Caterpillar GLS55
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar GLS55 is a shovel-style hydraulic grapple work tool built for log and scrap handling. It has no engine, transmission, or undercarriage of its own — it is a passive attachment that mounts via a heel-boom linkage onto a hydraulic excavator fitted with the heel-boom option, drawing all rotation and clamping force from the host machine's hydraulic circuit through a gerotor-type rotator motor and a pair of grapple cylinders. The GLS55 is the smallest size class in a shared Caterpillar grapple-shovel line that also includes the GLS60, GLS63, and GLS66, scaling up in shell size and reach across the family. It is designed to fit the Cat 320B, 322B/C, 325B/C, or 330B/C excavator once that host carries the heel-boom hydraulic option.
Within that shared family, the GLS55 carries its own serial prefix, distinct from its GLS60, GLS63, and GLS66 siblings, and the grapple cylinder bore and stroke published for it are specific to this size class rather than shared across the whole line. In the used and parts market today the GLS55 is a niche, thinly documented B-series-era attachment: no factory operating weight, overall dimensions, or jaw opening capacity are published for it, and buyers typically confirm those figures from the nameplate on the actual unit rather than a spec sheet. Because the GLS55 shares one parts book and many common components — pins, cylinder hardware, rotator group — with its GLS60/63/66 siblings, parts interchange within the family is common, but the size-specific components (shell, cylinders, some pin lengths) do not cross over and should be matched to the GRC-prefix unit specifically.
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 GLS55 specifications
Weights
| Operating weight | Not published in available documentation for this exact configuration. Varies by GLS55/60/63/66 size class within the shared grapple-shovel line; confirm actual weight on the attachment nameplate or with your dealer. |
Dimensions
| Overall dimensions | Not published in available documentation. The GLS55 is the smallest of the GLS55/60/63/66 grapple-shovel family sharing one parts book; shell width and reach scale up through the GLS66. Confirm exact figures on the attachment nameplate or with your dealer. |
| Shell/jaw opening capacity | Not published in available documentation for this exact model; varies by GLS55/60/63/66 configuration. |
Performance
| Grapple cylinder bore x stroke | 114.3 mm (4.5 in) bore x 193.7 mm (7.6 in) stroke |
| Rotator type | Hydraulic gerotor-type rotator motor; rotates the grapple shell independent of the heel-boom linkage |
| Grapple closing/lift force | Not published in available documentation |
| Hydraulic flow/pressure required from host | Not published as a fixed GLS55 figure. The grapple has no hydraulic system of its own; it draws flow and pressure entirely from the host excavator's auxiliary/work-tool circuit, so available flow and pressure follow the host machine's own hydraulic rating |
| Host machine / mounting | Mounts via a heel-boom linkage on a Cat 320B, 322B/C, 325B/C, or 330B/C hydraulic excavator fitted with the heel-boom option |
Service capacities (summary)
| Hydraulic reservoir | None onboard. The grapple has no tank or pump of its own; it runs entirely off the host excavator's hydraulic oil and circuit |
| Grease points | Heel-boom mounting pins, grapple pivot pins, and cylinder pin ends take grease at standard work-tool service intervals; an exact point count is not published in available documentation |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
GLS55 fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Grapple pivot pins, bushings & rotator bearing (grease points) | No fluid capacity — serviced via grease fittings only, not a fill volume | General Cat work-tool guidance, not a published GLS55-specific spec: multipurpose EP grease such as Cat Prime Application Grease (NLGI 2, 3% moly) for standard conditions, or a 5% moly EP grease for high-load/high-speed pins; regrease at each shift or per the host excavator's grease-point interval. Verify exact interval and grease grade against the OMM for this attachment or your dealer. |
| Hydraulic rotator (Gerotor motor) & grapple cylinders | No onboard reservoir — the GLS55 has no hydraulic tank of its own; it runs on oil supplied by the host excavator's hydraulic circuit | Use the hydraulic fluid specified in the host excavator's own OMM (e.g. the 320B/322B-C/325B-C/330B-C hydraulic system fill); no separate GLS55 hydraulic fluid grade is documented since the tool shares the carrier's oil, not its own. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar GLS55 maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 50 h |
|
| Every 250 h |
|
| Every 1,000 h |
|
Servicing the GLS55 beyond the schedule
Predictive Maintenance & Fluid Analysis
The GLS55 has no engine or onboard reservoir, so there is no oil sample to pull from the tool itself — the rotator motor and grapple cylinders run on the host excavator's hydraulic oil. Track that host oil's condition, since seal wear in the rotator or cylinders shows up as contamination trends in the host's own sampling. Watch for early warning signs at the tool: slower rotation under load points to rotator wear, cylinder drift under a held load points to seal wear, and rising grease consumption at a pin points to bushing wear.
Corrective & Common Repairs
Typical GLS55 repairs center on the wear items that see direct load: reseal grapple cylinders once rod seals weep or the jaw drifts shut under a held grapple load, rebuild or replace the rotator motor when rotation slows or leaks past the shaft seal, and replace worn pins and bushings at the heel-boom and grapple pivot points once clearance exceeds limits. Shell wear plates and tine tips wear from repeated log or scrap contact and are replaced rather than repaired. Chafed hose runs across the heel-boom linkage are a recurring field fix.
Overhaul & Rebuild Points
A full rebuild on the GLS55 centers on the heel-boom linkage and grapple frame pin/bushing set once clearance opens up across multiple joints rather than one. Cylinder overhaul covers seals, wear rings, and rod condition; a scored or out-of-round rod calls for rod work before reseal. Rotator motor rebuild addresses the gerotor set, seals, and bearing once rotation torque drops off. Cracked shell or frame welds are repaired per standard Cat work-tool weld procedure, and linkage joints are re-pinned and shimmed back to original tolerance.
Seasonal & Environment Servicing
In cold weather, switch pin and bushing grease to a low-temperature grade so grease still flows to the fitting at startup instead of packing dry. High-cycle logging or scrap-handling sites accelerate shell and pin wear, so shorten inspection intervals under heavy use rather than running the standard schedule. Because the grapple has no hydraulic system of its own, confirm the host excavator's hydraulic oil viscosity grade matches ambient temperature. In wet or muddy sites, clean grease fittings and pin joints more often so contaminants do not get pumped into the bushings.
GLS55 attachments & work tools
Host excavator compatibility (heel-boom option)
The GLS55 grapple-shovel is built to mount on Caterpillar 320B, 322B/322C, 325B/325C, or 330B/330C hydraulic excavators equipped with the factory heel-boom (log-loader front) option. This host range is documented for the shared parts book covering GLS55, GLS60, GLS63, and GLS66 as a family, so it applies across the whole line rather than being GLS55-exclusive.
Coupler / mounting pin system
The grapple connects to the excavator's heel-boom linkage through a dedicated pin group rather than a universal quick-coupler plate; the pin hardware is documented as its own group separate from the grapple's cylinder-and-lines group in the shared parts manual. This pin-mounting arrangement is common to the GLS55/GLS60/GLS63/GLS66 family and is sized to the host heel-boom linkage rather than being unique to the GLS55.
Hydraulic-kit / plumbing requirements from host excavator
The host excavator needs the heel-boom/log-loader hydraulic circuit already installed (or added) to feed the heel cylinder and grapple cylinders; this is documented as a separate cylinder-and-lines group in the shared GLS55-GLS66 parts manual. Heel-boom/log-loader hosts in this size range can also carry an optional dealer-installed butt-n-top hydraulic circuit for added grapple functions. Exact flow and pressure requirements vary by host excavator model, series, and configuration, so verify against the specific machine's heel-boom hydraulic kit documentation.
Shell / tine / guarding configuration options
No shell, tine, or guarding configuration options specific to the GLS55 by name are documented in available sources. The shared parts book instead differentiates GLS55, GLS60, GLS63, and GLS66 mainly by size/capacity class within one common grapple-shovel design, so any shell or tine variant claims should not be treated as GLS55-specific without direct confirmation.
All GLS55 assemblies by section
Every catalogued assembly group for the Caterpillar GLS55. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Frame And Body
249-1008 Cover Gp-Access
| 24***04 | Plate | 1 |
| 24***23 | Plate | 2 |
| 24***08 | Cover Group-Access | 1 |
249-5124 Cover Gp-Access
| 24***04 | Plate | 1 |
| 24***23 | Plate | 2 |
| 24***15 | Plate As | 2 |
Hydraulic System
249-5099 Cylinder & Lines Gp-Grapple
| 17***03 | Hose As | 4 |
| 24***99 | Cylinder & Lines Group-Grapple | 1 |
| 24***00 | Cylinder Group-Hydraulic; -Grapple | 2 |
249-1006 Cylinder & Lines Gp-Grapple
| 18***78 | Hose As | 4 |
| 24***97 | Cylinder Group-Hydraulic | 2 |
| 24***06 | Cylinder & Lines Group-Grapple | 1 |
249-0997 Cylinder Gp-Hydraulic
| 11***13 | Kit-Seal | 1 |
| 1B***67 | Bolt, Hex. Hd., 5/8"-11 N.C. X 3" | 8 |
| 24***97 | Cylinder Group-Hydraulic | 1 |
249-5100 Cylinder Gp-Hydraulic
| 11***13 | Bolt-Hex Head; (M16x2x70mm) | 6 |
| 16***84 | Kit-Seal | 1 |
| 18***92 | Valve As-Counterbalance | 1 |
261-4654 Motor Gp-Gerotor
| 26***51 | Valve As-Relief; (1500-Psi) | 1 |
| 26***52 | Valve As-Relief; (2000-Psi) | 1 |
| 26***53 | Valve As-Relief; (3000-Psi) | 1 |
249-0172 Rotator Gp-Hydraulic
| 22***82 | Gear & Bearing As | 1 |
| 22***96 | Gear-Pinion; (13-Teeth) | 1 |
| 23***11 | Kit-Seal; (Manifold) | 1 |
Service Equipment And Supplies
249-3151 Film Gp
| 15***35 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
| 15***36 | Film-Warning; (Read Operation Manual) | 2 |
| 24***51 | Film Group | 1 |
249-3153 Film Gp
| 15***35 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
| 15***36 | Film-Warning; (Read Operation Manual) | 2 |
| 24***09 | Film; (Cat, Gls63) | 2 |
249-3154 Film Gp
| 15***35 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
| 15***36 | Film-Warning; (Read Operation Manual) | 2 |
| 24***12 | Film; (Cat, Gls66) | 2 |
249-3152 Film Gp
| 15***35 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
| 15***36 | Film-Warning; (Read Operation Manual) | 2 |
| 24***08 | Film; (Cat, Gls60) | 2 |
Work Tool Arrangement
249-3142 Grapple Ar-Shovel
| 24***94 | Crosshead As | 1 |
| 24***72 | Rotator Group-Hydraulic | 1 |
| 24***38 | Shell Group-Grapple | 1 |
249-3146 Grapple Ar-Shovel
| 24***14 | Housing As | 1 |
| 24***27 | Tube | 4 |
| 24***94 | Crosshead As | 1 |
249-3145 Grapple Ar-Shovel
| 24***14 | Housing As | 1 |
| 24***94 | Crosshead As | 1 |
| 24***76 | Shell As | 1 |
243-5482 Grapple Ar-Shovel -Gls60
| 24***82 | Grapple Ar-Shovel; -Gls60 | 1 |
| 24***43 | Grapple Ar-Shovel | 1 |
249-3143 Grapple Ar-Shovel
| 24***14 | Housing As | 1 |
| 24***27 | Tube | 4 |
| 24***28 | Shell As | 1 |
243-5483 Grapple Ar-Shovel -Gls63
| 24***83 | Grapple Ar-Shovel; -Gls63 | 1 |
| 24***45 | Grapple Ar-Shovel | 1 |
243-5484 Grapple Ar-Shovel -Gls66
| 24***84 | Grapple Ar-Shovel; -Gls66 | 1 |
| 24***46 | Grapple Ar-Shovel | 1 |
243-5481 Grapple Ar-Shovel -Gls55
| 24***81 | Grapple Ar-Shovel; -Gls55 | 1 |
| 24***42 | Grapple Ar-Shovel; -Gls55 | 1 |
Work Tools
249-3155 Fastener Gp-Work Tool
| 09***73 | Bolt; (Socket Head) (M12x1.75x60mm) | 4 |
| 24***55 | Fastener Group-Work Tool | 1 |
| 2L***01 | Bolt; (5/8-18x1.5-In) | 2 |
249-5165 Fastener Gp-Work Tool
| 09***73 | Bolt; (Socket Head) (M12x1.75x60mm) | 4 |
| 24***65 | Fastener Group-Work Tool | 1 |
| 25***30 | Spacer; (16.27x25.4x10.7-mm Thk) | 2 |
249-2901 Pin Gp-Grapple
| 12***13 | Pin-Keeper | 1 |
| 24***92 | Pin As | 2 |
| 24***94 | Plate | 1 |
249-5159 Pin Gp-Grapple
| 24***92 | Pin As | 2 |
| 24***94 | Plate | 1 |
| 24***07 | Plate | 4 |
GLS55 serial number reference
The PIN plate for the GLS55 is mounted on the grapple attachment itself, not on the host excavator, since this is a bolt-on work tool rather than a self-powered machine. The plate shows a 3-letter model prefix followed by a sequential unit number; GRC is the prefix that identifies the attachment specifically as a GLS55 within the shared GLS55/GLS60/GLS63/GLS66 forestry-grapple catalog family. Confirm the full plate reading against the parts catalog if the attachment could be a rebadged or reworked unit, since these grapples were also field-fitted to 320B, 322B/C, 325B/C and 330B/C excavators with the heel-boom option.
| Prefix | Identifies | Notes |
|---|---|---|
| GRC | GLS55 grapple-shovel attachment (base/only known production run) | GRC1-UP is the sole PIN prefix documented for the GLS55 in the shared forestry-grapple parts book that also covers the GLS60, GLS63 and GLS66. It appears against GLS55-specific grapple-arm and hydraulic cylinder/line group listings, distinct from the GLS60, GLS63 and GLS66 siblings in the same document set. No second or later GLS55 prefix turned up; no publicized production-year window is tied to this range. |
Frequently asked questions
What excavators does the Cat GLS55 grapple fit?
The GLS55 mounts on a Cat 320B, 322B/C, 325B/C, or 330B/C hydraulic excavator fitted with the heel-boom option. It attaches through a dedicated pin group rather than a universal quick coupler, so the host machine needs the matching heel-boom linkage and grapple hydraulic circuit already installed.
Does the GLS55 have its own hydraulic system?
No. The grapple carries no pump, reservoir, or filtration of its own. Its rotator motor and grapple cylinders run entirely off the host excavator's auxiliary work-tool hydraulic circuit, so fluid type, cleanliness, and pressure follow whatever the host machine's own operation and maintenance manual specifies.
What size are the GLS55 grapple cylinders?
The confirmed grapple cylinder on the GLS55 is 114.3 mm (4.5 in) bore by 193.7 mm (7.6 in) stroke. Overall grapple weight, jaw opening capacity, and outside dimensions are not published for this size class; check the attachment nameplate on the actual unit or ask your dealer for exact figures.
What GLS55 owners discuss
How long do the rotator and grapple cylinders typically last before needing seal work?
What are the main wear points and how often should they be greased?
Do the jaws and shells wear evenly, or is there a known pattern?
Any quirks with hose routing or fitment on the heel-boom mount?
Does the host excavator's hydraulic flow and pressure need to match the grapple?
What should I check before buying a used one?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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