Genuine GM Crankshaft Assembly 12708884 – Suits Gen V 6.6L L8T V8 (Silverado/Sierra HD)

Genuine GM Crankshaft Assembly 12708884 (supersedes part number 12701676) is a factory-forged steel crankshaft designed for the GM Gen V 6.6 L L8T V8 engine. This crankshaft features a 3.860″ stroke, integrated 58-tooth reluctor wheel, and 8-bolt flywheel flange—making it the direct replacement for high-demand Silverado/Sierra HD applications.

Manufactured from high-strength forged 1053/4340 steel and precision-balanced to OEM standards, the 12708884 crankshaft delivers exceptional durability for heavy-duty, towing or performance use. Each unit includes the pre-installed reluctor ring for seamless integration with GM engine management systems.

Fitment:

• Chevrolet Silverado / GMC Sierra HD (6.6 L L8T V8 – Gen V)
• GM performance builds using the Gen V 6.6 L L8T engine

Specifications:

• OEM Part Number: 12708884 (replaces 12701676)
• Engine: GM Gen V 6.6 L L8T V8
• Stroke: 3.860 in (98.0 mm)
• Reluctor: 58-tooth – Installed
• Flywheel Mount: 8-bolt pattern
• Material: Forged 1053 / 4340 steel
• Balance: Internal – neutral counterweight design

Key Features:

• Genuine GM OEM crankshaft – factory specification for L8T applications
• Forged steel construction for maximum strength and reliability under heavy loads
• Pre-installed 58-tooth reluctor ensures accurate crank position signal
• Precision-balanced and heat-treated for smooth, long-life operation
• Ideal for factory rebuilds or performance/towing builds using the Gen V 6.6 L engine

Installation Tip: Fully clean oil galleries and journals before installation. Use new main and rod bearings, torque bolts to factory specs, and balance the rotating assembly if mixing aftermarket components.