Flywheel ring gear. Porsche 911 1970-86 / 930 1975-77  ❭  91111623904

Flywheel Ring Gear 

Restore dependable engine starting performance with this OE Match Flywheel Ring Gear, designed for Porsche 911 models produced between 1970 and 1986. The flywheel ring gear is a critical component of the engine starting system, providing the engagement surface for the starter motor and allowing the engine to crank reliably every time the ignition is activated.

Fits:

• Porsche 911 1968-1973 2.2L / 2.4L / 2.7L RS LWB (F)
• Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
• Porsche 911 1978-1983 3.0L / SC
• Porsche 911 1984-1986 3.2L
• Porsche 911 1975-1977 3.0L Turbo (930)

Manufactured to OE specifications, this replacement ring gear delivers the correct tooth profile, fitment and durability required for classic air-cooled Porsche applications. Whether you're rebuilding an engine, replacing a worn flywheel component or restoring a classic 911, fitting a new flywheel ring gear helps ensure smooth starter operation and long-term reliability.

What Does the Flywheel Ring Gear Do?

The flywheel ring gear is a hardened steel gear mounted around the outer circumference of the flywheel. Its primary purpose is to engage with the starter motor pinion gear during engine start-up.

When the ignition key is turned, the starter motor extends its pinion gear into the teeth of the flywheel ring gear. The starter then rotates the flywheel, turning the engine over until combustion begins and the engine starts.

The flywheel ring gear plays a vital role by:

• Providing a durable engagement surface for the starter motor.
• Allowing the engine to crank during start-up.
• Ensuring smooth and reliable starter operation.
• Transferring rotational force from the starter motor to the crankshaft.
• Supporting consistent engine starting performance.

Without a properly functioning ring gear, starter engagement can become unreliable or impossible.

Why Do Flywheel Ring Gears Fail?

Although manufactured from hardened steel, flywheel ring gears experience repeated mechanical loading every time the vehicle is started. Over decades of service, wear and damage can occur.

Common causes of failure include:

• Tooth wear caused by repeated starter engagement.
• Damaged or chipped gear teeth.
• Starter motor misalignment.
• Worn starter pinion gears damaging the ring gear.
• Excessive heat generated during clutch or flywheel issues.
• Corrosion caused by moisture contamination.
• General wear associated with high mileage and age.

On classic Porsche 911 models, decades of repeated engine starts can eventually lead to worn sections of the ring gear, particularly in the areas where the engine most commonly stops after shutdown.

When Should the Flywheel Ring Gear Be Replaced?

The flywheel ring gear should be inspected whenever the engine, clutch or flywheel assembly is removed. Replacement is recommended if you observe:
Chipped, broken or heavily worn teeth.

• Starter grinding noises during engine start.
• Intermittent starter engagement problems.
• Difficulty cranking the engine.
• Visible corrosion or damage.
• Excessive wear around frequently engaged sections of the gear.
• During clutch replacement or engine rebuild projects when wear is evident.

Replacing a worn ring gear while the transmission or engine is already removed can prevent future starting problems and reduce labour costs.

Related reference numbers
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91111623904

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