EP-9.311 Rotary Cultivator Gearbox – 50HP, 1:3 Ratio, Standalone Unit
★ The Mid-Range Workhorse — EP-9.311 Standalone Gearbox for the 40–55HP Compact Tractor, When You Already Have the Shaft
The EP-9.311 is the gearbox unit of Korea Ever-Power’s 50HP rotary cultivator drive system — supplied standalone, without the integrated PTO drive shaft that comes with the EP-9.311-JCG kit. At 1:3 ratio, Module 4.35, 36/12 teeth, 540RPM, 21kg in GGG50 nodular cast iron, it is the correct specification for repair and replacement situations where the existing PTO drive shaft is confirmed serviceable and only the gearbox needs changing. The 1 3/8″ Z5 five-tooth spline input — distinct from the six-tooth Z6 used on the EP-75, EP-9.310, and EP-9.312 — is a critical compatibility detail that must be verified against your existing drive shaft before ordering. Bilateral optic axis output connects directly to standard 40–55HP cultivator rotor tube diameters across Korean and Japanese mid-size farm cultivators. Korea Ever-Power supplies the EP-9.311 to agricultural machinery workshops, cultivator OEM manufacturers, and direct farm operators across South Korea, Japan, and Southeast Asia.
EP-9.311 or EP-9.311-JCG? — Start Here Before You Order
EP-9.311 · 50HP · 1:3 · 21kg · gearbox unit only
Korea Ever-Power supplies the EP-9.311 gearbox in two configurations: the standalone unit (this product) and the EP-9.311-JCG complete assembly kit, which includes the gearbox plus a factory-matched PTO drive shaft in any of 14 standard lengths. The internal gearbox mechanism is identical between the two products. The choice comes down to your specific situation:
Choose EP-9.311 (this page) when:
- → Your existing cultivator's PTO drive shaft is still serviceable — confirmed by inspection, not assumption
- → You are replacing only the gearbox on an established machine, not rebuilding the entire drive system
- → Your workshop stocks or can source compatible PTO shafts independently
- → Lower unit cost is the priority
Choose EP-9.311-JCG when:
- → Both the gearbox and shaft need replacing, or you are building a new cultivator assembly
- → You want factory-matched shaft length (14 options: L=375–1,500mm) and assembly-tested joint angles
- → You are an OEM manufacturer wanting one part number for the complete drive system
- → Eliminating shaft length compatibility risk is more important than unit cost
If you are uncertain which to choose, the safest starting point is to physically inspect your existing PTO drive shaft: check for shaft tube damage, cross-joint needle bearing play, safety guard integrity, and spline wear at both ends. If any of these show significant wear, order the EP-9.311-JCG kit. If the shaft is genuinely serviceable and only the gearbox has failed, the EP-9.311 standalone is the correct and more economical choice.
Replacement reference: The EP-9.311 is engineered to match specifications of comparable Bondioli & Pavesi, Comer Industries, and Brevini rotary cultivator gearboxes in the 50HP / 1:3 / M4.35 class. Korea Ever-Power is not affiliated with these brands. References are for specification matching only.
Technical Specifications
The EP-9.311 uses a 36/12-tooth bevel gear set at Module 4.35 — a module value calculated specifically for the 1:3 ratio at 50HP rather than selected from a standard module series. The 36/12 tooth count produces a true 3:1 reduction (36 ÷ 12 = 3, exactly) with no common factors above 1, ensuring all 36 crown gear teeth contact all 12 pinion teeth in a rotating sequence that distributes wear evenly across every tooth face. At Module 4.35, the tooth pitch is approximately 13.7mm — optimised for the combination of 50HP load capacity and 21kg total unit weight.
| Parameter | Value | Notes |
|---|---|---|
| Model | EP-9.311 | Standalone gearbox — no PTO shaft included |
| Speed Ratio | 1 : 3 (fixed) | Rotor turns at 1/3 of PTO input speed |
| Teeth Count | 36 / 12 | Crown gear / Pinion — no common factors, even tooth load distribution |
| Gear Module | 4.35 | Purpose-calculated for 1:3 at 50HP — not a standard series value |
| Rated Power | 50 HP | ≈ 37.3 kW continuous duty |
| Rated Input Speed | 540 RPM | Standard agricultural tractor PTO speed |
| Rotor Output RPM | ≈ 180 RPM | At rated 540RPM PTO input |
| Input Shaft | 1 3/8″ Z5 spline | Five-tooth spline — not Z6. Verify your PTO shaft spline count before ordering. See Section 3 for full explanation. |
| Output Shaft | Optic axis (bilateral) | Plain round output shaft, accessible both sides — connects to standard cultivator rotor tube |
| Housing Material | Nodular cast iron GGG50 | High toughness, impact-resistant, vibration-damping |
| Net Weight | 21 kg | Gearbox only — PTO shaft not included |
Housing dimensions: approx. 162mm × 81mm (from engineering drawing)
The engineering drawing confirms the EP-9.311's compact footprint: approximately 162mm across the wider housing dimension and 81mm depth — notably more compact than the EP-75 (223mm × 202mm) despite the same 1:3 ratio. This compactness is the direct result of the M4.35 module used at 50HP, which allows the 36-tooth crown gear to fit within a smaller pitch diameter than the M6.0 gear used in the EP-75 at its 1:3 configuration. The bilateral optic axis output is visible in the drawing as the through-shaft arrangement — the output shaft passes completely through the housing, allowing the cultivator rotor tube to engage from either side without a separate coupling adapter.
The 38.1mm dimension shown in the engineering drawing corresponds to the input shaft centreline offset from the housing mounting face — a dimension relevant when confirming that the EP-9.311 physically clears the cultivator frame and tractor hitch components in the mounted position. The 155mm dimension represents the overall assembled length including the output shaft extensions. If your existing gearbox's corresponding dimensions differ significantly from these, contact Korea Ever-Power before ordering — dimensional variations between catalogue series from different manufacturers are common in the 50HP tiller gearbox category.
Z5 vs Z6 — The Input Spline Difference You Must Verify Before Ordering
The EP-9.311 uses a 1 3/8″ Z5 (five-tooth) spline at its input shaft. This is the single most important compatibility check for any buyer considering this gearbox as a replacement for an existing unit. The Z5 and Z6 designations refer to the number of spline teeth on the shaft, and they are not interchangeable — a five-tooth spline shaft will not engage correctly in a six-tooth socket, and vice versa, even though both have the same nominal 1 3/8″ shaft diameter.
How to verify your existing spline count:
1. With the machine stopped and PTO fully disengaged, remove the PTO drive shaft from the cultivator gearbox input. 2. Look at the male spline end of the shaft that connects to the gearbox — count the number of spline teeth (raised ridges) around the circumference. 3. If you count five teeth, your shaft is Z5 and will connect to the EP-9.311. If you count six teeth, your shaft is Z6 and is not compatible — you would need a Z6-to-Z5 adapter, or consider whether replacing both gearbox and shaft with the EP-9.311-JCG kit (which supplies a matched Z5 shaft) is the more practical solution. Contact Korea Ever-Power with your spline count result if uncertain — we will confirm compatibility before you order.
The EP Rotary Cultivator Series — Where EP-9.311 Fits
The EP-9.311 occupies the 50HP tier of Korea Ever-Power's rotary cultivator gearbox range — above the 30HP compact-tractor models and below the 62HP upper-mid-range unit. Understanding where it sits helps confirm it is the correct specification for your tractor's actual PTO output:
| Model | HP | Ratio | Module | Input Spline | Weight | Tractor Class |
|---|---|---|---|---|---|---|
| EP-30 / EP-9.310 | 30 | 1:3 | 3.45 | Z6 | 13.5–18 kg | Compact 25–35HP tractors |
| EP-9.311 ← this product | 50 | 1:3 | 4.35 | Z5 | 21 kg | 40–55HP utility tractors |
| EP-9.312 | 62 | 1:3 | 4.58 | Z6 | 27 kg | 55–65HP utility tractors |
| EP-75 | 75–125 | 1:3 to 1:1.6 | 6.0–7.5 | Z6 | 37 kg | 75–125HP large utility tractors |
Note: the EP-9.311 and EP-9.311-JCG are the only models in the EP cultivator series that use a Z5 (five-tooth) input spline. All other models — EP-9.310, EP-9.312, EP-75 — use Z6. If you are replacing a gearbox that was previously fitted with a Z6 input, you need the EP-9.312 (62HP) or EP-9.310 (30HP) rather than the EP-9.311.
Construction Quality — 50HP Sustained Tilling Duty
M4.35 — Purpose-Calculated Module
The M4.35 gear module is not from a standard module series — it is the calculated optimum for the 1:3 ratio at 50HP. The 36/12 tooth count at M4.35 produces a crown gear pitch diameter of approximately 157mm, which fits within the compact 162mm housing width while providing sufficient tooth cross-section bending strength for the torque generated at 50HP and 540RPM. A standard M4.0 module would underspec the bending strength; a standard M4.5 would exceed the housing dimensions. M4.35 is the correct value, not a rounding of either.
GGG50 Nodular Iron — Tine-Impact Rated
In rotary tiller service, the gearbox housing absorbs shock loads transmitted back through the rotor shaft when tines contact buried stones, hard-pan layers, and root masses. GGG50's elongation-at-break of 18% (versus grey iron's <1%) gives the housing the micro-deformation capacity to absorb these events without fracture. For mid-size farm operations in Korea's Chungbuk and Gyeongbuk rocky upland areas — where stone strikes are a routine occurrence in spring tillage — this material property is a genuine service life factor.
Carburised Gears to HRC 58–62
Both bevel gears are carburised to 0.8–1.2mm case depth and quench-hardened to HRC 58–62 — the same specification used throughout the EP series from the EP-RC31 through the EP-40002. At 1:3 ratio, the crown gear carries the majority of the torque load and turns at 180RPM while the pinion turns at 540RPM. The hardened tooth surfaces resist the micro-pitting that develops at the higher contact frequency end (pinion) and the higher tooth loading end (crown) simultaneously.
Dual-Lip Soil-Resistant Output Seals
The bilateral optic axis output shaft exits are sealed with dual-lip NBR seals — the primary lip retains gear oil, the secondary lip excludes soil, crop residue, and water from the bearing cavity. Rotary tiller gearboxes operate with the output shaft directly exposed to the fine soil and crop residue that is most corrosive to bearing lubricant. The dual-lip design maintains seal effectiveness even as the shaft develops the slight lateral movement typical of worn rotor tube bearings after extended field hours.
Bilateral Output Shaft
The optic axis output passes through both sides of the housing, allowing the cultivator rotor tube to engage from either left or right depending on how the implement frame positions the gearbox. This bilateral access eliminates the need for a separate output adapter when replacing a gearbox that was originally mounted with a specific output-side orientation — the same unit accommodates both without modification.
100% Load Test at 50HP
Every EP-9.311 is bench-tested at full 50HP rated load before dispatch — the gear mesh contact pattern under load, bearing temperature, oil seal integrity, and output shaft runout are all verified under operating conditions. Units that pass ship; units that do not are rebuilt. This is the standard across the entire EP series, including the standalone EP-9.311 where the absence of an integrated shaft makes the test faster but equally rigorous on the gearbox mechanism itself.
Where the EP-9.311 Is Used — 40–55HP Farm Cultivator Applications
🌾 Mid-Scale Vegetable Farm Cultivation — Korean Inland Provinces
The 40–55HP utility tractor segment — Daedong CK series, LS XR series, TYM T403 — is the most common tractor class in Korean mid-scale vegetable farm operations across Chungnam, Gyeongbuk, and North Jeolla. These tractors typically mount 1.2–1.5m rotary tillers for spring field preparation of garlic, onion, pepper, and potato fields. The EP-9.311's 50HP rating and 1:3 ratio match the tillage requirements of these operations precisely: sufficient torque for 150–180mm depth in loam-clay soils, and a 180RPM rotor speed that balances tine-soil engagement time against forward travel speed at standard Korean farm tillage rates of 3–5 km/h. Repair workshops serving these areas stock the EP-9.311 as a standard replacement item, particularly for the spring season rush when gearbox failures create time-critical repair demands.
🍅 Protected Cultivation Bed Preparation — Korea & Japan
Greenhouse and polytunnel vegetable production in Korean and Japanese agricultural areas requires thorough soil preparation between crop cycles — breaking up compacted subsoil from pedestrian traffic, incorporating crop residue and organic amendments, and creating the well-structured beds needed for root vegetable production. Compact cultivators in the 1.0–1.2m range, driven by 40–55HP compact tractors, are used for this work in the larger protected cultivation facilities. The EP-9.311 at 50HP handles the moderate soil depth requirements of bed preparation (typically 120–150mm) while its compact 21kg housing fits the weight-constrained mounting designs of cultivators intended for covered-area use.
🔧 Workshop Replacement — Repair vs. New-Build Decision
The EP-9.311 standalone gearbox is the workhorse of the agricultural machinery workshop replacement business in South Korea and Japan. When a cultivator gearbox fails — typically detected by abnormal noise, oil leakage from the output shaft seal, or complete loss of rotor drive — the repair workshop's first decision is whether to replace the gearbox alone or the complete drive system. For machines where the PTO shaft is in good condition (confirmed by checking cross-joint play, tube straightness, and spline engagement at both ends), the standalone EP-9.311 at lower unit cost is the economically correct choice. Korea Ever-Power's 3–5 day delivery to Korean workshops means the machine is back in service within one working week — critical during the narrow spring planting windows that Korean farmers work within.
🌏 Southeast Asian Smallholder Cultivation — Vietnam, Thailand & Philippines
Vietnamese coffee and vegetable highland farms, Thai upland crop operations, and Philippine lowland rice-corn rotation farms increasingly use 40–50HP tractors with compact rotary tillers for mechanised soil preparation. The EP-9.311's 50HP rating covers this tractor class, and Korea Ever-Power's 5–7 day delivery to major Southeast Asian agricultural regions makes it a practical replacement option when the existing cultivator's gearbox has failed and the operator cannot wait 4–6 weeks for an OEM part to arrive from Europe or Japan.
Installation & Maintenance — EP-9.311 Standalone
When fitting the EP-9.311 as a replacement, several installation steps differ from new-build assembly because of the Z5 spline compatibility check and the need to verify the existing PTO shaft condition:
1.Spline count before fitting: Before bolting the EP-9.311 to the cultivator frame, confirm the PTO drive shaft's gearbox-end is Z5 by counting the spline teeth. Do not rely on the previous gearbox's designation — if the previous unit was a non-original replacement, it may have used a different spline standard.
2.PTO shaft inspection before reuse: With the gearbox removed, run the PTO shaft through its full movement range and check: (a) cross-joint play — >2mm of rocking at the joint indicates bearing wear; (b) tube straightness — sight along the tube for bending; (c) safety guard integrity; (d) spline wear at both ends. Any of these failing means the shaft should be replaced alongside the gearbox.
3.Oil fill before first use: The EP-9.311 is dispatched without oil — fill to the level plug centre mark with SAE 90 GL-4 gear oil (approximately 350–400ml) before operating. Running dry even for a few minutes causes immediate bearing and gear surface damage that is not covered under warranty.
4.Break-in oil change at 50 hours: The first 50 hours produce metal particles from gear tooth micro-surface burnishing. Drain and replace the oil at 50 hours to remove these particles. Subsequent changes every 200 hours, or every season — whichever comes first.
✔Annual inspection: At each season's start, check the output shaft end-play by pushing and pulling the shaft axially by hand — more than 0.3mm of movement indicates bearing preload loss requiring attention. Check both oil seals for weeping and the housing exterior for hairline cracks at the bearing seat areas.
Why Agricultural Workshops Choose Korea Ever-Power for EP-9.311
M4.35 bevel gear set production — CNC hobbing and heat treatment
Korea Ever-Power Agricultural Machinery Co., Ltd. produces the EP-9.311 on the same CNC gear hobbing and carburising lines as the EP-75 and EP-9.312 — the M4.35 gear set is a precision-machined component, not a near-specification standard gear. The Z5 input spline socket is machined to the specific geometry that mates with the Z5 PTO shaft used in this gearbox class, and is verified for engagement fit before the housing is assembled.
For Korean and Japanese agricultural workshops that stock common replacement gearboxes for the spring season, the EP-9.311 offers 3–5 business day delivery to maintain the workshop's repair schedule. Single-unit orders are accepted with the same priority and documentation as OEM batch orders — no minimum quantity means repair workshops can replenish stock one unit at a time based on actual usage rather than having to carry large pre-season inventory.
Related Products — EP Rotary Cultivator Range
What Customers Say About the EP-9.311
Frequently Asked Questions — EP-9.311
Additional information
| Editor | Cxm |
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