metal face seals, whose spring-loaded face contact force is independent of oil viscosity; the GL-5 VG 150 oil at −25°C remains fluid enough for splash lubrication at the gear mesh points from the first rotation. The spring brake Belleville stack retains adequate clamping force at −25°C without preheating. Desert operation at +45°C ambient — with the machine running a full travel duty cycle — maintains housing temperature below the +90°C limit at the ≥95% efficiency level: a 100 kW circuit generating at most 5 kW of heat in the gearbox, dissipated by the nodular iron housing mass and oil circulation. Hydraulic fluid temperature in the travel return circuit is kept lower by this efficiency level — directly extending pump and motor seal life in sustained desert operation.

Running a fleet of 48-tonne autonomous crawler platforms for deep-shaft ore transport in Nevada. Ambient temperature peaks at +48°C; the silica dust from dry ore is sub-20 micron and destroys rubber seals in a matter of weeks. Previous European drives — retired after repeated seal failures at 600–800 hours — were replaced 1:1 with EP-SE405.4T. At 3,200 hours across four units, the floating metal face seals have not been replaced. Hydraulic oil temperatures in the travel circuit are 6–8°C lower than with the old drives, which we attribute to the stated ≥95% efficiency. Spring brake function verified at the annual maintenance: all four brake packs hold within specification. The 140 kg unit weight required proper lifting equipment during installation, but Korea Ever-Power provided the required lifting point specification in the dimensional drawing.

We manufacture large bored-pile drilling rigs in the 70–90 tonne chassis class. At this machine weight, we specify EP-SE405.4T at i=50 for the undercarriage travel drives. The spring brake is a non-negotiable specification in our market — rig operators park on sloped sites with the kelly bar down and engine off during crew breaks, and the spring brake holds the machine stationary without any hydraulic circuit pressurisation. Korea Ever-Power confirmed the 280 N·m × i=50 = 14,000 N·m per drive exceeds our parking hold requirement with a comfortable safety margin. Dimensional confirmation to our legacy GFT drives was provided the same day we submitted the inquiry. We have now transitioned our full production range to EP-SE405.4T for this chassis class — lead times of 7–14 days from stock suit our production schedule well.

We operate heavy timber hauling feller bunchers and heavy pipe-laying tracked machines in Alberta — operating temperatures range from −28°C in winter to +35°C in summer. The previous drives failed at low temperature: brake packs freezing engaged at −25°C, requiring heat application before the machine could travel. EP-SE405.4T brake releases cleanly at −27°C with no pre-warming procedure at our standard 18 bar pilot pressure. Cold-start travel on first movement of the day is smooth at VG 150 oil without a warm-up idle period. In summer, operating in clay and organic soil, the floating face seals have maintained clean oil samples across two full operating seasons — zero water or organic ingress confirmed at each 500-hour oil check. 1:1 swap with legacy drives: chassis unchanged, hydraulic lines unchanged.

QThe spec says ≥95% efficiency. Is this higher than the SE402T2 and SE403T2 which claim >94%? How is that possible at higher torque?

The ≥95% figure for EP-SE405.4T comes directly from the Korea Ever-Power product specification for this model. The lower >94% figure for SE402T2 and SE403T2 reflects the double-stage (T2) layout's per-stage losses. The EP-SE405.4T uses a different multi-stage configuration where the individual stage ratios and gear geometry are optimised for efficiency at this torque class. The specific stage count and layout are manufacturer-internal design details — what matters for engineering purposes is the tested output efficiency figure of ≥95%, which Korea Ever-Power states for this model. If you require independent efficiency verification for a specific application power budget, Korea Ever-Power can provide test data from factory acceptance testing for units produced to your order specification.

QCan a 140 kg unit be installed in the field — or does it require workshop equipment?

EP-SE405.4T field installation requires a rated lifting device: a small electric hoist, chain block rated ≥200 kg, or an excavator auxiliary line with a rated lifting sling. The unit must not be manually lifted by installation technicians. Korea Ever-Power's dimensional drawing specifies the lifting attachment points (chain wrap positions on the drum housing) for safe suspended installation into the chassis bore. The actual installation procedure — aligning the spindle into the chassis bore, setting the motor, connecting hydraulic lines — is performed by two technicians and typically requires 3–5 hours per side. The extra weight compared to SE403T2 extends installation time by approximately one hour per side, primarily due to the controlled lift positioning requirement. Korea Ever-Power provides installation sequence documentation with each unit.

QWhat oil volume does the multi-stage unit require, and does the larger housing change the fill procedure?

The EP-SE405.4T multi-stage housing contains a significantly larger oil volume than the double-stage SE402T2 or SE403T2 — typically 4.5–7.0 litres depending on ratio configuration and motor adapter. The exact fill volume is specified on the Korea Ever-Power dimensional drawing for your specific configuration. Fill procedure is the same as other SE units: through the highest port in the operating orientation; level check at the side port. At this oil volume, the first run-in oil change at 150 hours removes a larger quantity of wear particles from the multi-stage gear mesh than smaller units — ensure adequate drain time (oil warm, drain plug down for at least 15 minutes) before refilling. Change interval thereafter: 1,000 hours or annually.

QWhat maintenance schedule applies to the spring brake disc pack?

The spring brake multi-disc pack in EP-SE405.4T is a wet-bath unit — the brake discs operate in the same GL-5 gear oil that lubricates the planetary gear stages. This means the oil at each scheduled change (150 hours first change, then 1,000 hours or annually) carries away any fine metallic wear particles from the brake disc surfaces, serving as an indirect brake condition monitoring tool. If oil samples at the 1,000-hour change show an elevated metallic particle count disproportionate to the gear mesh baseline, this indicates accelerated brake disc wear and warrants a brake pack inspection. The brake disc pack itself — friction discs, steel separator plates, and the Belleville spring stack — is available as a replacement kit from Korea Ever-Power stock. Replacement is a workshop procedure requiring partial disassembly of the motor-brake interface. Korea Ever-Power provides the brake pack replacement procedure in the service documentation supplied with each unit. Brake function verification (pilot pressure applied → drum free, pressure released → drum locked within one second) should be performed at each annual service interval and after any machine hydraulic system maintenance that involved the pilot circuit.

QIs EP-SE405.4T a true drop-in replacement for Rexroth GFT or Bonfiglioli 700C at 11,000 N·m?

For units in the equivalent 11,000 N·m torque class with matching ratio, EP-SE405.4T is dimensionally matched to Rexroth GFT and Bonfiglioli 700C equivalents at this class. Korea Ever-Power provides an explicit dimensional comparison document — spindle bore, drum OD, sprocket bolt circle, hydraulic port positions, motor interface — against the specific legacy model number before any order commitment. The ratio must match (or be close enough for acceptable performance): both the legacy drive and EP-SE405.4T offer multiple ratio options at this torque class. Provide your incumbent drive model number and current ratio to Korea Ever-Power for same-day cross-reference confirmation. Rexroth and Bonfiglioli are trademarks of their respective owners, cited for reference only.