Caterpillarwork toolcold planer

Caterpillar PC9

Maintenance schedule, common problems & OEM parts breakdown

The Cat PC9 is a passive, carrier-hydraulics-driven cold planer built for skid-steer loaders and compact track loaders, mounted through the Cat skid-steer universal quick-coupler. It carries no engine and no ECM; all cutting power comes from the host machine's auxiliary hydraulic circuit driving an axial-piston motor that feeds a double-reduction planetary gearbox mounted inside the drum itself. The PC9 is the largest and highest-flow member of Cat's legacy small cold-planer line for skid-steer carriers, which spans the standard-flow PC3 and PC4 and the high-flow PC6 and PC9. With a drum width up to 812 mm (32 in) and an operating weight of roughly 915 kg (2017 lb), it needs approximately 95-125 L/min (25-33 gpm) at 193-345 bar (2800-5000 psi) of carrier hydraulic flow, placing it firmly in the high-flow-carrier class alongside the PC6 rather than the lower-flow PC3/PC4 pair.

In today's used and parts market, the PC9 sits at the top of a thin-documentation legacy line that Cat has since replaced in its current catalog with a differently numbered PC1xx/2xx/3xx/4xx cold-planer series; the two numbering schemes are not interchangeable and specs should never be crossed between them. No factory serial-prefix table for the PC9 is publicly documented, which is normal for a niche, low-volume attachment rather than a sign of missing records. Buyers value the PC9 specifically for its high-flow drum drive and full 812 mm cut width on compact carriers, a combination the standard-flow PC3/PC4 pair cannot match, so used units and gearbox/drum parts trade at a premium over the smaller siblings in the same family.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.

Caterpillar PC9 specifications

Engine

Power source	No onboard engine. PC9 is a passive, carrier-driven skid steer loader work tool; cutting drum is turned by the host machine's high-flow auxiliary hydraulic circuit.
Drive motor	Variable-speed, unidirectional axial piston hydraulic motor mounted to a double-reduction planetary gearbox. Gearbox sits inside the drum so drum inertia dampens load spikes.
Emissions tier	Not applicable — no engine on the tool itself.

Weights

Operating weight (tool only)	915 kg (2017 lb), standard all-purpose bit configuration
Shipping weight	Not separately published; matches operating weight for this attachment class
Ground pressure	Not published as a figure. Four pivoting skids are stated to limit ground pressure and provide a stable planing platform, but no PSI/kPa value is given

Dimensions

Overall width	1676 mm (66 in)
Maximum drum/working width	812 mm (32 in)
Overall height	810 mm (32 in)
Overall length	1320 mm (52 in)
Cut diameter (drum)	549 mm (21.6 in)
Sideshift travel	600 mm (23.6 in), hydraulically controlled from the operator's compartment
Tilt angle range	±15°, hydraulic cylinder controlled via electrohydraulic valve

Performance

Drum torque at max pressure	4015 N·m (2952 lb-ft)
Drum speed at max flow	171 rpm
Bit speed at max flow	296 m/min (969 ft/min)
Maximum mechanical depth of cut	152 mm (6 in)
Productive milling depth	Greater than 76 mm (3 in) in asphalt; up to 16 mm (0.63 in) in concrete — this is the high-production planing range for the PC6/PC9 high-flow pair, distinct from the smaller PC3/PC4 standard-flow planers
Carrier compatibility / gradeability	No independent travel/gradeability rating — figures follow the host skid steer loader. Factory-approved for optimum performance only on the largest high-flow carrier in the line at the time (248-class); use on the next size down (228-class) carries a lift-arm hinge-pin height restriction of 1 m (3 ft) to avoid tipping. Smaller/standard-flow carriers are not approved, since the PC9 requires high-flow auxiliary hydraulics

Service capacities (summary)

Required hydraulic flow range	95-125 L/min (25-33 gpm), high-flow auxiliary circuit
Optimal hydraulic pressure range	193-345 bar (2800-5000 psi)
Fuel tank	Not applicable — no engine on the tool
Engine oil	Not applicable — no engine on the tool
Cooling system	Not applicable — no engine on the tool

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

PC9 fluids & capacities

System	Capacity	Recommended fluid
Engine crankcase (with filter)	Not applicable	The PC9 has no onboard engine. It is a passive high-flow cold planer attachment driven entirely by the host skid steer loader's hydraulic system.
Cooling system	Not applicable	No coolant system on the attachment itself. Cooling is handled by the carrier machine.
Fuel tank	Not applicable	No fuel tank. The attachment carries no engine or fuel system.
Hydraulic system and tank	Not applicable to the attachment; draws from the host skid steer loader's high-flow hydraulic circuit	No dedicated hydraulic reservoir ships with the PC9. Fluid type and capacity follow the carrier machine's own OMM (high-flow hydraulic oil spec for that loader model), not a PC9-specific chart.
Drum drive gearbox (planetary double-reduction, mounted inside the planer drum)	Not documented in available OMM excerpts for this exact model — verify with your dealer	Sealed gear-drive unit turned by the attachment's hydraulic motor. Where a fill/level check is called out on this attachment family, general-purpose gear oil is used; exact viscosity grade and climate notes were not confirmed for the PC9 specifically and should be checked against the printed OMM carried in the attachment's document case.
Final drives / axles / differentials	Not applicable	No separate final drive or axle assemblies; drive function is integrated into the single drum gearbox listed above.
Grease points (drum bearings, hydraulic cylinder pivots, side-shift wear bars/rods, depth skids)	Grease spec only, no fill capacity — regrease at short intervals per the maintenance schedule (light, frequent applications; wipe off excess to avoid collecting dirt)	General-purpose Cat grease (multipurpose/moly-fortified type used across Cat work tools) at all pivot points, wheel/drum bearings, and wear surfaces. No brand-specific viscosity-by-climate split is published for this attachment; climate-graded selection applies to the carrier machine's own grease and hydraulic oil, not the planer itself.

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Caterpillar PC9 maintenance schedule

Service interval	Tasks
Every 10 h	Inspect all conical bits/picks for wear flats, chipping, or missing carbide tips; rotate or replace as needed Check hydraulic hoses, quick couplers, and O-ring face seals for leaks, abrasion, or loose fittings before start-up Grease the drum dead-shaft bearing zerk at the rear of the housing Clear packed asphalt or concrete spoil from the drum housing, skid shoes, and conveyor/discharge chute Inspect skid shoes and depth-guide wear plates for uneven wear that would throw off cut depth Confirm the skid-steer quick-coupler lock pins are fully engaged before planing
Every 50 h	Check planetary gearbox oil level at the sight/fill plug and top off with the specified gear lubricant Grease depth-adjustment cylinder pivot points on both ends Inspect reversible kicker paddles for wear and flip or replace once one face is worn Torque-check drum housing mounting bolts and coupler frame hardware Inspect the hydraulic drive motor mounting flange and shaft seal for weeping oil
Every 250 h	Change planetary gearbox oil (first change at 100 hours on a new or rebuilt unit, then every 250 hours) Pull and inspect the dead-shaft bearing and seal for play, scoring, or contamination ingress Inspect the full bit holder/block set for cracked blocks or worn retaining clips, replace as a set if wear is uneven Inspect hydraulic hoses end-to-end for cover cracking, cold flow, or heat damage and replace on condition Check drum runout and shell wear; re-face or replace drum if bit blocks no longer seat flush
Every 1,000 h	Remove and tear down the planetary gearbox to inspect gear teeth, planet carrier, and bearings for pitting or wear Replace drum dead-shaft bearing and seals as a set regardless of apparent condition Inspect the axial-piston hydraulic drive motor internally or send out for shop evaluation if flow/speed has degraded Inspect the drum shell and bit-holder weld pads for cracking from cumulative impact loading Replace all hydraulic hoses and O-ring face seals on the work tool circuit as a preventive set

Servicing the PC9 beyond the schedule

Predictive Maintenance & Fluid Analysis

Track planetary gearbox oil condition at each change interval; discoloration, metal fines, or a burnt smell signal early bearing or gear wear inside the drum-mounted gearbox. Sample the carrier's auxiliary hydraulic oil per the host machine's schedule, since drive-motor wear on the PC9 shows up as contamination or viscosity shift in the shared circuit. Watch bit wear rate and drum vibration trend as leading indicators of bearing or gearbox degradation before a failure sidelines the tool.

Corrective & Common Repairs

Most PC9 downtime traces to worn or broken conical bits, cracked bit-holder blocks, and torn drum dead-shaft seals letting spoil into the bearing. Replace bits and holder blocks as soon as flats or cracks appear to prevent uneven drum loading. Leaking O-ring face seals or chafed hoses on the auxiliary circuit are the next most common fix; replace on condition rather than waiting for a burst. Reversible kicker paddles and skid shoes are wear items, not failure points, and should be swapped proactively.

Overhaul & Rebuild Points

A full PC9 rebuild centers on the drum assembly: planetary gearbox teardown, dead-shaft bearing and seal replacement, and drum shell inspection for weld-pad cracking around the bit-holder pockets. The axial-piston hydraulic motor should be bench-tested or rebuilt if flow response has dropped, since it drives gearbox input speed directly. Re-torque or replace the coupler frame and mounting hardware during any major rebuild, as repeated impact loading works these fasteners loose over time.

Seasonal & Environment Servicing

Before cold-weather storage, flush packed asphalt or concrete fines from the drum housing and skid shoes to stop corrosion and seized adjusters. Cap all quick-coupler hydraulic connections to keep moisture and grit out of the circuit during layup. In hot, abrasive milling conditions, shorten bit and bearing-grease inspection intervals, since carbide wear and dead-shaft bearing grease purge both accelerate with heat and fine debris loading.

PC9 attachments & work tools

Work tool type and carriers

PC9 is a rotary-drum cold planer designed as a work tool for Cat skid steer loaders, compact track loaders, compact wheel loaders, and backhoe loaders running a high-flow hydraulic circuit. It belongs to the legacy small cold-planer lineup alongside PC3, PC4, and PC6, with PC9 as the largest, highest-production unit in that group.

Drum width and class

Maximum drum width is 812 mm (32 in), the largest in its family. The high-flow pairing PC6 tops out at 610 mm (24 in); standard-flow siblings PC3 and PC4 run 305 mm (12 in) and 406 mm (16 in) for lighter utility planing, giving context for where PC9 sits in the size class.

Cutting depth and productivity

As a high-flow unit, PC9 is built for production planing beyond 76 mm (3 in) in asphalt and up to about 16 mm (0.63 in) in concrete, versus the standard-flow PC3/PC4 which are limited to utility planing around 51 mm (2 in) asphalt and 10 mm (0.38 in) concrete.

Hydraulic requirement

Requires a high-flow auxiliary circuit; high-flow cold planers in this size class typically draw roughly 100-190 L/min (27-50 GPM) at pressures up to about 31 000 kPa (4500 psi), though exact flow and pressure needed varies by configuration and carrier.

Coupler and mounting

Mounts via the Cat skid steer universal quick-coupler plate for fast pin-on attach/detach, with quick-connect hydraulic couplers for the motor circuit. No separate mounting frame kit is documented beyond the standard carrier quick-attach system.

Drive and tilt/depth control

Uses a direct planetary drive paired with a hydraulic radial piston motor for cutting torque and drum speed. Tilt and depth are hydraulically adjustable from the cab on the high-flow PC6/PC9 pair, unlike the manually adjusted PC3/PC4.

Guarding and safety features

Fitted with pivoting skids to follow grade and side guards/side plates that contain milled spoil and shield the drum area. These are standard features across the high-flow members of this family.

Cutting tools

Uses carbide-tipped conical bits set in the drum, individually replaceable as they wear. Concrete-oriented bit setups are offered for planing concrete surfaces in addition to standard asphalt bits.

Dust/cooling options

An optional water spray system is available to suppress dust and cool the cutting bits during production milling, extending bit life. Water tank capacity varies by configuration; some cold planers in this general size range carry a frame-mounted tank around 160 L (42 gal) with a sight gauge.

Lineup positioning

PC9 and its PC3/PC4/PC6 siblings represent Cat's earlier small cold-planer naming scheme for skid steer carriers. Current Cat cold planer offerings use different model-number series, so PC9 should be treated as a distinct, self-contained family rather than a predecessor tied to those newer numbers.

All PC9 assemblies by section

Every catalogued assembly group for the Caterpillar PC9. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Frame And Body

173-6665 Frame Gp-Cold Planer

02***87	Fitting-Grease; (Universal Joint)	2
14***66	Skid As	2
16***90	Latch	2
17***65	Frame Group-Cold Planer	1

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168-8568 Frame Gp-Cold Planer

02***87	Fitting-Grease; (Universal Joint)	11
03***53	Ring-Retaining	2
14***67	Pin	1
16***89	Spacer; (52.3x63.5x16-mm Thk)(19mm Thk)	1

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173-6664 Frame Gp-Cold Planer

02***87	Fitting-Grease; (Universal Joint)	11
03***53	Ring-Retaining	2
14***67	Pin	1
16***89	Spacer; (52.3x63.5x16-mm Thk)(19mm Thk)	1

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168-8570 Frame Gp-Cold Planer

02***87	Fitting-Grease; (Universal Joint)	2
14***66	Skid As	4
16***90	Latch	2
16***69	Housing As	1

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Hydraulic System

180-3768 Cylinder Gp-Hydraulic

18***68

Cylinder Group-Hydraulic

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168-8566 Cylinder Gp-Hydraulic

16***66	Cylinder Group-Hydraulic	1
16***77	Kit-Seal	1

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147-6781 Cylinder Gp-Hydraulic

00***14	Ring-Retaining; (Internal)	1
14***81	Cylinder Group-Hydraulic	1
16***77	Kit-Seal	1

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168-8563 Cylinder Gp-Hydraulic

16***63

Cylinder Group-Hydraulic

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173-6661 Hydraulic Ar

14***81	Cylinder Group-Hydraulic	1
15***69	Manifold Group-Control; -Sideshift-Tilt-Dept-Sideshift-Tilt-Depth	1
16***63	Cylinder Group-Hydraulic	1
16***64	Lines Group-Connecting	1

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168-8564 Lines Gp-Connecting

14***19	Connector As	2
14***25	Connector As.	16
14***48	Fitting As	2
15***94	Coupler As-Quick Disconnect; (Female)(Quick Disconnect)	1

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173-6662 Lines Gp-Connecting

12***33	Elbow	2
14***17	Adapter, -12 Orb / -16 Orfs	2
14***18	Connector As	2
15***97	Fitting As; (Quick Disconnect, Female)	1

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155-5569 Manifold Gp-Control -Sideshift-Tilt-Dept-Sideshift-Tilt-Depth

11***04	Kit-Seal; (Check Valve)	1
12***57	Valve Group-Check	1
15***69	Manifold Group-Control; -Sideshift-Tilt-Dept-Sideshift-Tilt-Depth	1
15***76	Manifold As	1

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170-8710 Valve Gp-Solenoid

10***02	Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness)	1
15***70	Nut; (1/2-20-2b-Thd)	2
17***09	Cartridge As	1
17***10	Valve Group-Solenoid	1

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170-8708 Valve Gp-Solenoid

10***02	Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness)	1
15***70	Nut; (1/2-20-2b-Thd)	2
17***07	Cartridge As	1
17***08	Valve Group-Solenoid	1

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Service Equipment And Supplies

185-0880 Kit-Roading Plate & Mounting

17***14	Film-Stripe; (Reflective, Red, White)	2
17***42	Guard	2
18***80	Kit-Roading Plate & Mounting	1
18***41	Guard	1

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180-4845 Plate & Film Gp

12***56	Film; (Warning) (No Step) (On Top Of Hood Behind Cab On Each Side) (On Each Fender Flare)	1
15***62	Film-Information; (Tie-Down Location)	2
15***35	Film-Warning; (Crush Hazard, Stay Back)	3
15***36	Film-Warning; (Read Operation Manual)	1

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173-6667 Plate & Film Gp

12***56	Film; (Warning) (No Step) (On Top Of Hood Behind Cab On Each Side) (On Each Fender Flare)	1
15***15	Plate-Identification	1
15***62	Film-Information; (Tie-Down Location)	2
15***35	Film-Warning; (Crush Hazard, Stay Back)	3

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Work Tool Arrangement

173-6658 Cold Planer Ar

15***70	Kit-Connecting Plug; (2-Pin)(Engine Sensor Wiring Harness)	5
16***94	Harness As-Work Tool	1
17***58	Cold Planer Ar	1
17***59	Drive Group-Cold Planer	1

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168-8560 Cold Planer Ar

15***70	Kit-Connecting Plug; (2-Pin)(Engine Sensor Wiring Harness)	5
16***94	Harness As-Work Tool	1
16***60	Cold Planer Ar	1
16***68	Frame Group-Cold Planer	1

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Work Tools

173-6659 Drive Gp-Cold Planer

01***15	Setscrew-Socket; (1/2-13x0.5-In)(1/2 Thd)	2
14***36	Nut; (9/16-18-Thd)	9
15***63	Kit-Seal	1
16***03	Shaft As	1

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173-6666 Drum Gp-Cold Planer

13***78	Bit As-Cutting; (Standard)	70
14***63	Bit As-Cutting; (Concrete)	70
15***55	Stud	4
17***66	Drum Group-Cold Planer	1

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168-8573 Drum Gp-Cold Planer

13***78	Bit As-Cutting; (Standard)	85
14***63	Bit As-Cutting; (Concrete)	85
15***55	Stud	4
16***73	Drum Group-Cold Planer	1

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189-8642 Kit-Water Spray

00***86	Connector-Hose (1/4-18nptf Thd)	1
12***56	Clamp-Hose	1
17***92	Coupling	1
17***49	Tee	5

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Frequently asked questions

What hydraulic flow does the Cat PC9 require from the carrier?

The PC9 needs high-flow hydraulics, roughly 95-125 L/min (25-33 gpm) at 193-345 bar (2800-5000 psi), supplied through the host skid-steer or CTL's auxiliary high-flow circuit.

What is the operating weight of the Cat PC9?

The PC9 weighs approximately 915 kg (2017 lb), the heaviest attachment in Cat's legacy small skid-steer cold-planer family.

What carriers is the Cat PC9 compatible with?

The PC9 mounts via the Cat skid-steer universal quick-coupler and is designed for high-flow-equipped skid-steer loaders and compact track loaders capable of supplying its required hydraulic flow and pressure.

What PC9 owners discuss

What hydraulic behavior should I expect from the PC9's high-flow circuit?

The PC9 draws continuous high-flow charge to the drum motor; running it on a standard-flow carrier starves the circuit, overheats the oil, and accelerates seal, hose, and pump wear. Owners report the drum bogging or stalling in the cut when the carrier's depth or side-shift controls draw flow away from the motor circuit mid-pass - usually a carrier plumbing or valve issue rather than the attachment itself. A restricted case-drain line is a known trigger for a blown motor shaft seal; check case-drain coupler engagement and hose routing at every service interval. Have your dealer verify case-drain flow and shaft seal condition if you see oil weeping at the motor.

What wear patterns show up in the drum motor and gearbox on a PC9?

The planetary gearbox and axial-piston drum motor sit inside the drum housing, using drum inertia to smooth load spikes; this protects the motor but makes gearbox condition hard to judge without pulling the access cover. Wear concentrates at the dead-shaft bearing on the non-motor end of the drum and at the gearbox output seal - look for oil residue at the access door, scorch marks, or a spongy or loose feel when rocking the drum by hand.

How fast do the carbide bits (picks) wear, and how are they replaced?

Owners check picks every one to two hours of cutting and replace any that are broken, flat-spotted, or no longer spinning freely in the holder - a seized pick wears a flat on one side and chews up the holder faster than a pick rotating normally. Running water into the cutting path knocks down dust, flushes debris, and keeps picks turning in their holders. Abrasive material such as concrete or reinforced surfaces calls for heavy-duty or concrete-rated bits instead of standard asphalt picks, and bit life drops noticeably in rock or gravel-contaminated asphalt.

What quirks come up with depth adjustment on the PC9?

Start the drum spinning before it touches the surface, then feed depth in gradually - dropping onto a stopped or slow-turning drum causes the head to bounce and take uneven bites instead of a clean cut. The pivoting skis carry the depth reference over uneven ground; worn or bent skis are a common cause of a wavy cut floor that operators first blame on the drum or picks.

What quirks come up with tilt and side-shift adjustment?

Tilt is meant for feathering cuts at curb lines and around obstacles like manholes, not for general milling - leaving it engaged through a straight run produces an uneven cut depth across the drum width. Side-shift range and feel varies by configuration; check that the shift cylinder and slide rails move freely and aren't packed with cured material, since a sticking slide is a frequent complaint on units left outdoors between jobs.

What issues come up most often when inspecting or buying a used PC9?

Documented used-market experience for this legacy family is thin, and there's no widely reported serial or production-year breakdown to check a unit against, so inspection has to lean on physical condition rather than a paper trail. The recurring complaints match the wider high-flow skid-steer planer class: worn pick holders and flattened mounting bases from repeated bit changes, drum bearing play, gearbox oil residue at the access door, and hose or coupler wear from sustained high-flow duty cycles.

What should I check before buying a used PC9?

Confirm the carrier actually delivers high-flow output matched to the drum motor rating - don't take a seller's word for it. Rock the drum by hand to feel for bearing play, open the access door and look for gearbox oil weeping or metal in the residue, and check pick holders for flattened or elongated mounting points, a sign of repeated re-tightening past normal service life. Check ski wear and straightness, cycle tilt and side-shift through full range for binding, and inspect hoses and the case-drain coupler for cracking or swelling. Have your dealer verify hydraulic flow and pressure output against the drum motor's rating before running it hard.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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