Caterpillar SR321
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar SR321 is a hydraulically-driven snow blower work tool, not a self-propelled machine. It has no engine, transmission, or onboard hydraulic reservoir; its auger and impeller gerotor motors and lift cylinder draw power entirely from the host carrier's high-flow auxiliary hydraulic circuit. At 1,942 mm (76.5 in) intake width and 2,181 mm (85.9 in) overall, the SR321 sits in the 85 in size class of Caterpillar's SR-series lineup, above the narrower SR115, SR118/SR318, and SR121, and below the larger SR418/SR421. Operating weight runs 461-527 kg (1,016-1,162 lb), varying by configuration. It mounts to Cat compact wheel loaders (906-908), skid steer loaders (236D3-272D3), and compact track loaders (239D3-299D3) equipped with High-Flow XPS/XHP/XE hydraulics delivering 100-125 L/min at 200-280 bar, and remains Caterpillar's current 85 in-class hydraulic snow blower attachment.
Serial-prefix production records place the SR321 in continuous manufacture from the mid-2000s (SWX prefix) and earlier (BLZ prefix, early-2000s) through current KZB-prefix production. The attachment uses a relief valve for overload protection rather than a mechanical shear pin, guarding the auger and impeller drivetrain from ice and debris impacts without a wear part to replace after every overload event. That long, unbroken production run means active OEM parts support and wide availability on municipal, rental, and contractor fleets running Cat skid steers, compact track loaders, and compact wheel loaders through winter service. Buyers in the used and parts market benefit from a stable design with no documented generation break to complicate parts interchange.
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 SR321 specifications
Weights
| Operating weight | 461–527 kg (1,016–1,162 lb); figure varies across published spec sheets for this unit |
Dimensions
| Overall length | 951 mm (37.4 in) |
| Overall width (transport) | 2,181 mm (85.9 in) |
| Overall height | 1,843 mm (72.6 in) |
| Cutting/intake width | 1,942 mm (76.5 in) intake opening. SR321 is Cat's 85 in-class snow blower in the SR-series lineup; the 67 in and 73 in width classes are separate model numbers (SR117; SR118/SR318), not SR321 configurations. |
| Auger diameter | 457 mm (18 in), serrated flighting to break up hard-packed snow and ice |
| Impeller (fan) diameter | 635 mm (25 in) |
| Impeller (fan) width | 222 mm (8.7 in) |
| Maximum cutting height (snow depth per pass) | 867 mm (34.1 in) |
Performance
| Hydraulic flow required (from host carrier) | 100–125 L/min (26–33 gpm); optimal 125 L/min (33 gpm) on the High-Flow XPS auxiliary circuit |
| Hydraulic pressure required (from host carrier) | 200–280 bar (2,900–4,060 psi); optimal 280 bar (4,061 psi) |
| Maximum throw distance | 12.2 m (40 ft) |
| Chute rotation range | 270 degrees; discharges to front or either side to keep blown snow off the operator |
| Auger/impeller direction | Both auger and impeller reverse from the cab to clear obstructions without leaving the seat |
| Host carrier compatibility | Mounts to Cat compact wheel loaders (906, 907, 908), skid steer loaders (236D3, 242D3, 246D3, 262D3, 272D3), and compact track loaders (239D3, 249D3, 259D3, 279D3, 289D3, 299D3) fitted with High-Flow XPS hydraulics. Quick-coupler height adjusts to three positions to match carrier type and configuration. |
Service capacities (summary)
| Hydraulic system | No onboard reservoir; draws entirely from the host carrier's auxiliary hydraulic circuit. Requires High-Flow XPS: 100–125 L/min (26–33 gpm) at 200–280 bar (2,900–4,060 psi), optimal 125 L/min (33 gpm) at 280 bar (4,061 psi). |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
SR321 fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Grease points (pivot pins, hitch mount, work tool linkage) | grease point — no fill capacity | Not documented in publicly available sources for this work tool. This attachment has no engine, transmission, fuel tank, coolant system, or hydraulic reservoir of its own; its auger and impeller run off gerotor motors and a lift cylinder supplied by the host carrier's hydraulic circuit. The Caterpillar operation and maintenance manual for the SR-series snowblowers includes a Maintenance Interval Schedule section covering lubrication points for this unit; consult that manual or a Cat dealer for the exact grease name and service interval. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar SR321 maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 50 h |
|
| Every 250 h |
|
| Every 500 h |
|
Servicing the SR321 beyond the schedule
Predictive maintenance & fluid analysis
The SR321 has no reservoir of its own; hydraulic-circuit health depends on the host carrier's hydraulic oil, not any onboard fluid schedule. Watch the auger and impeller gerotor motor shaft seals for early weeping, a sign of internal wear before a motor fails outright. Track the host machine's hydraulic oil condition and cleanliness, since contamination there feeds directly into the attachment's motors and cylinder. Inspect hoses and fittings regularly for trending wear rather than waiting for a failure.
Corrective & common repairs
Common SR321 repairs center on wear parts that take the brunt of snow and ice contact: auger and impeller flighting, blades, cutting edge, and skid shoes all see regular replacement in heavy seasonal use. Hydraulic hoses and quick-couplers are frequent repair points, since they see constant connect/disconnect cycling and exposure to road salt and grit. When the auger or impeller loses power or stalls under light loads, relief valve troubleshooting is the first check before assuming a motor fault.
Overhaul & rebuild points
Deeper overhaul work on the SR321 centers on the auger and impeller gerotor drive motors: seal kits address shaft weeping before it becomes a full motor rebuild or replacement. Auger and impeller bearings wear over long service and should be checked for play or roughness during major inspections. The frame, hitch mount, and linkage pins and bushings also take cumulative wear from vibration and lift-cylinder cycling, and loose pins or elongated bushing bores are common findings on high-hour units headed for rebuild.
Seasonal & environment servicing
Pre-season prep on the SR321 means a full grease pass on every pivot and hitch point plus a hose and fitting inspection before the first storm. Wet, heavy snow can pack and clog the chute and deflector, so operators should plan for regular clearing during use in warmer, wetter conditions. Cold weather stiffens coupler seals and O-rings, so a slow, deliberate hookup helps prevent damage. For off-season storage, relieve hydraulic pressure in the circuit and protect any exposed cylinder rod from corrosion and pitting.
SR321 attachments & work tools
Mounting / coupler system
The SR321 attaches through a quick-coupler plate on its back frame, the same interface used by the carrier's other work tools. The coupler is adjustable to three different heights so the blower lines up correctly across different carrier frames and configurations. Chute, auger, impeller and deflector run off the carrier's own hydraulics, and the carrier's factory joysticks control chute rotation and deflector with no extra wiring or valve kit to install.
Host carrier compatibility
Cat factory literature lists the SR321 for D/D3-series skid steer loaders, compact track loaders and multi-terrain loaders in the 226-299 size range, plus 906K/M, 907K/M and 908K/M compact wheel loaders. It needs the carrier's high-flow hydraulic package and the high-flow XPS option; on XHP/XE compact wheel loader models it runs directly on the standard high-flow XPS circuit. No motor grader or other carrier class is documented for this tool.
Cutting-width configuration
As built, the SR321 is a single fixed-width unit: about 1942 mm (76.5 in) intake and 2181 mm (85.9 in) overall width, the widest blower in the Cat SR-series lineup (SR115 runs 1290 mm/51 in intake, SR118 and SR318 run 1614 mm/63.5 in, SR121 shares the SR321's 1942 mm/76.5 in intake). A separate 67 in SR321 width figure turned up in one search summary but is not backed by Cat or dealer spec sheets, so treat it as unconfirmed rather than a real configuration.
Factory guarding / kit options
An optional truck chute kit adds a folding dual-chute section for extra throw height and distance when loading trucks. An optional performance package adds a non-metallic chute liner, side drift cutters, an impeller ingestion plate and a chute cover plate to cut down on plugging and spillback. Adjustable skid shoes and a bolt-on, reversible cutting edge handle wear control; no dedicated cab guard is documented for this model.
All SR321 assemblies by section
Every catalogued assembly group for the Caterpillar SR321. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Electrical System
281-3790 Wiring Gp-Work Tool
| 10***67 | Washer-Hard; (7.2x25x2-mm Thk) | 2 |
| 11***15 | Relay As; (12-Volt)(Junction Box) | 2 |
| 12***78 | Locknut; (M6x1-Thd) | 4 |
261-4419 Wiring Gp-Work Tool
| 10***67 | Washer-Hard; (7.2x25x2-mm Thk) | 2 |
| 10***02 | Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness) | 3 |
| 11***15 | Relay As; (12-Volt)(Junction Box) | 2 |
Frame And Body
290-8925 Deflector Gp-Snowblower
| 03***55 | Locknut; (5/16-18-Thd)(Marked X) | 6 |
| 12***78 | Locknut; (M6x1-Thd) | 2 |
| 13***85 | Rivet-Pop | 7 |
290-8888 Deflector Gp-Snowblower
| 03***55 | Locknut; (5/16-18-Thd)(Marked X) | 6 |
| 12***78 | Locknut; (M6x1-Thd) | 2 |
| 13***85 | Rivet-Pop | 7 |
290-8919 Frame Gp-Snowblower
| 1K***72 | Locknut Horn To Guard | 9 |
| 21***75 | Frame As | 1 |
| 21***80 | Impeller As | 1 |
290-8924 Frame Gp-Snowblower
| 1K***72 | Locknut Horn To Guard | 7 |
| 21***82 | Impeller As | 1 |
| 21***83 | Guard As | 1 |
290-8915 Frame Gp-Snowblower
| 1K***72 | Locknut Horn To Guard | 8 |
| 21***22 | Support Group-Work Tool | 2 |
| 21***23 | Frame As | 1 |
213-7222 Support Gp-Work Tool
| 21***22 | Support Group-Work Tool | 1 |
| 28***93 | Tube As | 1 |
| 28***97 | Pad As; (Stabilizer) | 1 |
Hydraulic System
283-9595 Cylinder Gp-Hydraulic
| 28***95 | Cylinder Group-Hydraulic | 1 |
| 4K***77 | Nut-Self Locking | 1 |
| 7J***04 | Seal-O-Ring (Id=7.65mm) | 2 |
295-4866 Hydraulic Ar-Snowblower
| 28***95 | Cylinder Group-Hydraulic | 1 |
| 29***97 | Manifold Group-Control | 1 |
| 29***66 | Hydraulic Ar-Snowblower | 1 |
290-8920 Hydraulic Ar-Snowblower
| 28***95 | Cylinder Group-Hydraulic | 1 |
| 29***20 | Hydraulic Ar-Snowblower | 1 |
| 29***97 | Manifold Group-Control | 1 |
290-8926 Hydraulic Ar-Snowblower
| 28***95 | Cylinder Group-Hydraulic | 1 |
| 29***26 | Hydraulic Ar-Snowblower | 1 |
| 29***97 | Manifold Group-Control | 1 |
290-8916 Hydraulic Ar-Snowblower
| 28***95 | Cylinder Group-Hydraulic | 1 |
| 29***16 | Hydraulic Ar-Snowblower | 1 |
| 29***97 | Manifold Group-Control | 1 |
295-4867 Hydraulic Ar-Snowblower
| 28***95 | Cylinder Group-Hydraulic | 1 |
| 29***97 | Manifold Group-Control | 1 |
| 29***67 | Hydraulic Ar-Snowblower | 1 |
295-4872 Lines Gp-Connecting
| 10***03 | Plate-Cover | 1 |
| 14***48 | Fitting As; (Quick Disconnect, Male) | 1 |
| 14***49 | Fitting As; (Quick Disconnect, Female) | 1 |
295-4870 Lines Gp-Connecting
| 10***03 | Plate-Cover | 1 |
| 14***15 | Connector As | 4 |
| 14***36 | Adapter; (Straight) (-6 Orb X -6 Orfs) | 2 |
295-4871 Lines Gp-Connecting
| 10***03 | Plate-Cover | 1 |
| 14***48 | Fitting As; (Quick Disconnect, Male) | 1 |
| 14***49 | Fitting As; (Quick Disconnect, Female) | 1 |
295-4868 Lines Gp-Connecting
| 10***03 | Plate-Cover | 1 |
| 14***15 | Connector As | 4 |
| 14***36 | Adapter; (Straight) (-6 Orb X -6 Orfs) | 2 |
295-4869 Lines Gp-Connecting
| 10***03 | Plate-Cover | 1 |
| 14***15 | Connector As | 4 |
| 14***36 | Adapter; (Straight) (-6 Orb X -6 Orfs) | 2 |
295-2597 Manifold Gp-Control
| 10***08 | Kit-Seal; (Solenoid Valve, Quick Steer) | 1 |
| 19***27 | Kit-Seal; (Pressure Reducing Valve) | 1 |
| 19***95 | Valve Group-Solenoid; (Swing/Extension) | 2 |
216-0795 Motor Gp-Gerotor
| 17***46 | Kit-Seal | 1 |
| 21***95 | Motor Group-Gerotor | 1 |
| 22***72 | Key | 1 |
212-4587 Motor Gp-Gerotor -Deflector
| 1B***14 | Key-Woodruff | 1 |
| 1G***32 | Kit-Seal | 1 |
| 21***87 | Motor Group-Gerotor; -Deflector | 1 |
212-4588 Motor Gp-Gerotor -Auger, 67-In
| 17***46 | Kit-Seal | 1 |
| 21***88 | Motor Group-Gerotor; -Auger, 67-In | 1 |
213-7192 Motor Gp-Gerotor
| 17***46 | Kit-Seal | 1 |
| 21***92 | Motor Group-Gerotor | 1 |
| 22***72 | Key | 1 |
227-5496 Motor Gp-Gerotor
| 17***46 | Kit-Seal | 1 |
| 22***96 | Motor Group-Gerotor | 1 |
| 3J***54 | Packing,Preformed Part Of Kit P/N 5r***27 | 1 |
212-4589 Motor Gp-Gerotor
| 17***46 | Kit-Seal | 1 |
| 21***89 | Motor Group-Gerotor | 1 |
| 22***72 | Key | 1 |
227-5510 Motor Gp-Gerotor
| 17***46 | Kit-Seal | 1 |
| 22***10 | Motor Group-Gerotor | 1 |
179-9223 Valve Gp-Check
| 17***23 | Valve Group-Check; -Steering Pump | 1 |
| 3J***07 | Seal Valve Assembly To; Seal- Tube Assembly To Logic Valve | 1 |
| 4J***77 | Seal - O - Ring (11.23mm Od) | 1 |
Service Equipment And Supplies
290-8917 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 |
| 22***45 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
261-4423 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 |
| 22***45 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
290-8927 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 |
| 22***45 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
290-8921 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 |
| 22***45 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
261-4426 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 |
| 22***45 | Film-Warning; (Crush Hazard, Stay Back) | 2 |
Work Tool Arrangement
286-0724 Snowblower Ar -67-In
| 28***90 | Bracket, Wiring Group-Work Tool | 1 |
| 28***24 | Snowblower Ar; -67-In | 1 |
| 29***23 | Drive Group-Snowblower | 1 |
286-0726 Snowblower Ar -85-In
| 28***90 | Bracket, Wiring Group-Work Tool | 1 |
| 28***26 | Snowblower Ar; -85-In | 1 |
| 29***18 | Drive Group-Snowblower | 1 |
286-0725 Snowblower Ar -73-In
| 28***90 | Bracket, Wiring Group-Work Tool | 1 |
| 28***25 | Snowblower Ar; -73-In | 1 |
| 29***14 | Drive Group-Snowblower | 1 |
286-0727 Snowblower Ar -73-In
| 26***19 | Wiring Group-Work Tool | 1 |
| 26***23 | Plate & Film Group | 1 |
| 28***27 | Snowblower Ar; -73-In | 1 |
286-0728 Snowblower Ar -85-In
| 26***19 | Wiring Group-Work Tool | 1 |
| 26***26 | Plate & Film Group | 1 |
| 28***28 | Snowblower Ar; -85-In | 1 |
Work Tools
290-8923 Drive Gp-Snowblower
| 01***41 | Setscrew-Socket | 2 |
| 02***87 | Fitting-Grease; (Universal Joint) | 2 |
| 21***44 | Sprocket Group; (16-Teeth, Impeller) | 1 |
290-8918 Drive Gp-Snowblower
| 01***41 | Setscrew-Socket | 2 |
| 02***87 | Fitting-Grease; (Universal Joint) | 2 |
| 21***44 | Sprocket Group; (16-Teeth, Impeller) | 1 |
290-8914 Drive Gp-Snowblower
| 01***41 | Setscrew-Socket | 2 |
| 02***87 | Fitting-Grease; (Universal Joint) | 2 |
| 21***44 | Sprocket Group; (16-Teeth, Impeller) | 1 |
294-7388 Drive Gp-Snowblower
| 01***41 | Setscrew-Socket | 2 |
| 02***87 | Fitting-Grease; (Universal Joint) | 2 |
| 21***44 | Sprocket Group; (16-Teeth, Impeller) | 1 |
SR321 serial number reference
On a hydraulically-driven, pin-mount snowblower like this, the work-tool identification plate is riveted or bolted to the main frame or gearbox housing, usually near the mount/quick-coupler end where it stays visible when the tool is parked or racked. The plate is stamped with the Cat model designation and Product Identification Number: the first three letters are the serial-number prefix identifying the specific build/production run, followed by the sequential unit number. Match that prefix against the parts manual's "S/N X1-Up" break points to pull the correct drive, wiring, and hydraulic assemblies for that unit.
| Prefix | Identifies | Notes |
|---|---|---|
| BLZ | SR321 work tool, early production run (mid-2000s) | Appears as the dedicated serial-range folder under the SR321 model heading in the shared Cat parts catalog covering the SR115, SR118, SR121, SR318 and SR321 snowblower family. Precedes the SWX range chronologically. Single-source - confirm with dealer before ordering against this range. |
| SWX | SR321 work tool, mid-2000s production run | Shown as the S/N 1-Up range for the SR321 model in the shared Cat parts/service manual covering the SR115, SR118, SR121, SR318 and SR321 snowblower family, and is the subject of a dedicated SR321 service and repair manual carrying this same range designation. |
| KZB | SR321 work tool, current production run | Listed as the SR321 serial range in the current Cat operator's manual covering the SR115, SR118, SR121, SR318, SR321, SR418 and SR421 snowblower lineup. Matches a field-sold 2022-model-year SR321 unit carrying a serial number in this range. |
Frequently asked questions
What powers the Caterpillar SR321's auger and impeller?
The SR321 has no engine of its own. Its auger and impeller are driven by gerotor hydraulic motors powered entirely by the host carrier's auxiliary hydraulic circuit, drawing 100-125 L/min at 200-280 bar through a High-Flow XPS/XHP/XE hydraulic system.
What does the Caterpillar SR321 weigh?
Operating weight runs 461-527 kg (1,016-1,162 lb), varying by configuration and source. The attachment has no engine, transmission, or onboard hydraulic reservoir, so its weight reflects only the frame, auger and impeller assembly, chute, and drive motors.
Has the Caterpillar SR321 been replaced by a newer model?
No. Serial-prefix production records show the SR321 in current production under the KZB prefix, following earlier SWX and BLZ blocks. There is no documented successor model; the SR321 remains Caterpillar's current 85 in-class hydraulic snow blower work tool.
What SR321 owners discuss
Can I run the SR321 on a standard-flow skid steer or compact track loader, or does it really need high flow?
What actually wears out first on the auger and impeller hydraulic motors?
Does the SR321 use a shear pin like a homeowner snowblower does?
How does the chute and deflector work, and why does the blower clog in wet snow?
The hydraulic quick couplers will not seat when hooking up the blower - what is wrong?
Does the same SR321 mounting setup fit across wheel loaders, skid steers, and track loaders?
What should I check before buying a used SR321?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific SR321 part?
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