PRO / SPORT Under Drive

PRO/SPORT Under Drive Dampers & Pulley Kits feature :

• 25% Underdrive

• SFI Spec. 18.1 Bonded Harmonic Damper

• High quality “All Steel” construction

• Robust outer ring retention design

• Spin tested to 12,500 rpm

• 60o precision engraved timing marks

• Clear baked paint finish


Tested at 18,000 RPM at the official SFI Test Lab

PRO/SPORT Under Drive Dampers and Pulley Application (Click Here)

The PRO/SPORT Under Drive Dampers

Accessory drive systems have been made more compact on Late Model V8 engines like the Ford 4.6L and the GM LS1 by machining serpentine belt grooves on the OD of the crankshaft damper. The crankshaft damper functions as a combination crank damper and crank pulley on these engines. Under drive dampers are smaller in diameter than stock production crank dampers which slows the speed of the accessories and reduces the HP required to drive them. Since performance and racing engine applications generally run at higher RPM, the water pump, alternator and power steering pump speeds can be reduced to save HP and still meet engine cooling, electrical and vehicle steering requirements.

The trick is to reduce the crank damper diameter without losing the torsion control capability required to prevent engine vibration and possible damage. The PRO/SPORT Under Drive dampers have been specially tuned to control crankshaft torsional vibration to stock production levels.

Dynamometer tests of the PRO/SPORT 25% under drive damper on a 2005 Mustang 4.6L 3V engine at Livernois Motorsports in Dearborn Heights, Michigan produced a 13 HP gain over a stock production damper.

Warning: Engine cooling and battery charging will be reduced and may not be adequate for city driving.

1996 & later FORD MUSTANG 4.6L V8 ENGINES

• Available in Damper only or Damper & Pulley Kit configuration
• 25% Under Driven Poly-V groove design.
• All Steel Water Pump pulley is finished in black baked enamel.
• Steel Alternator Pulley finished in black baked enamel (where supplied).
• Kit contains new crank bolt, installation bolt & alternator bracket bolt.


• 25% Under Driven front Poly-V groove accessory drive.
• 22% Under Driven rear A/C Poly-V groove on 98-05 Camaro & Firebird & 04-06 GTO LS1 & LS2 models.
• 7% Under Driven rear A/C Poly-V groove on 97-06 LS1, LS2, LS3 & LS6 Corvette models, Pontiac G8 L98, LS3.
• Steel Alternator Pulley finished in black powder coat (where supplied).
• Keyway

GM Truck Engines

• Available in damper only or damper & pulley kit configuration.
• 25% Under Driven Poly-V groove damper.
• 1.75” overdrive Steel Alternator pulley finished in black baked enamel supplied in kit configuration.

Note: NEW OEM crank bolt (GM Part# 12557840) and NEW belts are required when installing the dampers.

Dodge / Hemi Car and Truck Engines

• New under drive applications for 5.7L Hemi Car and Truck!
• 20 % Under Drive Poly-V groove damper.