3069512 Swing 1st Sun Gear 24T for HITACHI Excavator

3069512 Swing 1st Sun Gear

The 3069512 sun gear is used inside the swing reduction gearbox of selected Hitachi excavators. Its compact gear body and internal spline allow rotational input to be transferred into the planetary reduction stage as the excavator upper structure swings.

Unlike a long cylindrical sun gear, this design combines a relatively short external gear section with an internally splined center. Both the external tooth profile and the spline fit are therefore important when checking a replacement.

Correct engagement helps maintain stable torque transfer during repeated swing acceleration, braking and direction changes.

Two Working Surfaces Need Attention

This type of sun gear has two important contact areas: the external gear teeth that mesh with the planetary gears and the internal spline that connects the gear to its driving component.

Wear on either area can create excessive clearance. Damaged external teeth may affect planetary gear engagement, while a worn internal spline can produce movement between connected components even when the outer teeth still appear usable.

For this reason, both sides of the original gear should be inspected before the swing gearbox is rebuilt.

Common Wear Found on a Used Swing Sun Gear

When the swing reduction gearbox is disassembled, check the original gear for:

• Pitting or flaking on the external gear teeth

• Chipped or cracked tooth edges

• Rounded or worn internal spline teeth

• Uneven contact marks across the gear width

• Heat discoloration caused by poor lubrication

• Metal particles in the swing gearbox oil

Heavy wear on only one side of the gear may indicate an alignment, bearing or carrier problem elsewhere in the reduction gearbox.

Confirm Both Gear Teeth and Internal Spline

Similar swing gears can have almost the same outside appearance while using a different spline profile, gear width or tooth configuration.

Checking only the excavator model or outside diameter is therefore not enough. The original part should be compared for external tooth count, internal spline count, overall width and bore dimensions.

Machine serial information and swing gearbox details are also useful when the excavator has previously received a replacement swing device.

Information for Fitment Verification

For a more reliable match, send the following information with your inquiry:

• Excavator model and machine serial number

• Swing gearbox or swing device information

• Clear photos of both sides of the original gear

• External tooth count

• Internal spline count and bore diameter

• Outside diameter and overall gear width

These details help distinguish similar swing sun gears before shipment.

Swing Gear Parts Support from Topvelsun

Topvelsun supplies replacement sun gears and other internal swing reduction components for excavator repair shops, equipment owners and parts distributors.

Send us part number 3069512 or cross reference AT213758 together with your machine and original gear information, and we can help verify the application before quotation.