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Brand: C.OEFT
OE numbers: 81-40
Product Name: Transmission Assembly
Compatible model:81-40
Product status: NEW
Product weight：120KG
Packaging size: 100*100*100cm
Product packaging: Neutral Packaging
Car Series: Chinese
Car Type: For Changan
1. Core Four-Speed Transmission and Torque Conversion
As a four-speed automatic transmission, the 81-40 assembly provides optimized gear ratios to balance power and fuel efficiency. Its transmission ratio range (0.697-2.875) covers all driving scenarios: 1st gear (2.875:1) amplifies engine torque for smooth starts with a full load; 2nd gear (1.568:1) ensures strong acceleration during overtaking; 3rd gear (1.000:1) maintains balanced performance at city speeds; and 4th gear (0.697:1) reduces engine speed to 2200 rpm at 120 km/h, lowering fuel consumption . The hydraulic torque converter with a 216 mm diameter softens engine power input, protecting the powertrain from impact during cold starts. For example, in a 1.4L Chevrolet Aveo, the assembly transmits 123 N·m of engine torque through 1st gear, generating sufficient driving force for uphill climbs with two passengers.
2. Intelligent Downhill Braking and Fault Protection
The TCM of the 81-40 assembly integrates adaptive driving condition recognition, including a dedicated downhill mode . When the system detects increasing acceleration with the throttle fully released (indicating downhill driving), it automatically downshifts from 4th to 3rd gear, utilizing engine braking to control vehicle speed and reduce brake wear. The comprehensive fault diagnosis system monitors 12 key parameters in real time, including oil temperature, solenoid status, and gear position . If a solenoid failure occurs, the TCM immediately cuts power to the affected component and illuminates the malfunction indicator light, while switching to "limp mode" (maintaining 3rd gear and reverse) to ensure safe vehicle retrieval . Common fault codes (e.g., P0750 for S1 solenoid failure) can be quickly read via OBD interfaces, reducing maintenance diagnosis time by 50%.
1. High-Torque Resistant Structural System
The 025CHC15000BK transmission assembly adopts a reinforced gear-train design, with core components including precision-machined helical gears, hardened input/output shafts, and a one-piece cast aluminum alloy casing. The main transmission gears are crafted from high-grade 20CrMnTiH alloy steel, which undergoes carburizing quenching (at 920-940°C) and low-temperature tempering (at 180-200°C) to achieve a surface hardness of HRC 58-62 and a core toughness of ≥1200 MPa . This material optimization enables the assembly to withstand continuous torque loads of up to 380 N·m, with short-term overload capacity reaching 500 N·m—making it ideal for mid-size SUVs and light commercial vehicles equipped with 2.0L turbocharged engines. The helical gear design enhances meshing contact area by 40% compared to straight-cut gears, effectively distributing stress and reducing fatigue failure risks during frequent heavy-load operation.
2. Ultra-High Transmission Efficiency for Fuel Economy
Targeting the energy loss challenge in transmission systems , the 025CHC15000BK integrates multi-stage efficiency optimization technologies. The gear meshing surfaces are precision ground to a surface roughness (Ra) of ≤0.4 μm, and coated with molybdenum disulfide (MoS₂) solid lubricant, reducing meshing friction by 35%. The assembly adopts a low-viscosity fully synthetic transmission fluid (operating viscosity of 7.5 cSt at 100°C) and a high-efficiency oil pump, minimizing churning losses by 20%. These optimizations result in an overall transmission efficiency of 91-94% in the main working range—surpassing traditional AT transmissions (75-85%) and approaching the efficiency level of premium DCT systems . For a vehicle with a 2.0L engine, this efficiency improvement translates to a 6-8% reduction in WLTC comprehensive fuel consumption, equivalent to saving 0.4-0.6 L per 100 km .
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