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Overrunning alternator pulley: replacement and selection

When and why it is necessary to replace overrunning alternator pulley

Average lifetime limit of the overrunning alternator pulley is 100,000 – 150,000 kilometers of mileage. Premature replacement of the component can be required due to corrosion, abrasive or mechanical wear of the sleeves, and their misalignment. Moreover, the sleeves break sometimes, leading to falling out of the rollers, and inability of the pulley to be engaged with the alternator shaft.

The main cause of corrosion and abrasive wear-out of the part is its operation without protective cap on. Ingress of dirt or water into the overrunning mechanism quickly breaks it down. Premature abrasion of the part can be caused by improper installation of the belt or alternator (for example, with a displacement). Moreover, the overrunning clutch can be damaged due to impact in a road accident.

The characteristic sign of component defect is rattling sound in the passenger compartment. Apart from this, vibration of the drive belt increases at movement of the car at low speed. This can be noticeable in the passenger compartment. Also, defects of the alternator clutch pulley can be indicated by clicking sound from under the hood, failures in operation of the car electric equipment. In addition, premature wear-out of the drive belt, rollers and hydraulic tensioner can be the signs of the car part defectiveness.

Replacement of the overrunning clutch pulley is performed at a service station, as for demounting of this part a special remover tool is necessary. Moreover, in most cases, access to the part is complicated: you will need to demount the other components. It is recommended to replace the alternator belt, tensioner and all drive rollers together with the clutch pulley.

How to select overrunning alternator pulley

By operation principle these parts are divided into two types: freewheel clutch and reversing clutch. The components of both types rotate freely in one direction, but the first ones are immediately locked at rotation in other direction, while the second ones allow for slight angle displacement.

The freewheel pulleys are divided into friction and ratchet ones. The friction ones differ from one another by construction, and there can be spring, band and wedge clutches. A version of the wedge-type components are roller pulleys, which are most often installed into modern cars.

In order to make the overrunning alternator pulley faultlessly serve you for its entire operation lifetime, give preference to products from proven manufacturers. High quality components are presented in the assortment of Bosch, Valeo, Ruville, Triscan, Magneti Marelli and other brands.

The overrunning pulley should be selected accordingly to the type and power of the alternator. Moreover, you need to take into account width, depth, outer and inner diameter of the part, quantity of its splines. Also no less important parameters for component proper installation are size and pitch of thread. Pay attention also to presence of a protective cap in the kit. In some cases the overrunning pulleys are sold without it.