Rear Axle Assembly Series

EP-EB02 Rear Axle Assembly

Complete Rear Drive Axle Assembly for 3.5 KW Electric Tricycles — Gear Ratio 10.088 • Max Input Torque 22 N·m

2. What Is the EP-EB02 Rear Axle Assembly?

The EP-EB02 is a purpose-built, complete rear axle assembly engineered for 3.5 KW electric tricycles deployed in urban freight, agricultural transport, and last-mile delivery operations. Unlike loose component sets, this rear axle assembly arrives as a single factory-tested unit — integrating the rear axle housing, differential gearbox, drive shafts, wheel hubs, sealed bearings, and oil-bath lubrication system into one compact, installation-ready assembly. The result is a rear drive axle assembly that significantly shortens service time, eliminates the risk of field assembly errors, and delivers predictable performance from day one.

What is the rear axle assembly, technically speaking? It is the structural and mechanical bridge between the drive motor and the rear wheels. In the EP-EB02, torque from the electric motor enters the rear axle gearbox via the internal spline input shaft, passes through a multi-stage gear reduction with a final gear ratio of 10.088, and is distributed to both rear wheel axle shafts through a bevel differential. This arrangement allows smooth cornering without tire scrub while maintaining strong traction under load. The centre-to-centre spacing of 136 mm is matched to the torque envelope of 3.5 KW hub-drive systems common in the commercial tricycle segment across Bahrain, the wider GCC market, and South and Southeast Asian logistics fleets.

For procurement engineers evaluating rear axle assembly replacement options for an existing electric tricycle fleet in Bahrain or planning an OEM sourcing arrangement, the EP-EB02 offers a combination of dimensional accuracy, consistent quality, and straightforward fitment that makes it a strong candidate for both new-build and service-replacement applications. The entire rear end axle assembly weighs 38.5 kg and measures 1302 mm in length, 352 mm in axle track width, and 251 mm in height — dimensions verified against production drawings at every batch.

3. Five Key Product Advantages

4. How the Rear Axle Assembly Works

Understanding the working principle of a rear axle assembly starts at the power input. Rotational energy from the electric motor enters the EP-EB02 rear axle gearbox through the internal spline input shaft at the top of the housing. Inside the compact gear housing, the first stage involves a helical gear pair — chosen for quieter operation compared to straight-cut gears — that begins the speed reduction process. This stage accounts for a substantial portion of the overall 10.088 final ratio, converting high-speed, low-torque motor output into the intermediate shaft speed needed to drive the differential.

The differential assembly is the heart of any rear complete axle assembly. In the EP-EB02, the differential uses a bevel-gear open differential design. The ring gear on the differential carrier meshes with the pinion to complete the final reduction stage. Inside the carrier, two side bevel gears engage with two spider bevel gears mounted on a cross pin. This arrangement is the key to rear axle assembly showing internal parts in its truest engineering sense: it allows the left and right rear drive axle shafts to rotate at different speeds when the vehicle corners, while still summing torque equally to both wheels when traveling straight. During straight-line driving, spider gears do not rotate relative to the carrier; during cornering, they rotate to compensate for the speed difference between inner and outer wheels.

The axle shafts extend outward from the differential to the wheel hub flanges. Each shaft is supported by a tapered roller bearing at the wheel end and a sealed ball bearing at the differential end. These bearings handle both radial loads from the vehicle weight and axial thrust loads generated during cornering. The rear axle housing — the structural spine of the entire assembly — is a hollow beam that houses the axle shafts, encloses the differential in its central section, and provides the mounting points for the brake plates, wheel hubs, and vehicle frame brackets.

Lubrication throughout the rear wheel axle assembly is passive splash lubrication. The differential crown gear scoops gear oil from the sump as it rotates, distributing it to gears, bearings, and the axle shaft oil seals. This self-contained approach means no external pump, no electrical lubrication system, and minimal maintenance — simply a periodic gear oil check and replacement according to the service interval.

5. Materials & Construction Quality

Every material selection in the EP-EB02 rear axle assembly reflects decisions made at the engineering stage to balance strength, weight, machinability, and long-term durability. The rear axle housing — the load-bearing spine of the entire rear end axle assembly — is cast from ductile iron (QT450-10), a grade that offers significantly higher elongation and impact resistance compared to standard grey cast iron. This matters in commercial tricycle applications where the axle housing must absorb road shock and torsional loads repeatedly over hundreds of thousands of operational cycles without cracking or deforming. The housing undergoes CNC precision machining on all bearing seats and mounting faces, held to H7 tolerance class for bearing interference fits.

The axle shafts are forged from 40Cr chromium-alloy steel, heat-treated to achieve a core tensile strength of approximately 900 MPa with a surface hardness of 55–60 HRC on the spline engagement zone. This dual-property profile — tough core, hard surface — is the engineering ideal for rear wheel axle shafts that must resist bending fatigue while withstanding spline wear from repeated torque loading. Gears within the rear axle gearbox are cut from 20CrMnTi carburizing-grade steel, case-hardened to 58–62 HRC. All gear teeth are finish-ground to achieve a surface roughness of Ra 0.8 or better, directly contributing to quiet operation and reduced heat generation under load.

Bearings throughout the rear differential axle assembly are sourced from certified bearing suppliers meeting ISO 3290 grade requirements. Oil seals are NBR (nitrile rubber) lip-type seals with a stainless steel spring, rated for continuous operating temperatures compatible with the EP-EB02’s full operating temperature range. All fasteners are grade 8.8 or higher, zinc-phosphate treated for corrosion protection. The gear oil fill and drain plugs are magnetic, capturing metallic wear particles during normal operation as an additional reliability measure.

6. Application Scenarios

7. Regulatory & Compliance Considerations

Sourcing a rear axle assembly for electric tricycles across international markets requires awareness of the regulatory frameworks governing drivetrain components, vehicle safety, and gear transmission equipment. Below is a summary of relevant standards and regulations that buyers in Bahrain and other regions should consider when evaluating rear axle assembly parts for procurement.

Bahrain & GCC: The Kingdom of Bahrain follows GCC Standardization Organization (GSO) technical regulations, which align closely with international ISO and IEC standards for vehicle components. Electric tricycles operating as commercial delivery vehicles in Bahrain may require compliance with GSO 1882 (motor vehicle lighting and signalling) and relevant Gulf vehicle type-approval regulations. Drivetrain and rear axle components themselves do not require individual product certification under current GSO frameworks, but vehicles must meet aggregate roadworthiness standards under Bahraini Traffic Law No. 19 of 2001 and its subsequent amendments.

Avrupa Birliği: For buyers in EU member states, Regulation (EU) 168/2013 governs the approval of L-category vehicles (including three-wheelers). Rear axle assembly components used in EU-registered vehicles must not impair compliance with the vehicle’s type-approval certificate. Manufacturers supplying OEM rear axle assemblies to EU tricycle producers should ensure dimensional and performance specifications are documented to support the vehicle approval process.

India: India’s Central Motor Vehicles Rules (CMVR) and AIS standards apply to electric three-wheelers. AIS-038 Rev.2 covers construction and approval of electric vehicles, and AIS-004 addresses performance requirements. Rear axle gearbox components used in AIS-certified vehicles should meet the torque and dimensional requirements referenced in vehicle-level approvals. BIS (Bureau of Indian Standards) also issues standards relevant to gear assemblies under IS 2535 and related specifications.

ISO Standards: Internationally, ISO 6336 governs the calculation of load capacity for spur and helical gears, and ISO 1328 defines gear accuracy grades. These standards form the engineering basis against which rear axle gearbox gear sets in the EP-EB02 are designed and quality-controlled. Buyers requiring traceable quality documentation can request test reports referencing these standards.

8. About Us

We are a specialized high-technology manufacturer focused on the design, development, and production of electric vehicle reduction gearboxes and complete ATV/UTV front and rear axle transmission assemblies. The production capability covers over 20 product series and more than 100 model variants, with a combined annual output capacity exceeding 300,000 units across all product lines.

Quality management is anchored by IATF 16949:2016 certification — the automotive industry’s most demanding quality standard. This is complemented by ISO 9001:2015 system controls, national fire torch plan industrialization certification, and work safety standardization certification. The in-house quality laboratory operates Coordinate Measuring Machines (CMM), gear measurement centers, comprehensive gearbox test benches, metallographic microscopes, holographic imaging systems, and intelligent performance testing equipment. Every rear axle assembly batch is subject to a multi-stage quality gate process from raw material incoming inspection through final performance verification.

The R&D team brings seven core engineering capabilities: design, analysis (including CAE/FEA), prototype fabrication, validation testing, drivetrain NVH performance development, engineering documentation, and production ramp support. Multiple national utility model and design patents protect key innovations in differential and gear assembly design. As a strategic supplier to numerous major vehicle OEMs and a recognized vendor in the international ATV/UTV aftermarket, the operation combines the process discipline of an automotive Tier 1 supplier with the product depth of a specialist transmission manufacturer.

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9. Related Products & System Compatibility

A complete drivetrain solution goes beyond the rear axle assembly itself. We supply the full range of mating and ancillary components needed for a one-stop procurement experience, ensuring dimensional compatibility across all parts within the drivetrain system.

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