Product Description
Mitchell 84331 Pinion Assembly – Genuine Part for 310UL (Ultralight)
The Mitchell 84331 Pinion Assembly is the high-precision "business end" of the drivetrain for the Mitchell 310UL (Ultralight) spinning reel. As a primary component in this modernized ultralight chassis, the pinion gear is responsible for turning the rotor while simultaneously allowing the main shaft to slide through its center to provide spool oscillation.
This assembly typically includes the pinion gear itself and, in some kit versions, the supporting sleeve or bearing interface. Because the 310UL is designed for finesse fishing with light lines, the 84331 is machined to exacting tolerances to ensure a "whisper-quiet" retrieve and zero-binding performance.
Product Specifications
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Part Number: 84331
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Component Type: Pinion Gear Assembly
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Application: Ultralight (UL) Series
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Material: High-grade Marine Brass or Hardened Alloy
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Origin: Genuine Mitchell Engineering
Compatible Models
The 84331 pinion assembly is the standard replacement for the modernized small-body Mitchell series. It is a verified fit for:
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Mitchell 310UL (Modern Ultralight Series)
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Mitchell 310Xe
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Mitchell 310 Pro
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Mitchell 310 (Select early 2000s-era variants)
Technical Insight: The 310UL represents a shift from the classic 1960s "round body" design to a more modern, compact geometry. The 84331 pinion must be perfectly meshed with the Main Drive Gear. If you are replacing this part due to "grittiness" in the handle, it is vital to inspect the teeth of the drive gear as well; a damaged pinion will often transfer wear to its companion gear. You can verify your specific model's internal layout at www.reelschematic.com.
Professional Maintenance & Lubrication
Because ultralight reels have smaller gear teeth, they are more sensitive to lubrication quality. Proper care ensures the 310UL maintains its signature smooth feel.
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Pinion Teeth: Apply a light, precise coating of Deuthlon Reel Grease to the pinion teeth. Its "Dust-Shield" properties are especially beneficial for ultralight reels, as they provide a protective barrier against micro-debris that can easily foul small-scale gears.
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Internal Bore: Apply one drop of Deuthlon Reel Oil to the internal channel of the pinion gear. This ensures the main spindle travels back and forth with zero friction, which is essential for the sensitive drag performance required when using 2lb or 4lb test line.
Why Choose Genuine Mitchell 84331?
The Mitchell 84331 is factory-balanced to prevent the rotor wobble that often occurs with generic or poorly machined aftermarket parts. In a reel as small as the 310UL, even a minor imbalance can be felt through the rod blank. A genuine replacement ensures that the gear ratio and tooth pitch remain exactly as intended by the engineers, preserving the mechanical longevity and smooth operation of your finesse setup.
