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Spare Parts for Dongfeng Truck QSB6.7 Engine Belt Tensioner 3976834

The Cummins 3976834 Automatic Belt Tensioner Assembly is an original equipment (OE) component designed to maintain optimal tension on the engine’s serpentine or multi-V belt drive system. As a critical part of the front-end accessory drive (FEAD), it ensures reliable power transmission to essential accessories such as the alternator, water pump, air conditioning compressor, and power steering pump.

Featuring an automatic self-adjusting mechanism with integrated damping, this tensioner compensates for belt stretch, thermal expansion, and engine vibration — preventing slippage, reducing noise, and extending the life of both the belt and driven components. It is widely used across Cummins ISB, QSB, 6BT, and ISDe series engines, making it a staple in medium-duty trucks, commercial vehicles, construction equipment, and generator sets.

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Model:
3976834
Brand:
Dongfeng

Product Description

Attribute	Description
Product Name	Automatic Belt Tensioner / Serpentine Belt Tensioner
Function	Maintains constant belt tension; absorbs shock and vibration from engine operation
Type	Spring-loaded automatic tensioner with built-in damper
Housing Material	High-strength cast aluminum alloy (lightweight and corrosion-resistant)
Spring Mechanism	Precision-calibrated torsion spring made from high-carbon steel
Pulley (Idler Wheel)	Steel or reinforced composite pulley with sealed ball bearing
Operating Principle	Automatically adjusts position via spring force while damping oscillations through internal friction or hydraulic-like resistance
Mounting Style	Bolt-on flange mount with single central fastener

Parameter	Specification
Part Number (OEM)	3976834
Common Replacement No.	3957434
Pulley Diameter	~74–76 mm
Pulley Width	~32–38 mm (compatible with PK-profile multi-ribbed belts)
Belt Compatibility	Multi-V belts (e.g., 6PK, 8PK), commonly used in FEAD systems
Torque Range	Designed to apply consistent force (~100–180 N depending on engine load)
Damping Performance	Integrated mechanical damping to suppress harmonic vibrations
Design Life	Matches mid-rebuild interval — typically 150,000–200,000 km under normal conditions
Environmental Resistance	Corrosion-resistant coating; operates reliably in temperatures from -30°C to +120°C
Lubrication	Factory-sealed unit — no maintenance or re-lubrication required