Flywheel Shim
Representative Photo, actual item may vary
Representative Photo, actual item may vary
What Is a Flywheel Shim and Why Does It Matter?
A flywheel shim is a precisely machined spacer that sits between the flywheel and the engine crankshaft flange. It's one of those small, easy-to-overlook components that plays an outsized role in drivetrain health. Whether you're rebuilding a manual transmission or servicing an automatic, getting the flywheel's axial position exactly right is critical to clutch engagement, smooth power transfer, and long-term drivetrain durability.
When a flywheel is resurfaced — a common step during a clutch replacement — material is removed from its friction surface. ATP flywheel shims install easily, restoring machined manual transmission flywheels back to the proper height. Without compensating for this removed material, the clutch disc and pressure plate may not engage at the correct depth, leading to slipping, premature wear, or uncomfortable pedal feel. Improper clutch location can be dangerous and uncomfortable — a flywheel shim is the simple, cost-effective solution.
On automatic transmissions, the role of the shim shifts slightly but remains just as important. On automatic transmissions, the shim takes up excessive clearance caused by engine crankshaft endplay or by installing a rebuilt torque converter or rebuilt front pump. This makes flywheel shims a must-have component any time an automatic transmission is overhauled or a new torque converter is installed.
Key Considerations When Shopping for Flywheel Shims
- Thickness: Shims are available in multiple thicknesses (commonly 0.025 in. and 0.050 in.) to match exactly how much material was removed during resurfacing. Always measure your flywheel carefully before selecting a shim.
- Bolt Pattern & Fitment: Shims are available in a variety of thicknesses and bolt configurations for easy crankshaft-to-flywheel attachment. Always verify the hole count and bolt pattern matches your specific engine.
- Material: Most quality flywheel shims are constructed of steel for durability and dimensional stability under the heat and rotational forces generated in the bell housing.
- Application: Know whether you have a manual or automatic transmission — the functional role of the shim differs between the two, though both rely on precise fitment.
- Cost vs. Replacement: ATP shims save money by allowing the re-use of the flywheel rather than purchasing a costly replacement unit. For most resurfaced flywheels, a shim is the smarter, more economical path.
Top Flywheel Shim Brands
ATP Automotive is the top-selling flywheel shim brand, and for good reason. ATP Automotive is proudly owned by Pioneer Automotive Industries, a company with over 80 years of experience in precision engineering and manufacturing. Their flywheel shim lineup covers a wide range of domestic and import applications, from GM A-body platforms to Nissan classics, making them a reliable go-to for professional technicians and DIY enthusiasts alike.
McLeod Racing is a respected name in performance clutch and drivetrain components, trusted widely in the racing and high-performance street community. Their flywheel shims are engineered to the same exacting tolerances as their clutch kits, ensuring a precision fit when pairing with performance flywheel setups.
EMPI has long been a staple in the air-cooled Volkswagen and specialty import market, offering a range of drivetrain components including flywheel shims tailored to classic VW and Bug applications — a great resource for enthusiasts restoring vintage vehicles.
Mr. Gasket is a well-known American performance brand with decades of experience producing sealing and drivetrain accessories. Their flywheel shims reflect the brand's commitment to quality fitment and are a solid choice for domestic performance and street builds.