Product Description
Shimano 10DK0 Idle Gear (RD18744)
The Shimano 10DK0 Idle Gear (RD18744) is a specialized internal gear responsible for the synchronization of the spool's oscillation in Shimano spinning reels. It acts as the mechanical bridge between the pinion gear and the oscillation gear (which drives the worm shaft or oscillation slider).
In modern Shimano spinning reels, this gear is often part of the Aero Wrap II or Slow Oscillation systems. Its role is to ensure that the spool moves up and down at a precise speed relative to the rotor's rotation. This precision is what creates the perfect parallel line lay that allows for longer casts and fewer wind knots. Because it is typically made of a high-durability polymer to reduce weight and noise, the teeth can wear down or chip if the reel is subjected to sudden shocks or "sand-cranking."
Product Specifications
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Part Name: Idle Gear
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Part Number: 10DK0
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Shimano Code: RD18744
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Material: High-Impact Composite / Engineering Polymer
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Function: Drive transmission for the oscillation system (spool stroke).
Alternate Part Numbers
This part is a standard component in the modern Shimano spinning reel catalog and is identified as:
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RD18744
Compatibility & Fitment
The 10DK0 (RD18744) is utilized in many of Shimano’s mid-to-high-tier spinning reels produced from 2017 onwards. It is a direct factory fit for the following series:
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Shimano Stradic Series: ST-2500HGFL, ST-C3000HGFL, ST-4000FL, ST-C5000XGFL
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Shimano Vanford Series: VF-2500, VF-C3000, VF-4000, VF-C5000XG
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Shimano Ultegra Series: UL-2500FC, UL-C3000FC, UL-4000FC (Series models)
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Shimano Miravel Series: All sizes utilizing the RD18744 specification.
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Shimano Sustain Series: SA-2500FJ, SA-C3000FJ, SA-4000FJ
Key Features
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Silent Drive Integration: Engineered with a specific tooth pitch to minimize vibration and gear "whirr" during a slow retrieve.
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Lightweight Design: Constructed from advanced polymers to reduce the rotational inertia of the reel.
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Precision Timing: Maintains the exact gear ratio required for the spool to complete its vertical cycle without overlapping line incorrectly.
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Self-Lubricating Properties: The material is designed to hold grease effectively, reducing the frequency of internal maintenance.
Maintenance & Troubleshooting
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Symptom of Failure: If your spool stops moving up and down while the rotor still spins, or if you feel a "skip" every few turns of the handle, the teeth on the 10DK0 are likely stripped.
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Lubrication: When installing a new gear, use a high-quality synthetic grease like Shimano DG06 (Ship Grease). Avoid heavy drag greases on this part, as they can cause the oscillation to feel sluggish.
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Inspection: Check the Oscillation Gear and the Pinion Gear teeth for any debris. A tiny grain of sand caught in these gears is the most common cause of a stripped 10DK0 idle gear.
Pro Tip: For a complete visual of how this gear seats within the reel's body and interacts with the oscillation slider, refer to the PDF schematics at www.reelschematic.com.
