Product Overview
The NA186338 / N191433 Gear & Pinion Set is a precision-engineered direct-fit transmission replacement for 4-1/2″ (115mm) corded angle grinders built on this common platform. This set includes both the primary bevel gear and the matching pinion gear as a pre-matched assembly – eliminating the guesswork of individual component selection and ensuring correct tooth contact pattern from the first installation[reference:0][reference:1].
Designed for professional repair technicians and equipment maintenance specialists, this gear set restores factory-spec power transmission to tools exhibiting grinding stalling, loss of torque under load, excessive gear noise, or complete drive failure. The case-hardened alloy steel construction and precision-ground tooth profiles deliver the durability required for continuous heavy-duty grinding, cutting, and surface conditioning operations.
Critical Note on Part Number Interchangeability: NA186338 and N191433 are functionally identical and fully interchangeable. N191433 has been superseded by NA186338 in many regions[reference:2][reference:3][reference:4][reference:5]. This listing supplies the current-spec NA186338 set, which is the direct replacement for both part numbers.
💡 Pro Tip – Pre-Installation Diagnostic: Before tearing into the gear case, perform a no-load amp draw test with a clamp meter. A healthy 4-1/2″ grinder should draw approximately 4–6A at no load. Draws exceeding 8A with the disc spinning freely indicate either failing gearbox bearings or a gear set with excessive tooth wear – both resolved by this complete gear and pinion replacement. Always disconnect the tool from mains power and allow the motor to cool before beginning disassembly.
Diagnostic & Fitment – When to Replace
Specification Comparison
| Specification | Worn / Generic Aftermarket | FixPartHub Precision Replacement ✅ |
|---|---|---|
| Tooth Hardness | Surface-hardened only – rapid wear | Case-carburized, through-hardened core |
| Tooth Profile Accuracy | Inconsistent – noise & vibration | Precision-ground – smooth meshing |
| Material Grade | Low-grade carbon steel | High-grade alloy steel – extended service life |
| Set Matching | Individual components – mismatch risk | Pre-matched gear + pinion – correct contact pattern |
| Pitting & Spalling Resistance | Prone to surface fatigue | Heat-treated – resists contact fatigue |
Teardown & Replacement Workflow
Compatibility – Cross-Reference & OEM Part Numbers
Diagnostic Q&A
❓ Q: My grinder runs but the disc doesn’t turn – is this definitely the gear set?
A: Not always. First verify that the spindle lock isn’t engaged and the disc isn’t seized. If the motor spins freely but the disc remains stationary, the gear set has likely stripped or the pinion has sheared. Remove the gear case and inspect the gears – any missing teeth or excessive wear confirms the need for replacement.
❓ Q: What’s the difference between NA186338 and N191433 – which one do I need?
A: NA186338 and N191433 are functionally identical and fully interchangeable. N191433 has been superseded by NA186338 in most regions[reference:6][reference:7][reference:8]. This listing supplies the current-spec NA186338 set, which is the direct replacement for both part numbers across all compatible grinder models.
❓ Q: What grease should I use when reinstalling the gear set?
A: Use a high-temperature, lithium-based or synthetic EP (extreme pressure) grease rated for gear applications – NLGI Grade 2 with molybdenum disulfide or similar anti-wear additives. Apply approximately 15–20g evenly across the gear teeth and bearing surfaces. Avoid over-greasing, which can cause overheating and premature seal failure.
❓ Q: Will this gear set fit my D28113K model?
A: Yes. The D28113K shares the same gear case and transmission components as the standard D28113[reference:9]. This NA186338 gear set is a direct-fit replacement for all D28113 variants, including the K (kit) version.
Safety Notes
- 🔴 Always disconnect the tool from mains power before beginning any disassembly or gear replacement procedure.
- ⚡ Allow the tool to cool completely before handling internal components – gears and gear case can reach high temperatures during operation.
- 🔧 Use correct torque values – gear case screws typically require 2.0–2.5 Nm (18–22 in-lbs). Over-torquing can strip housing threads or distort the gear case alignment.
- 🧤 Wear cut-resistant gloves when handling gears – machined tooth surfaces can have sharp edges.
- 📐 Verify gear mesh before final assembly – the gears should rotate smoothly with no binding or tight spots.
- ✅ Perform a no-load test before reinstalling the disc and guard – verify smooth operation and correct rotation direction.
A: Perform a “stall test” under load. With a fresh grinding disc installed, apply moderate pressure to a scrap piece of metal. If the grinder bogs down significantly or the disc stops rotating while the motor continues to run, the gear set is slipping – indicating worn teeth or a stripped pinion. Additionally, listen for a high-pitched whine or grinding noise during free spinning – this indicates excessive tooth wear or pitting.
A: Yes. NA186338 and N191433 are fully interchangeable. N191433 has been officially superseded by NA186338 in most markets. This listing supplies the current-spec NA186338 set, which serves as the direct replacement for both part numbers across all compatible grinder models.
A: This gear set is compatible with DWE8100S, DWE8100T, DWE8110S, DWE8111S, DWE8101S, DWE8101T, D28113, D28134, and D2811 models. Always verify your tool’s model number against the compatibility list before ordering.
A: Always replace both the gear and pinion as a matched set. Gears wear together and develop a specific tooth contact pattern. Mixing a new gear with a worn pinion (or vice versa) will result in improper mesh, accelerated wear, and premature failure of both components. This listing includes both as a complete set.
