Federal Military Parts (763) 310-9340
Overrunning Clutch Serpentine Pulley, Fits M1114 Hummer, 12469483 , 600634
Ordinarie pris
42.000 DJF
Ordinarie pris
Försäljningspris
42.000 DJF
Enhetspris
per
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The HMMWV 8-groove over-running alternator/clutch pulley (often found on 200A systems) enables the serpentine belt to drive the alternator smoothly while preventing the alternator's high-inertia rotor from back-driving the belt during engine deceleration. This extends belt life and prevents system damage.
The primary National Stock Number (NSN) for a Humvee (HMMWV) overrunning clutch 8-groove alternator pulley is 3020-01-491-2671.
Key Replacement Specs & Details
- Part Numbers: 12469483, 12469186
- NSN: 3020-01-491-2671 or 3020-01-444-5447
- Belt Type: 8-groove serpentine
- Application: Specifically fits HMMWV variants (including M998, M1025, M1123, and M1151) outfitted with heavy-duty 200-amp alternators.
The HMMWV 8-groove over-running alternator pulley installation requires specialized removal tools and precise torque application to prevent belt slippage or component damage.
Required Tools
- OAP Removal Tool: Spline tool set (specifically a 33-spline alternator socket) to hold the pulley while turning the shaft.
- Impact Wrench: Air or cordless impact wrench for effortless removal of the old pulley.
- Torque Wrench: Metric torque wrench capable of reaching factory specifications.
- Hex or Torx Bits: Shaft-end bits (typically 10mm hex or T50 Torx) to hold the center spindle if hand tools are used.
- Breaker Bar: Long handle bar for manual leverage.
Step-by-Step Installation Process
- Disconnect Battery: Disconnect the negative battery cables to prevent electrical shorts. [1]
- Remove Serpentine Belt: Rotate the belt tensioner to release tension and slide the 8-groove belt off the pulley.
- Unbolt Alternator: Remove the mounting bolts to extract the 200A alternator from the engine bay for better workbench access.
- Remove Old Pulley: Insert the 33-spline tool into the pulley, lock the center shaft with your hex/Torx bit, and rotate counter-clockwise to loosen.
- Thread New Pulley: Hand-thread the new pulley (Part #12469483 or #12469186) clockwise onto the alternator rotor shaft to prevent cross-threading.
- Torque to Spec: Use the spline tool and torque wrench to tighten the new pulley firmly against the shaft shoulder (typically 60-65 ft-lbs / 80-88 Nm).
- Reinstall Components: Mount the alternator back to the bracket, route the serpentine belt, and reconnect the batteries.
Pro Installation Tips
- Direction of Rotation: Over-running alternator pulleys (OAP) always tighten in the direction of normal engine rotation (clockwise from the front) and loosen counter-clockwise.
- Inspect the Tensioner: Always check the automatic belt tensioner and idler pulleys for bearing wear while the serpentine belt is removed.
- Shaft Cleanliness: Clean the alternator rotor shaft threads with a wire brush and brake cleaner before installing the new clutch pulley to ensure accurate torque.
This component is an Overrunning Alternator Clutch (OAC) Pulley, specifically engineered for military application on the M1114 Up-Armored Humvee (HMMWV) and its heavy-duty variants [3020-01-491-2671].
At a high-level glance, its standout sorting feature is its size—sporting a large 4-1/4 inch (4.25") outer diameter with an 8-groove serpentine belt track. This makes it immediately distinguishable from smaller 3-inch commercial pulleys or much larger 6-inch industrial pulleys.
What Makes This Pulley Unique?
Unlike a standard, solid metal pulley that is bolted directly to an alternator shaft, this is a highly specialized one-way clutch mechanism.
- The Engine Overrun Problem: The heavy-duty 200-amp and 400-amp dual-voltage alternators used in up-armored Humvees feature massive, heavy internal rotors. When the Humvee's 6.5L Turbo Diesel engine rapidly changes speeds (like during sudden braking, gear shifts, or tactical maneuvers), the heavy alternator rotor wants to keep spinning fast due to its own momentum.
- How It Fixes It: If the pulley were solid, that sudden speed mismatch would force the serpentine belt to slip, squeal, and rapidly burn out. This overrunning pulley features internal roller bearings that allow the alternator's internals to safely "coast" or free-wheel forward when the engine slows down.
Quick-Reference Identification Guide
If someone is holding this part in their hand trying to verify it against other items in a workshop, they should look for these distinct markers:
- The 4-1/4" Scale: Sits right in the sweet spot between standard automotive pulleys and heavy equipment pulleys.
- The 8-Groove Ribs: The outer face features exactly 8 precise V-shaped tracks to grab the heavy-duty engine belt.
- The 33-Spline Center Eye: Looking straight into the front face, the inner mounting hole isn't smooth or keyed; it features a distinct ring of 33 internal teeth (splines). This requires a specific multi-spline tool to lock the clutch during installation or removal.
