The ACDelco / GM 12673657 is the OE serpentine drive belt tensioner for 2017–2025 Chevrolet Silverado and GMC Sierra 2500 HD / 3500 HD with the 6.6L Duramax diesel.

Features & Benefits

• OE drive belt tensioner assembly, GM P/N 12673657
• Helps keep the drive belt at correct tension to maintain proper function (per GM)
• GM lists it for the main serpentine belt on 6.6L diesel with and without dual generators
• GM shows a newer supersession (12749242) at some dealers
• Genuine GM / ACDelco OE part, designed, engineered and tested to GM standards and backed by General Motors

Application

• Chevrolet Silverado 2500 HD / 3500 HD and GMC Sierra 2500 HD / 3500 HD with 6.6L Duramax diesel (2017–2025)

Always verify fitment by VIN or by matching the GM/ACDelco part number on your original part before ordering.

Cross-Reference / OE Numbers

• GM: 12673657
• Newer GM number shown by some dealers: 12749242