Swing Bearing for CAT 320C / 320D Excavator

Replacement swing circle · OEM reference 227-6081 and 148-4691 · 1316 x 1081 x 105 mm · 110 teeth

1316 mmOutside diameter

1081 mmBore diameter

105 mmOverall height

Z 110Gear teeth

This slewing ring is the swing bearing for the Caterpillar 320C and 320D excavators, covering both the standard undercarriage and the long-undercarriage variants. It is an aftermarket part manufactured by Lyhc — not a Caterpillar product. OEM references 227-6081 and 148-4691 are quoted for identification only.

The swing circle carries everything above the track frame: boom, stick, bucket, hydraulic tank and counterweight. On a 20-tonne class machine that is roughly 20 tonnes of upper structure rotating on a single raceway, so every swing cycle applies axial load, radial load and tilting moment at once. When a 320C starts to feel loose in the swing, or the operator reports a clunk at start and stop, this bearing — not the swing motor — is the usual cause.

The 320B ring will not fit this machine

This is the single most expensive mix-up in the 320 family, and it survives because both rings carry 110 teeth and look identical on a pallet.

Parameter	320B	320C / 320D
Outside diameter	1314 mm	1316 mm
Bore diameter	1084 mm	1081 mm
Overall height	100 mm	105 mm
Outer ring height	85 mm	73 mm
Inner ring height	87 mm	93 mm
Gear teeth	110	110
Outer bolt holes	33 x Ø22	42 x Ø22
Inner bolt holes	36 x M20	40 x M20

Two millimetres of outside diameter and five of height are enough to prevent the ring seating on the mounting face, and nine missing holes mean the bolt pattern will not line up at all. The same tooth count makes the error easy to miss until the machine is apart.

Specifications

Parameter	Value
Bearing type	Single-row four point contact ball slewing ring, external gear
Fits	CAT 320C, 320C L, 320C LN, 320D, 320D L, 320D LN
Outside diameter	1316 mm
Bore diameter	1081 mm
Overall height	105 mm
Outer ring axial height	73 mm
Inner ring axial height	93 mm
Gear teeth Z	110
Outer ring bolt holes	42 x Ø22
Inner ring bolt holes	40 x M20
OEM reference	227-6081 / 148-4691
Material	42CrMo, quenched and tempered
Raceway hardness	55-58 HRC, induction hardened
Gear hardness	50-56 HRC
Lubrication	Lithium EP grease, NLGI 2
Operating temperature	-25 C to +80 C

Which part number do you actually have?

Caterpillar issued more than one reference for this ring depending on undercarriage and market. 227-6081 covers the standard 320C; 148-4691 is commonly quoted for the 320C LN and 320D LN. Both resolve to the same 1316 x 1081 x 105 envelope in practice, but the safe route is the machine serial number, not the part number alone.

If the plate is unreadable, three measurements settle it: outside diameter 1316 mm, bore 1081 mm, and 42 bolt holes in the outer ring. Any ring measuring 1314 x 1084 with 33 outer holes is the 320B part and will not fit.

What kills a 320C swing bearing

Failure mode	What you see	Root cause
Raceway spalling	Metallic flakes in grease, rough rotation at one arc	Water ingress past the seal, or grease starvation
Tooth flank wear	Backlash grows, swing drifts when stopped	Swing brake dragging, or pinion misalignment
Seal damage	Grease weeping at the ring joint, dirt track	Pressure washing, or installation with a distorted seal
Bolt loosening	Clunk at start/stop, paint cracked around bolt heads	Insufficient preload, reused bolts, greasy interface
Raceway brinelling	Vibration and noise after transport or long idle	Static load with machine parked and boom extended

Before you install

1. Clean both mounting faces to bare metal. Grease or paint under the ring destroys the friction joint and the bolts will not hold preload.

2. Check flatness of the track frame and the upper structure. A distorted seat concentrates load on one arc of the raceway and shortens life regardless of bearing quality.

3. Use new bolts of the specified grade. Torque in a cross pattern over at least two passes.

4. Rotate the upper structure by hand before connecting the swing motor, to confirm the ring is seated and free.

5. Grease to the specified quantity after installation, then again after the first 50 operating hours.

Frequently asked questions

Will this fit a 320B?

No. The 320B uses a 1314 x 1084 x 100 mm ring with 33 outer bolt holes. This part is 1316 x 1081 x 105 mm with 42 outer holes.

Will it fit a 320D L or 320D LN?

Yes — the 320C and 320D share the same swing circle envelope. Confirm the undercarriage variant against the serial number if the machine has been reworked.

Will it fit a 330?

No. The 330 class uses a 1665 mm outside diameter ring, a completely different size and bolt pattern.

Is the gear hardened?

Tooth hardness is 50-56 HRC, induction hardened. State the required surface hardness and case depth on the order if the machine runs high swing duty.

Do you supply the mounting bolts?

Bolts are quoted separately by grade and quantity. Tell us the machine model and we will list the correct set with the quotation.

Can you confirm from a photo?

Usually. Send a photo of the old ring with a tape measure across the outside diameter and across the bore, plus the machine serial number. That is normally enough to confirm the size.

Request a drawing and quotation

Send the machine serial number, the old bearing photo or drawing, and the quantity. We confirm the size, issue a dimensioned drawing for approval, then manufacture. Contact Us.