Transmission Gear

1. Manufactured according to the original vehicle dimensions, enabling perfect replacement of original parts.

2. 12-month quality guarantee service from the date of customer receipt.

3. Small-batch orders are acceptable (retail orders excluded).

4. Focusing on Japanese and Korean models, including Toyota, Mazda, Isuzu, Mitsubishi, Hyundai, Kia, etc.

5. Customizable packaging

I. Constant Mesh Gear Sets

• Type: Helical Gears

• Application Scenario: All forward gears (1st gear to top gear).

• Working Principle: In a manual transmission, except for reverse, all forward gear pairs are in a state of "constant mesh" while the vehicle is moving. This means the gears on the shafts are always rotating, but they do not transmit power to the output shaft until the driver engages that specific gear.

Why Helical Gears?

• Quiet Operation: Helical gear teeth are cut at an angle. Engagement occurs gradually (sliding from one end of the tooth to the other) rather than the instantaneous full-face impact seen in spur gears. This significantly reduces noise and vibration during meshing, ensuring cabin quietness.

• High Load Capacity: Helical gears have a higher contact ratio, meaning more teeth are engaged simultaneously to share the load. This allows them to withstand higher torque, suitable for modern high-torque engines.

• Smooth Operation: Reduced shock loads extend gear life.

II. Shifting Engagement Mechanism

• Type: Dog Teeth / Synchronizer Sleeves (Functionally similar to spur engagement)

• Application Scenario: Used to lock a freewheeling gear to the output shaft to transmit power.

• Working Principle: Although the main gears are helical and constantly meshing, power transmission is achieved via the Synchronizer. The synchronizer consists of a sleeve with internal splines and dog teeth (block-like protrusions similar to straight teeth) on the side of the gear.

• The driver moves the shift lever.

• The synchronizer first uses friction cones to match the speed of the gear with the shaft speed.

• The sleeve slides forward, and its internal straight grooves engage with the dog teeth on the gear.

• The gear is rigidly locked to the shaft, and power transmission begins.

Why Dog Teeth/Straight Engagement Here?

• Compact Axial Space: The dog tooth structure is very compact and does not require the long axial engagement length needed for helical gears.

• No Axial Thrust: Helical meshing generates axial thrust forces that must be absorbed by bearings. Dog engagement primarily handles radial shear forces and generates no additional axial thrust, simplifying bearing design.

• Non-Continuous Relative Motion: Since these teeth only engage momentarily during shifting and then remain locked (rotating at exactly the same speed), they do not undergo the high-speed relative sliding process that requires the smooth transition of helical gears. The rigidity and simplicity of straight-cut engagement are superior here.

III. Reverse Gear

• Type: Spur Gears

• Application Scenario: Reverse gear.

• Working Principle: In most traditional manual transmissions, the reverse gear is achieved by inserting an Idler Gear between two constant mesh gears. This idler is typically a spur gear.

Why Spur Gears?

• Cost and Simplicity: Reverse gear is used infrequently and typically does not need to sustain the same continuous high loads as forward gears. Spur gears are cheaper to manufacture and have a simpler structure.

• Ease of Axial Sliding: In many older or economy transmissions, the reverse gear slides axially along the shaft to mesh with the idler. Spur gears are easier to engage via this axial sliding motion (though modern cars increasingly use synchronizers for reverse as well).

• Noise Characteristic: Spur gears generate significant noise during meshing (the typical "whirring" or grinding sound). In reverse, this noise inadvertently serves as a warning signal, alerting pedestrians and other vehicles that the car is backing up.
  Note: Modern high-end manual transmissions are beginning to use helical gears with synchronizers for reverse to eliminate noise and prevent grinding, but the spur gear idler solution remains common in commercial vehicles and economy cars.

• Standard Material: High-quality case-hardening alloy steels are the industry standard.

Common Grades:

• SAE/AISI: 8620, 9310, 4320, 4140.

• DIN/EN: 18CrNiMo7-6 (1.6587), 20MnCr5 (1.7147).

• JIS: SCM420, SNCM220.

• Key Properties: High core toughness to withstand shock loads and a hard surface to resist wear and pitting.

Heat Treatment:

• Process: Carburizing or Carbonitriding followed by quenching and tempering.

• Surface Hardness: Typically 58 – 64 HRC (Rockwell C) to ensure wear resistance.

• Core Hardness: Typically 30 – 45 HRC to maintain ductility and prevent brittle fracture under impact.

• Case Depth: Critical parameter, usually 0.6 – 1.2 mm (effective case depth), depending on gear module and load.

In the highly competitive automotive after-sales market, the core competitiveness of our shift lever lies in the combination of professionalization and flexibility: we focus on the segmented track of Japanese and Korean vehicle models, and achieve higher product matching accuracy through in-depth research on the characteristics of the brand's transmission system; at the same time, we break the limitation of large minimum order quantity of traditional auto parts manufacturers, support small-batch orders, and provide customizable packaging and perfect warranty service.

Whether you are a repair shop pursuing installation efficiency, a distributor focusing on market demand, or a modification workshop paying attention to product quality, our shift lever can meet your personalized needs with OEM-level quality, flexible procurement terms and targeted after-sales support. We are committed to becoming the most reliable supplier of shift levers for Japanese and Korean vehicle models in the automotive aftermarket!