The shift fork moves the synchronizer sleeve along the gearbox shaft to engage each gear. It must hold tight parallelism and perpendicularity between its fork opening and hub bore, carry a carburized wear surface at the fork pads, and survive millions of shift cycles without deformation. Dimensional precision at the fork opening directly controls shift feel and synchronizer life—making the shift fork one of the most demanding cast components in the transmission.
Ningbo Ruican manufactures gearbox shift forks by silica sol investment casting in AISI 8620 case-hardening steel (DIN 16MnCr5 equivalent), followed by precision CNC machining of the hub bore, fork pads, and detent features. The investment casting process holds the fork opening near net shape, minimizing machining allowance and preserving uniform case depth after carburizing.
Heat treatment is executed to customer specification—typically carburize and quench to a case hardness of 58–62 HRC with a toughened core—and every batch is verified with hardness traverse samples. For manual transmissions, dual-clutch gearboxes, and transfer cases across passenger car, LCV, and off-highway applications, we support programs from prototype (as few as 10 pieces) to annual volumes in the hundreds of thousands, with full PPAP Level 3 documentation.
Key Specifications
| Parameter | Specification |
|---|---|
| Material | AISI 8620 / 16MnCr5 case-hardening steel |
| Manufacturing Process | Silica sol investment casting + CNC machining |
| Heat Treatment | Carburized & quenched: 58–62 HRC case, 30–42 HRC core (per spec) |
| Critical Tolerances | Hub bore IT7; fork pad parallelism ≤ 0.05 mm |
| Casting Tolerance | ISO 8062 CT5 |
| Weight Range | 0.15–1.5 kg |
| Inspection | 100% fork-opening gap gauging, CMM layout per PPAP plan, MT crack check |
| Documentation | PPAP Level 3, EN 10204 3.1 certificates, capability studies (Cpk ≥ 1.33) |
| Applications | Manual transmissions, DCT, transfer cases, off-highway gearboxes |
Why Investment Casting Wins on Shift Forks
Shift forks have thin walls, deep fork slots, and offset geometry that are expensive to machine from bar or forging blanks—up to 60% of the material becomes chips. Investment casting produces the fork slot and pad geometry near the net shape, cutting machining content dramatically, while the fine-grain 8620 casting maintains the fatigue strength the part requires. Result: lower per-part cost with identical or better function, at both prototype and serial volumes.
Why Choose Ningbo Ruican
- IATF 16949 certified—transmission component experience with PPAP, APQP, and SPC
- Integrated heat treatment control—carburizing depth and hardness verified every batch
- Prototype speed: first article castings in 2–3 weeks from drawing release
- Gauge and fixture development in-house for 100% inspection of critical fork geometry
- Multi-material capability: 8620, 20MnCr5, 42CrMo4, and powder-metal alternatives priced side-by-side
