DISC 6Y7952 - Caterpillar

All Caterpillar MachinesTwo different alternator designs are used on Caterpillar machines. The difference in designs is the way the drive pulley is held on the rotor shaft of the alternator. On one design, the pulley is held on the rotor shaft only by a retaining nut. This design can be recognized by a 5/16" hex socket which is on the end of the rotor shaft. The other design utilizes a Woodruff key and a retaining nut to hold the drive pulley in place. It can be recognized by the key slot in the rotor shaft. Also, it does not have a hex socket on the end of the rotor shaft.
When replacing an alternator of either design, be sure the drive pulley retaining nut is tightened to the correct specified torque value. This will prevent possible damage to the pulley, alternator and vee belt used to drive the alternator. Refer to the appropriate service manual for this specification. The chart which follows lists the most common alternator's used on Caterpillar machines. Also, listed is the torque value required for the nut which holds the drive pulley in position on the alternator.
On alternators without a Woodruff key, a 5/16" allen wrench can be used to hold the rotor shaft from turning while the retaining nut is being tightened. Do not use an impact wrench to tighten the retaining nut on either design.
On alternators with a Woodruff key, it is not necessary to use the key if the retaining nut which holds the drive pulley is tightened to the specified torque value.