Clutch and alternator freewheel components for HGVs
This collection covers two distinct product types. The primary stocked item is Hella alternator freewheel clutch pulleys, which are decoupling components fitted to the alternator shaft on many modern HGV engines. The collection also includes a Sachs clutch cover for DAF applications.
Alternator freewheel clutches (also called overrunning alternator pulleys or OAPs) replace conventional solid pulleys on the alternator. They contain a one-way clutch mechanism that decouples the alternator from the belt drive during engine deceleration, reducing belt slip and vibration. Failure symptoms include belt squeal, belt wear, alternator noise and in some cases charging faults. The Hella range covers thread sizes M14, M16 and M17 with groove counts from 5 to 8, in both capped and open configurations.
When selecting a freewheel clutch, the thread size and number of grooves must both match the existing unit exactly. These are not interchangeable across configurations. For the full Sachs clutch cover range in push and pull configurations, concentric slave cylinders and flywheels, see the Sachs collection.
Frequently asked questions
What is an alternator freewheel clutch?
An alternator freewheel clutch is a decoupling device fitted to the alternator pulley. It contains a one-way clutch that allows the alternator to spin freely during engine deceleration, reducing accessory belt stress and vibration. It replaces a conventional solid pulley and is application-specific.
How do I know if my alternator freewheel clutch has failed?
Common symptoms are accessory belt squeal on deceleration, unusual noise from the alternator, accelerated belt wear and intermittent charging faults. A failed freewheel clutch that has seized causes the alternator to over-drive the belt; one that has slipped will show reduced charging output.
How do I select the right Hella freewheel clutch?
You need the thread size (M14, M16 or M17) and the number of grooves (5, 6, 7 or 8) from the existing pulley. Both must match exactly. Whether the unit has a cap is also noted on the product listing. Cross-reference the Hella part number from the existing unit where possible.
Where are the full Sachs clutch covers listed?
The complete Sachs range including clutch covers in push and pull configurations, concentric slave cylinders for MAN and Renault Trucks, and flywheels for Scania and Mercedes is in the Sachs collection at truckstopgroup.co.uk/collections/sachs.
Can I get these parts delivered next day?
Yes. In-stock parts are available for next-day delivery to UK mainland addresses, or same-day collection from our branches in Redditch, Worcester, Birmingham and Evesham.
