Caterpillartrack-type loaderbulldozer
Caterpillar 977A
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar 977A is a vintage track-type loader (Traxcavator) produced during the mid-1950s through the 1960s. Built on a chassis sharing architecture with the D6 crawler tractor, this machine was offered in a single standard configuration without dozer blade or LGP options. Early production units (20A serial prefix) utilized the D318 6-cylinder naturally aspirated diesel engine, rated at approximately 75 kW (100 hp) at 1,800 rpm, and featured hand-lever steering clutches with foot brakes. Later 53A-prefix series introduced engine progression toward the D333 diesel and transitioned to pedal steering around 1964.
Across its production generations, the 977 series underwent significant mechanical evolution, including shifts from manual levers to pedal steering and changes in engine output. While later lettered models like the 977H or 977L moved into much higher horsepower classes with turbocharged engines and powershift transmissions, the original 977A remains a purely mechanical machine without electronic controls or ECM. Today, this machine is highly valued in the collector and vintage equipment markets. Maintenance focus has shifted from active fleet service to preservation, with parts demand driven by hobbyists and heritage-equipment specialists using NOS (New Old Stock) and salvage components.
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 977A specifications
Engine
| Model (20A-prefix) | D318, 6-cylinder diesel, naturally aspirated, liquid-cooled |
| Displacement (20A-prefix) | 8.6 L (524 cu in) |
| Rated Power (20A-prefix) | 100 hp (75 kW) at 1,800 rpm (gross) |
| Engine progression (53A-prefix) | D318, then D333 diesel, later turbocharged D333T |
| Emissions | Pre-emissions-regulation mechanical diesel; no EPA/Tier certification applicable |
Weights
| Operating Weight (20A-prefix) | 15,900 kg (34,980 lb) |
| Operating Weight (General aggregator range) | 13,230–15,880 kg (29,165–35,000 lb) — varies by source/serial range |
Dimensions
| Overall Length (bare machine) | 5.15 m (162 in / 13 ft 6 in) |
| Overall Length (with bucket) | 5.70 m (222 in / 18 ft 6 in) |
| Overall Width (bare machine) | 2.45 m (95 in / 7 ft 11 in) |
| Overall Width (with bucket) | 2.80 m (109 in / 9 ft 1 in) |
| Overall Height | 2.30 m (90 in / 7 ft 6 in) |
Performance
| Transmission (early production) | 5-speed gearbox with 2-speed transfer case, direct drive, hand-clutch and sliding-gear engagement |
| Steering/Braking Change | Switched from hand-lever steering clutches and foot brakes to pedal steering at unit 53A4797 (circa 1964) |
Blades & Attachments
| Configuration Note | Cataloged strictly as a loader; no dozer blade option documented under the plain 977 name |
| Hydraulic Control (attachment) | Double Valve—50 U.S. Gallons Per Minute for operating No. 6 Ripper and front mounted attachment |
Service Capacities
| Fuel Tank (20A1-up) | 227 L (50 US gal) |
| Engine Oil Capacity | Not confirmed in publicly accessible sources for this serial range; verify against machine OMM |
| Hydraulic System Capacity | Not confirmed in publicly accessible sources for this serial range; verify against machine OMM |
| Cooling System Capacity | Not confirmed in publicly accessible sources for this serial range; verify against machine OMM |
Fluid Specifications
| Engine Oil (D318) | Diesel engine oil selected by ambient temperature per era Cat lubrication chart |
| Fuel | Diesel fuel; machine also uses small gasoline supply for auxiliary pony motor |
| Hydraulic System (General Traxcavator recommendation) | Cat HYDO-type hydraulic oil |
| Final Drives | SAE 50 powertrain oil meeting Cat TO-4 / TDTO specification |
| Grease | Cat Multipurpose Grease (NLGI-graded chassis grease) |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
977A fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (w/ filter) | Not confirmed for SN 20A1-up or 53A1-up | Diesel engine oil selected by ambient temperature per era Cat lubrication chart; use viscosity-by-temperature guidance from OMM rather than generic modern spec. Heavier grade for warm climates, lighter multigrade for cold-start conditions. |
| Cooling system | Not confirmed in publicly accessible sources | Water/antifreeze (ethylene-glycol base) with corrosion inhibitor; confirm concentration against dealer OMM. |
| Fuel tank | 227 L (50 US gal) for SN 20A1-up | Diesel fuel. Note: Auxiliary gasoline pony motor uses separate small gasoline supply. |
| Transmission/powertrain (gearbox & transfer case, SN 20A1-up) | Not confirmed in publicly accessible sources | Treat as transmission/drive-train oil (TDTO-type) pending confirmation against OMM. |
| Transmission & bevel gear/steering compartment (later production, powershift-equipped) | Not confirmed for this model's serial range | Engine-oil-grade SAE 30 (or Cat TDTO-equivalent); reference drawn from later-generation Traxcavator OMM and flagged as cross-generation reference only. |
| Final drives (each) | Not confirmed; drain capacity estimated at a few US gallons per side based on similar-era Cat crawler final drives | SAE 50 powertrain oil meeting Cat TO-4 / TDTO specification. Do not use straight gear oil (GO) as additive package may attack seals. |
| Hydraulic system/tank | Not confirmed in publicly accessible sources | Cat HYDO-type hydraulic oil; confirm against OMM for exact serial range. |
| Grease (chassis/pins/pivots) | No single reservoir capacity applies; service per grease-fitting interval in OMM lubrication chart | Cat Multipurpose Grease (NLGI-graded chassis grease) at pin, pivot, and linkage fittings. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar 977A maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
Servicing the 977A beyond the schedule
Predictive Maintenance & Fluid Analysis
Because the 977A lacks an ECM, oil sampling carries the primary diagnostic load. Perform engine oil analysis at every change interval to monitor for coolant intrusion in wet-liner blocks and detect wear metals. Monitor transmission and final drive oil for metal content, which signals gear or bearing degradation. Use S.O.S-style monitoring of hydraulic fluid to check particle counts and oxidation levels, ensuring the mechanical powertrain remains protected from internal contamination.
Corrective & Common Repairs
Frequent repair points include steering clutch and brake band assemblies, which require periodic relining or full rebuild due to torque routing through these components. On early units, inspect the lever-operated dry steering clutches and mechanical brakes for wear. Additionally, monitor loader lift and tilt cylinders; these often require resealing and rod resurfacing after long service life. For 20A-prefix models, maintain the gasoline pony motor to ensure reliable cold starting and intake-air preheating.
Overhaul & Rebuild Points
Major overhaul milestones include a teardown inspection of the 5-speed gearbox, transfer case, and final drives at high operating hours. The steering clutch compartment and differential require oil changes and seal inspections to prevent leaks. When rebuilding the powertrain, verify all components meet factory tolerances for the specific serial range. Structural inspections should focus on the chassis and pivot points, ensuring that any heavy wear in the undercarriage or linkage is addressed during major component evaluations.
Seasonal & Environment Servicing
In dusty or quarry environments, increase air cleaner service frequency; check the precleaner cup daily and replace elements more often than standard intervals. For cold-start conditions, ensure the gasoline pony motor is functional and the fuel system is free of water/sediment. In high-temperature operations, monitor radiator fin cleanliness to prevent overheating. Always verify that engine oil viscosity matches ambient temperature requirements as specified in the original lubrication charts.
977A common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 9F-6428 | Oil Filter Assembly | Lubrication service | Check fitment → |
| 1H-6517 | Transfer | Lubrication service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
977A attachments & work tools
Blades
Pusher-style blades are available for front or rear mounting on some units. Specific widths and capacities for S, SU, A, or VPAT configurations are not documented for this specific model.
Rippers
Multi-shank rear rippers are documented across 977H, 977K, and 977L generations. These are mounted on the drawbar and operated via the rear hydraulic circuit.
Winches
Winch options with an arch for logging or pulling applications have been used in historical configurations.
Drawbars/counterweights
Counterweights are present on the rear of the machine and may cover steering clutch serial number tags. Trunnion groups are available for mounting 977A bulldozers (Serial No. 43D1 to 43D230).
Cab/ROPS guarding options
Open ROPS configurations are documented. Specific forestry or waste-specific guarding details for the 977A are not explicitly listed.
Hydraulic arrangement notes
Double valve arrangements provide 378.5 L (50 U.S. Gallons Per Minute) for operating No. 6 rippers and front-mounted attachments. Hydraulic systems may utilize 10W hydraulic oil or Cat HYDO Advanced oils.
All 977A assemblies by section
Every catalogued assembly group for the Caterpillar 977A. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Attachments
6h9166 Battery And Wiring Group--24 Volt--Type 2
| 6H***66 | Battery And Wiring Group | 1 |
6h9166 Battery And Wiring Group--24 Volt--Type 1
| 6H***66 | Battery And Wiring Group | 1 |
2k7678 Bucket And Support Group--2 1/4 Cu. Yd.--111" Wide
| 2K***78 | Bucket And Support Group | 1 |
2k7678 Bucket And Support Group--2.25 Cubic Yard--111" Wide--Second Type
| 2K***78 | Bucket And Support Group | 1 |
4k9100 Bucket Assembly--3 Cubic Yard--96" Wide--Replaces 3k9580
| 4K***00 | Bucket Assembly | 1 |
2k4869 Bucket Assembly--1.8 Cu. Yd.--77 1/2" Wide
| 2K***69 | Bucket Assembly | 1 |
2k4812 Bucket Assembly--2 7/8 Cubic Yard--96" Wide
| 2K***12 | Bucket Assembly | 1 |
3k9580 Bucket Assembly--3 Cubic Yard--96" Wide
| 3K***80 | Bucket Assembly | 1 |
2k4827 Bucket Group--2.25 Cubic Yard--96" Wide
| 2K***27 | Bucket Group | 1 |
2k4828 Bucket Group--2.25 Cubic Yard--96" Wide
| 2K***28 | Bucket Group | 1 |
2k2623 Bucket Tooth Group
| 2K***23 | Bucket Tooth Group | 1 |
3k9322 Carriage And Clamp Group
| 3K***22 | Carriage And Clamp Group | 1 |
2k7291 Carriage And Clamp Group
| 2K***91 | Carriage And Clamp Group | 1 |
1k8365 Carriage And Clamp Group--Type 2
| 1K***65 | Carriage And Clamp Group | 1 |
1k8365 Carriage And Clamp Group--Type 1
| 1K***65 | Carriage And Clamp Group | 1 |
7f2921 Combination Switch
| 7F***21 | Combination Switch | 1 |
2k2936 Control Valve Assembly
| 2K***36 | Control Valve Assembly | 1 |
2k6248 Control Valve Assembly
| 2K***48 | Control Valve Assembly | 1 |
7h2157 Covers Group
| 7H***57 | Cover Group | 1 |
5h9204 Crankcase Guard Group--Rear Section
| 5H***04 | Crankcase Guard Group | 1 |
2k8123 Cylinder Group--5 1/2" X 38 15/32"
| 2K***23 | Cylinder Group | 1 |
3k9744 Cylinder Group--L.H.--4.5" Bore X 14" Stroke--Type 2
| 3K***44 | Cylinder Group | 1 |
2k6841 Cylinder Group--4" Bore X 18.625" Stroke
| 2K***41 | Cylinder Group | 1 |
2k6276 Cylinder Group--4.5" Bore X 18.625" Stroke - Type 2
| 2K***76 | Cylinder Group | 1 |
3k9744 Cylinder Group--L.H.--4.5" Bore X 14" Stroke--Type 1
| 3K***44 | Cylinder Group | 1 |
3k9743 Cylinder Group--R.H.--4.5" Bore X 14" Stroke--Type 2
| 3K***43 | Cylinder Group | 1 |
3k9743 Cylinder Group--R.H.--4.5" Bore X 14" Stroke--Type 1
| 3K***43 | Cylinder Group | 1 |
2k7557 Cylinder Group--4 1/2" X 14"
| 2K***57 | Cylinder Group | 1 |
2k6276 Cylinder Group--18 5/8" X 4 1/2" - Type 1
| 2K***76 | Cylinder Group | 1 |
1k8206 Cylinder Group--5" X 13 31/32"
| 1K***06 | Cylinder Group | 1 |
3k481 Cylinder Group--R.H.--5 1/2" X 14"
| 3K***81 | Cylinder Group--R.H.,Cylinder Group--L.H.; Cylinder Group-- R.H. | 1 |
9h6333 Dash Lamp Assembly--6 Volt
| 9H***33 | Dash Lamp Assembly | 1 |
4h5678 Dash Lamp Assembly--24 Volt
| 4H***78 | Dash Lamp Assembly | 1 |
1f7164 Dash Lamp Assembly--6 Volt
| 1F***64 | Dash Lamp Assembly | 1 |
2m2095 Direct Electric Starting Arrangement--24 Volt
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 2 |
| 1H***56 | Wrench--Glow Plug; Wrench- Glow Plug | 1 |
| 1M***48 | Plate--Starting Instructions; Plate- Starting Instructions | 1 |
6h9200 Electric Starting Arrangement--24 Volt
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 4 |
| 1H***56 | Wrench--Glow Plug; Wrench- Glow Plug | 1 |
| 2H***79 | Wrench--Injection Valve Retainer Nut | 1 |
5h9496 Electric Starting Motor Group--24 Volt
| 5H***96 | Electric Starting Motor Group; Starting Motor Group | 1 |
6h9273 Ether Starting Aid Group
| 6H***73 | Ether Starting Aid Group | 1 |
6f6522 Exhaust Rain Trap Group--Diesel Engine
| 6F***22 | Exhaust Rain Trap Group | 1 |
4h2604 Exhaust Rain Trap Group--Starting Engine
| 4H***04 | Exhaust Rain Trap Group | 1 |
1m5895 Flood Lamp Assembly--6 Volt
| 1M***95 | Flood Lamp Assembly | 1 |
5k2001 Frame And Clamp Group--Side View--Type 3
| 5K***01 | Frame And Clamp Group | 1 |
5k2001 Frame And Clamp Group--Side View--Type 2
| 5K***01 | Frame And Clamp Group | 1 |
4k325 Frame And Clamp Group--Side View
| 4K***25 | Frame And Clamp Group | 1 |
2k5054 Frame And Clamp Group
| 2K***54 | Frame And Clamp Group | 1 |
5k2001 Frame And Clamp Group--Side View--Type 1
| 5K***01 | Frame And Clamp Group | 1 |
1k8923 Front Hydraulic Lines Group--Type 2
| 1K***23 | Front Hydraulic Lines Group | 1 |
1k8923 Front Hydraulic Lines Group--Type 1
| 1K***23 | Front Hydraulic Lines Group | 1 |
1m9528 Front Idler Group
| 1M***28 | Front Idler Group | 1 |
5m7814 Front Idler Group--Large Outside Diameter--Field Installation
| 5M***14 | Front Idler Group | 1 |
4h4803 Front Idler Group
| 4H***03 | Front Idler Group | 1 |
2m7389 Front Idler Group
| 2M***89 | Front Idler Group | 1 |
7h255 Fuel Priming Pump Group
| 7H***55 | Fuel Priming Pump Group | 1 |
8h6394 Gear Group--Field Changeover
| 8H***94 | Gear Group | 1 |
5h772 Generator--24 Volt, 18 Ampere
| 5H***72 | Generator | 1 |
8h1957 Generator--24 Volt, 18 Ampere
| 8H***57 | Generator Assembly | 1 |
5h3980 Generator Group--24 Volt, 18 Ampere--Type 4
| 5H***80 | Generator Group | 1 |
5h3980 Generator Group--24 Volt, 18 Ampere--Type 3
| 5H***80 | Generator Group | 1 |
5h3980 Generator Group--24 Volt, 18 Ampere--Type 1
| 5H***80 | Generator Group | 1 |
5h3980 Generator Group--24 Volt, 18 Ampere--Type 2
| 5H***80 | Generator Group | 1 |
5h3979 Glow Plug Group--24 Volt
| 5H***79 | Glow Plug Group | 1 |
4h6683 Grouser Group--18" Flat Center Shoe
| 4H***83 | Grouser Group | 1 |
4k354 Gusset Shoe Group
| 4K***54 | Gusset Shoe Group | 1 |
5h2067 Lamp--24 Volt
| 5H***67 | Head Lamp | 1 |
7f4625 Head Lamp--6 Volt
| 7F***25 | Head Lamp | 1 |
1m3377 Flood Lamp Assembly--6 Volt
| 1M***77 | Head Lamp Assembly | 1 |
7b4464 Front Pull Hook Group
| 7B***64 | Hook Group-Front Pull | 1 |
2k6177 Hydraulic Control Arrangement--50 G.P.M.--Single Valve
| 2K***53 | Supply Lines And Valve Group | 1 |
| 2K***67 | Hydraulic Lines Group | 1 |
| 2K***77 | Hydraulic Control Arrangement | 1 |
2k6180 Hydraulic Control Arrangements
| 2K***50 | Hydraulic Lines Group | 1 |
| 2K***53 | Supply Lines And Valve Group | 1 |
| 2K***54 | Lever Control Group | 1 |
2k6253 Hydraulic Control Arrangements
| 2K***50 | Hydraulic Lines Group | 1 |
| 2K***54 | Lever Control Group | 1 |
| 2K***67 | Hydraulic Lines Group | 1 |
2k9053 Hydraulic Front Lines Group--Type 1
| 2K***53 | Hydraulic Front Lines Group; Front Hydraulic Lines Group | 1 |
2k9053 Hydraulic Front Lines Group--Type 2
| 2K***53 | Hydraulic Front Lines Group; Front Hydraulic Lines Group | 1 |
2k8124 Hydraulic Lines Group
| 2K***24 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
4k1736 Hydraulic Lines Group--Front
| 4K***36 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
3k9321 Hydraulic Lines Group--Type 1
| 3K***21 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
1k8989 Hydraulic Lines Group--30" Extension--Second Type
| 1K***89 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
2k5550 Hydraulic Lines Group
| 2K***50 | Hydraulic Lines Group | 1 |
2k7298 Hydraulic Lines Group--Type 2
| 2K***98 | Hydraulic Lines Group | 1 |
2k6167 Hydraulic Lines Group--Rear
| 2K***67 | Hydraulic Lines Group | 1 |
1k8989 Hydraulic Lines Group
| 1K***89 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
5k2131 Hydraulic Lines Group--Front
| 5K***31 | Hydraulic Lines Group | 1 |
3k9321 Hydraulic Lines Group--Type 2
| 3K***21 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
2k6238 Hydraulic Lines Group--Front
| 2K***38 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
1k8989 Hydraulic Lines Group--30" Extension--Third Type
| 1K***89 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
2k7298 Hydraulic Lines Group--Type 1
| 2K***98 | Hydraulic Lines Group | 1 |
1m9543 Hydraulic Track Adjusting Group
| 1M***43 | Hydraulic Track Adjusting Group | 1 |
1m1882 Flood Lamp Assembly--24 Volt
| 1M***82 | Lamp Group | 1 |
9h6338 Dash Lamp Assembly--24 Volt
| 9H***38 | Lamp Group-Dash | 1 |
2k6517 Lever Control Group--Side
| 2K***17 | Lever Control Group | 1 |
2k5554 Lever Control Group--Front--Type 2
| 2K***54 | Lever Control Group | 1 |
2k5554 Lever Control Group--Front--Type 1
| 2K***54 | Lever Control Group | 1 |
2k6553 Lever Control Group--Side
| 2K***53 | Lever Control Group | 1 |
3k480 Lift Arm Extension Arrangement
| 1K***36 | Lift Arm Extension Group | 1 |
| 1K***89 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
| 3K***80 | Lift Arm Extension Arrangement | 1 |
1k8736 Lift Arm Extension Group
| 1K***36 | Lift Arm Extension Group | 1 |
2k3817 Lift Cylinder Arrangement
| 2K***51 | Lift Cylinder Group--R.H.,Lift Cylinder Group--L.H. | 1 |
| 2K***52 | Lift Cylinder Group--R.H.,Lift Cylinder Group--L.H. | 1 |
| 2K***17 | Lift Cylinder Arrangement | 1 |
2k2951 Lift Cylinder Group--R.H. 7 1/4" X 32"
| 2K***51 | Lift Cylinder Group--R.H.,Lift Cylinder Group--L.H. | 1 |
7h258 Lighting System Group--24 Volt--4 Lamp--Type 1
| 7H***58 | Lighting System Group | 1 |
7h258 Lighting System Group--24 Volt--4 Lamp--Type 2
| 7H***58 | Lighting System Group | 1 |
7h256 Lighting System Group--6 Volt--4 Lamp
| 7H***56 | Lighting System Group | 1 |
3k9768 Log Fork Cylinder Arrangement
| 3K***68 | Log Fork Cylinder Arrangement | 1 |
3k1786 Log Fork Group
| 3K***86 | Log Fork Group | 1 |
2k8415 Logging Fork Group--96" Wide
| 2K***15 | Logging Fork Group | 1 |
2k5939 Lumber Fork Group--Adjustable Width
| 2K***39 | Lumber Fork Group | 1 |
5h5565 Magnetic Switch
| 5H***65 | Magnetic Switch | 1 |
7h6700 Magnetic Switch
| 7H***00 | Magnetic Switch Assembly | 1 |
9h3580 Motor--24 Volt
5h455 Motor--24 Volt
| 5H***55 | Motor-Electric Starting | 1 |
7h3545 Muffler Group--Diesel Engine
| 7H***45 | Muffler Group | 1 |
3h8224 Primer
| 3H***24 | Primer | 1 |
3k9323 Pulpwood Fork Arrangement
| 1K***06 | Cylinder Group | 1 |
| 3K***21 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
| 3K***22 | Carriage And Clamp Group | 1 |
2k7301 Pulpwood Fork Arrangements
| 2K***76 | Cylinder Group | 1 |
| 2K***91 | Carriage And Clamp Group | 1 |
| 2K***98 | Hydraulic Lines Group | 1 |
1k8536 Pulpwood Fork Arrangements
| 1K***06 | Cylinder Group | 1 |
| 1K***65 | Carriage And Clamp Group | 1 |
| 1K***36 | Pulpwood Fork Arrangements | 1 |
4h7946 Regulator--24 Volt, 18 Ampere
| 4H***46 | Regulator | 1 |
6h9406 Regulator--24 Volt, 18 Ampere
| 6H***06 | Regulator | 1 |
9h6324 Regulator--24 Volt, 18 Ampere
| 9H***24 | Regulator Assembly | 1 |
2k8122 Side Dump Bucket Arrangement
| 2K***78 | Bucket And Support Group | 1 |
| 2K***22 | Side Dump Bucket Arrangement | 1 |
| 2K***23 | Cylinder Group | 1 |
9h1998 Spark Arrester Group--Diesel Engine
| 9H***98 | Spark Arrester Group | 1 |
2k4921 Spill Plate Extension Group
| 2K***21 | Spill Plate Extension Group | 1 |
6h1228 Starting And Glow Plug Switch
| 6H***28 | Starting And Glow Plug Switch | 1 |
2k5553 Supply Lines And Valve Group
| 2K***53 | Supply Lines And Valve Group | 1 |
2k6243 Supply Lines And Valve Group
| 2K***43 | Supply Lines And Valve Group | 1 |
7h4160 Regulator--24 Volt, 18 Ampere
| 7H***60 | Switch As | 1 |
7h7290 Switch Assembly
| 7H***90 | Switch As-Disconnect | 1 |
2k4811 Tooth Group
| 2K***11 | Tooth Group | 1 |
2k4745 Tooth Group
| 2K***45 | Tooth Group | 1 |
4k2023 Tooth Group
| 4K***23 | Tooth Group | 1 |
4k1735 Top Clamp Arrangement--Replaces 2k6249
| 2K***41 | Cylinder Group | 1 |
| 4K***25 | Frame And Clamp Group | 1 |
| 4K***35 | Top Clamp Arrangement | 1 |
5k2003 Top Clamp Arrangement
| 2K***41 | Cylinder Group | 1 |
| 5K***01 | Frame And Clamp Group | 1 |
| 5K***03 | Top Clamp Arrangement | 1 |
3k1756 Top Clamp Arrangements
| 2K***53 | Hydraulic Front Lines Group; Front Hydraulic Lines Group | 1 |
| 3K***81 | Cylinder Group--R.H.,Cylinder Group--L.H.; Cylinder Group-- R.H. | 1 |
| 3K***82 | Cylinder Group--R.H.,Cylinder Group--L.H.; Cylinder Group-- L.H. | 1 |
2k6249 Top Clamp Arrangements
| 2K***54 | Frame And Clamp Group | 1 |
| 2K***38 | Hydraulic Lines Group; Front Hydraulic Lines Group | 1 |
| 2K***49 | Top Clamp Arrangements | 1 |
2k9061 Top Clamp Arrangements
| 2K***57 | Cylinder Group | 2 |
| 2K***77 | Top Clamp Group | 1 |
| 2K***53 | Hydraulic Front Lines Group; Front Hydraulic Lines Group | 1 |
3k1701 Top Clamp Group
| 3K***01 | Top Clamp Group | 1 |
2k8477 Top Clamp Group
| 2K***77 | Top Clamp Group | 1 |
1m7923 Track Carrier Roller Group
| 1M***23 | Track Carrier Roller Group | 1 |
5m1589 Track Group--18" Flat Shoe--2 Groups Required
| 5M***89 | Track Group | 1 |
6h6035 Track Group--18" Triple Grouser Shoe--2 Groups Required--Type 2
| 6H***35 | Track Group | 1 |
9m4773 Track Group--16" Double Grouser Shoe--2 Groups Required
| 9M***73 | Track Group | 1 |
5h8872 Track Group--18" Flat Center Shoe--2 Groups Required
| 5H***72 | Track Group | 1 |
1m4576 Track Group--18" Triple Grouser Shoe--2 Groups Required
| 1M***76 | Track Group | 1 |
8m7376 Track Group--18" Flat Shoe--2 Groups Required
| 8M***76 | Track Group | 1 |
7m6824 Track Group--18" Flat Shoe--2 Groups Required
| 7M***24 | Track Group | 1 |
8m7375 Track Group--18" Triple Grouser Shoe
| 8M***75 | Track Group | 1 |
1s7281 Track Group--18" Double Grouser Shoe--2 Groups Required
| 1S***81 | Track Group | 1 |
2m9292 Track Group--18" Flat Shoe--2 Groups Required
| 2M***92 | Track Group | 1 |
1m1589 Track Group--18" Triple Grouser Shoe--2 Groups Required
| 1M***89 | Track Group | 1 |
5h8873 Track Group--18" Heavy Duty Flat Shoe--2 Groups Required
| 5H***73 | Track Group | 1 |
1m1593 Track Group--18" Flat Center Shoe--2 Groups Required
| 1M***93 | Track Group | 1 |
6h6035 Track Group--18" Triple Grouser Shoe--2 Groups Required--Type 1
| 6H***35 | Track Group | 1 |
1m1588 Track Group--18" Flat Shoe--2 Groups Required
| 1M***88 | Track Group | 1 |
8m7374 Track Group--18" Flat Shoe--2 Groups Required
| 8M***74 | Track Group | 1 |
7m6809 Track Group--18" Triple Grouser Shoe--2 Groups Required
| 7M***09 | Track Group | 1 |
7m6810 Track Group--18" Flat Shoe--2 Groups Required
| 7M***10 | Track Group | 1 |
6h6035 Track Group--18" Triple Grouser Shoe--2 Groups Required--Type 3
| 6H***35 | Track Group | 1 |
Track Groups--2 Groups Required
8m7303 Track Link Assembly--2 Assemblies Required
| 8M***03 | Track Link Assembly | 1 |
1s6878 Track Link Assembly--2 Assemblies Required--Replaces 8m7303
| 1S***78 | Track Link Assembly | 1 |
8h2462 Track Roller Frame Arrangement--Special Application
| 1F***91 | Roller Group-Track Carrier; Track Carrier Roller Group | 4 |
| 2F***85 | Track Roller Group; Track Roller Group- Single Flange | 6 |
| 2F***86 | Track Roller Group; Track Roller Group- Double Flange | 8 |
1m9483 Track Roller Frame Arrangement--Special Application
| 1A***99 | Pin- Drive | 3 |
| 1M***89 | Track Group | 2 |
| 1M***83 | Track Roller Frame Arrangement | 1 |
1m9388 Track Roller Frame Arrangement--Special Application
| 1A***99 | Pin- Drive | 1 |
| 1M***89 | Track Group | 2 |
| 1M***88 | Track Roller Frame Arrangement | 1 |
4h6111 Track Roller Frame Arrangement -- Special Application
| 1F***91 | Roller Group-Track Carrier; Track Carrier Roller Group | 4 |
| 2F***85 | Track Roller Group; Track Roller Group- Single Flange | 6 |
| 2F***86 | Track Roller Group; Track Roller Group- Double Flange | 8 |
1m413 Track Roller Frame Arrangement--Special Application--
| 1F***91 | Roller Group-Track Carrier; Track Carrier Roller Group | 4 |
| 1M***13 | Track Roller Frame Arrangement | 1 |
| 2F***36 | Fitting (1 5/16" Long) | 1 |
2m7390 Track Roller Frame Arrangement--Special Application
| 1A***99 | Pin- Drive | 3 |
| 1M***89 | Track Group | 2 |
| 1M***26 | Track Roller Group; Track Roller Group- Single Flange | 4 |
1m9324 Track Roller Frame Arrangement - Special Application
| 1A***99 | Pin- Drive | 3 |
| 1M***55 | Front Idler Group | 1 |
| 1M***03 | Roller Group-Track Carrier; Track Carrier Roller Group | 4 |
1m2000 Track Roller Frame Arrangement - Special Application
| 1A***99 | Pin- Drive | 3 |
| 1M***55 | Front Idler Group | 1 |
| 1M***00 | Track Roller Frame Arrangement | 1 |
1m9531 Track Roller Frame Group
| 1M***31 | Track Roller Frame Group | 1 |
4h4843 Track Roller Frame Guard Group
| 4H***43 | Track Roller Frame Guard Group | 1 |
1m3826 Track Roller Group--Single Flange--4 Groups Required
| 1M***26 | Track Roller Group; Track Roller Group- Single Flange | 1 |
Clutch, Transmission And Chassis
Brakes
Dash And Floor Plate
Final Drive--Part 1 Of 2
Final Drive--Part 2 Of 2
8m3992 Final Drive Seal Group--2 Groups Required
| 8M***92 | Final Drive Seal Group | 1 |
1h8500 Flywheel Clutch Group--Part 3 Of 3
| 1H***00 | Flywheel Clutch Group | 1 |
1h8500 Flywheel Clutch Group--Part 2 Of 3
| 1H***00 | Flywheel Clutch Group | 1 |
1h8500 Flywheel Clutch Group--Part 1 Of 3
| 1H***00 | Flywheel Clutch Group | 1 |
7m1934 Front Idler Group--Field Installation
| 7M***34 | Front Idler Group | 1 |
1m1955 Front Idler Group--Part 1 Of 2--Field Installation
| 1M***55 | Front Idler Group | 1 |
8h2464 Front Idler Group--Part 1 Of 2
| 8H***64 | Front Idler Group | 1 |
1m1955 Front Idler Group--Part 2 Of 2--Field Installation
| 1M***55 | Front Idler Group | 1 |
3h1820 Front Idler Group
| 3H***20 | Front Idler Group | 1 |
8h2464 Front Idler Group--Part 1 Of 2--Field Installation
| 8H***64 | Front Idler Group | 1 |
1m1955 Front Idler Group--Part 2 Of 2
| 1M***55 | Front Idler Group | 1 |
8h2464 Front Idler Group--Part 2 Of 2--Field Installation
| 8H***64 | Front Idler Group | 1 |
8h2464 Front Idler Group--Part 2 Of 2
| 8H***64 | Front Idler Group | 1 |
1m1955 Front Idler Group--Part 1 Of 2
| 1M***55 | Front Idler Group | 1 |
Fuel System
Fuel Tank And Seat Support
Gear Shift And Flywheel Clutch Control--Part 2 Of 2
Gear Shift And Flywheel Clutch Control--Part 1 Of 2
Hood And Guard
4h4806 Main Frame Support Group
| 4H***06 | Main Frame Support Group | 1 |
3h1871 Main Frame Support Group
| 3H***71 | Main Frame Support Group | 1 |
2h2714 Oil Pump Group
| 2H***14 | Oil Pump Group | 1 |
1m2003 Track Carrier Roller Group--4 Groups Required
| 1M***03 | Roller Group-Track Carrier; Track Carrier Roller Group | 1 |
1m2003 Track Carrier Roller Group--4 Groups Required--Field Installation
| 1M***03 | Roller Group-Track Carrier; Track Carrier Roller Group | 1 |
1f3791 Track Carrier Roller Group--4 Groups Required
| 1F***91 | Roller Group-Track Carrier; Track Carrier Roller Group | 1 |
Seat Cushions
Steering Clutch
3h1870 Steering Clutch Control Group
| 3H***70 | Steering Clutch Control Group | 1 |
7b8429 Steering Clutch Group
| 7B***29 | Steering Clutch Group | 1 |
Steering Clutch Hydraulic Control Mechanism--Part 2 Of 2
Steering Clutch Hydraulic Control Mechanism--Part 1 Of 2
9b572 Track Carrier Roller Group--4 Groups Required
| 9B***72 | Track Carrier Roller Group | 1 |
5h9037 Track Group--18" Triple Grouser Shoe--2 Groups Required
| 5H***37 | Track Group | 1 |
1m4575 Track Group--18" Flat Shoe--2 Groups Required
| 1M***75 | Track Group | 1 |
2m9295 Track Group--18" Triple Grouser Shoe--2 Groups Required
| 2M***95 | Track Group | 1 |
4h4393 Track Group--18" Flat Shoe--2 Groups Required
| 4H***93 | Track Group | 1 |
3h1678 Track Roller Frame Group--Field Installation
| 3H***78 | Track Roller Frame | 1 |
Track Roller Frame (3h1678 N/S)
| 3H***78 | Track Roller Frame | 1 |
4h4808 Track Roller Frame Group
| 4H***08 | Track Roller Frame Group | 1 |
3h1866 Track Roller Frame Guard Group
| 3H***66 | Track Roller Frame Guard Group | 1 |
8h2463 Track Roller Frame Guard Group
| 8H***63 | Track Roller Frame Guard Group | 1 |
4f3521 Track Roller Group--Single Flange--4 Groups Required
| 4F***22 | Track Roller Group; Track Roller Group- Double Flange | 1 |
8h780 Track Roller Group--Single Flange--6 Groups Required--Field Installation--Type 1
| 8H***81 | Track Roller Group | 1 |
2f3085 Track Roller Group--Single Flange--6 Groups Required
| 2F***85 | Track Roller Group; Track Roller Group- Single Flange | 1 |
8h780 Track Roller Group--Single Flange--6 Groups Required
| 8H***81 | Track Roller Group | 1 |
8h780 Track Roller Group--Single Flange--6 Groups Required--Field Installation--Type 2
| 8H***81 | Track Roller Group | 1 |
Transmission Case And Covers--Part 2 Of 2
Transmission Case And Covers--Part 1 Of 2
1s1831 Transmission Conversion Group
| 1S***31 | Transmission Conversion Group | 1 |
3h2616 Transmission Group--Part 2 Of 2
| 3H***16 | Transmission Group | 1 |
7h7577 Transmission Group--Part 2 Of 2
| 7H***77 | Transmission Group | 1 |
7h7577 Transmission Group--Part 1 Of 2
| 7H***77 | Transmission Group | 1 |
3h2616 Transmission Group--Part 1 Of 2
| 3H***16 | Transmission Group | 1 |
1h8499 Universal Joint
| 1H***99 | Universal Joint As | 1 |
Diesel Engine
Accessory Shaft And Idler Gear
Air Cleaner
4f3567 Basic Governor Group--Part 1 Of 2
| 4F***67 | Basic Governor Group | 1 |
4f3567 Basic Governor Group--Part 2 Of 2
| 4F***67 | Basic Governor Group | 1 |
Breather And Oil Filler
Camshaft
5h2634 Complete Governor Group
| 5H***34 | Complete Governor Group | 1 |
Compression Release Control
Connecting Rod And Piston--6 Required
Connecting Rod And Piston--6 Groups Required
Crankshaft
Crankshaft Bearing Replacement Groups
Cylinder Block And Covers--Front View-Part 2 Of 2
Cylinder Block And Covers--Side View - Part 1 Of 2
5h7505 Cylinder Block Assembly
| 5H***05 | Cylinder Block Assembly | 1 |
Cylinder Head And Valve Mechanism--Side View - Part 1 Of 2
Cylinder Head And Valve Mechanism--End View - Part 2 Of 2
Engine Support
1l655 Fan And Water Pump Group
| 1L***55 | Fan And Water Pump Group | 1 |
4f6734 Fuel Filter Group
| 4F***34 | Fuel Filter Group | 1 |
Fuel Injection Valves And Lines
Fuel Pump And Governor Control
Fuel Pump Housing
5f6607 Fuel Transfer Pump Group
| 5F***07 | Fuel Transfer Pump Group | 1 |
5h8033 Governor Control Group--Positive Locking
| 5H***33 | Governor Control Group | 1 |
4f8125 Hour Meter Group
| 4F***25 | Hour Meter Group | 1 |
Manifolds
9f6428 Oil Filter Assembly
| 9F***28 | Oil Filter Assembly | 1 |
Oil Gauge, Fuel Gauge And Heat Indicator
Oil Lines
2h7105 Oil Pump Assembly
| 2H***05 | Oil Pump Assembly | 1 |
4f6916 Oil Pump Drive Group
| 4F***16 | Oil Pump Drive Group | 1 |
6h6617 Oil Pump Drive Group
| 6H***17 | Oil Pump Drive Group | 1 |
Radiator And Oil Cooler
6h3821 Radiator And Oil Cooler Group
| 6H***21 | Radiator And Oil Cooler Group | 1 |
8h5218 Service Meter Group--Field Installation--Type 2
| 8H***18 | Service Meter Group | 1 |
8h5218 Service Meter Group--Field Installation--Type 3
| 8H***18 | Service Meter Group | 1 |
8h5218 Service Meter Group
| 8H***18 | Service Meter Group | 1 |
Water Lines
4f6789 Water Lines Group
| 4F***89 | Water Lines Group | 1 |
Hydraulic Control
1j4750 Control Valve Group
| 1J***50 | Control Valve Group | 1 |
Hydraulic Lines
Hydraulic Mounting
3k6609 Hydraulic Oil Filter Group
| 3K***09 | Hydraulic Oil Filter Group | 1 |
Hydraulic Pump
Hydraulic Pump And Lines--Top View--Part 2 Of 2
Hydraulic Pump And Lines--Side View--Part 1 Of 2
Hydraulic Pump And Mounting
4m7229 Hydraulic Pump Assembly
| 4M***29 | Hydraulic Pump Assembly | 1 |
7h7733 Hydraulic Pump Group
| 7H***33 | Hydraulic Pump Group | 1 |
6h9554 Hydraulic Pump Group
| 6H***54 | Hydraulic Pump Group | 1 |
Hydraulic Pump Lines
Hydraulic Valve And Tank--Front View--Part 1 Of 2
Hydraulic Valve And Tank--Front View - Part 1 Of 2
Hydraulic Valve And Tank--Side View--Part 2 Of 2
Hydraulic Valve And Tank--Side View - Part 2 Of 2
Hydraulic Valve Hand Control
2k3891 Lift Cylinder Group--R.H.--Type 1
| 2K***91 | Lift Cylinder Group R H,Lift Cylinder Group L H | 1 |
2k3891 Lift Cylinder Group--R.H.--Type 2
| 2K***92 | Lift Cylinder Group R H,Lift Cylinder Group L H | 1 |
6h3862 Hydraulic Oil Filter Group
| 6H***62 | Oil Filter Group | 1 |
5h8004 Relief Valve Assembly
| 5H***04 | Relief Valve Assembly | 1 |
6h8267 Relief Valve Assembly
| 6H***67 | Relief Valve Assembly | 1 |
2k3893 Tilt Cylinder Group--R.H.
| 2K***93 | Tilt Cylinder Group R H,Tilt Cylinder Group L H | 1 |
2h4300 Universal Joint
| 2H***00 | Universal Joint | 1 |
4h5830 Universal Joint
| 4H***30 | Universal Joint | 1 |
5m798 Universal Joint Assembly--Field Installation
| 5M***98 | Universal Joint Assembly | 1 |
5m797 Universal Joint Assembly
| 5M***97 | Universal Joint Assembly | 1 |
No. 977a Bulldozer
8f6362 Blade Group
| 8F***62 | Blade Group | 1 |
8f6373 Brace Group
| 8F***73 | Brace Group; Brace Group | 1 |
2k4997 Bulldozer Arrangement--Angling Blade
| 2K***97 | Bulldozer Arrangement | 1 |
2j6684 Bulldozer Arrangement--Angling Blade
| 2J***84 | Bulldozer Arrangement | 1 |
2k5356 Bulldozer Group--Straight Blade--104" Wide
| 2K***56 | Bulldozer Group | 1 |
8f8912 C--Frame Group
| 8F***12 | C--Frame Group | 1 |
2j6657 C--Frame Group
| 2J***57 | C--Frame Group | 1 |
2k7476 Counterweight Group--Rear Mounted--2400 Pounds
| 2K***76 | Counterweight Group | 1 |
3k6940 Counterweight Group--2400 Pounds
| 3K***40 | Counterweight Group | 1 |
4h9108 Drawbar Group--Swinging Type--Type 2
| 4H***08 | Drawbar Group | 1 |
4h9108 Drawbar Group--Swinging Type - Type 1
| 4H***08 | Drawbar Group | 1 |
8f9866 Grease Gun
| 8F***66 | Grease Gun As | 1 |
1f221 Hose Assembly
| 1F***21 | Hose Assembly | 1 |
7h3933 Hose Assembly
| 7H***33 | Hose Assembly | 1 |
Name Plates And Transfers
| 1H***38 | Transfer Safety First | 1 |
| 1H***17 | Transfer; --Lubricating Oil Filter Instructions | 1 |
| 3H***42 | Plate--Serial Number (Track Loader); On Bevel Gear & Steering Clutch Case--Upper Rear Of L.H. Side | 2 |
6h9833 Tool Group
| 6H***33 | Tool Group | 1 |
3h4472 Tool Group
| 3H***72 | Tool Group | 1 |
1m9849 Tool Group
| 1M***49 | Tool Group | 1 |
9h2687 Tool Group
| 9H***87 | Tool Group | 1 |
2k5116 Trunnion Group
| 2K***16 | Trunnion Group | 1 |
2j6700 Trunnion Group
| 2J***00 | Trunnion Group | 1 |
4b1856 Volume Compressor
| 4B***56 | Volume Compressor | 1 |
7h1680 Volume Compressor
| 7H***80 | Volume Compressor | 1 |
Starting Engine
4f6802 Air Cleaner, Breather And Carburetor Group
| 4F***02 | Air Cleaner Breather And Carburetor Group | 1 |
6h3822 Battery Group--6 Volt
| 6H***22 | Battery Group | 1 |
5f3525 Carburetor
| 5F***25 | Carburetor | 1 |
6h5298 Carburetor Control Group
| 6H***98 | Carburetor Control Group | 1 |
7b9920 Clutch And Starter Pinion Group
| 7B***20 | Clutch And Starter Pinion Group | 1 |
8h7323 Clutch And Starter Pinion Group
| 8H***23 | Clutch And Starter Pinion Group | 1 |
3h1877 Clutch Housing Group
| 3H***77 | Clutch Housing Group | 1 |
Crankshaft, Camshaft, Connecting Rod And Piston
Cylinder Block, Cylinder Head And Valve Mechanism--End View--Part 2 Of 2
Cylinder Block, Cylinder Head And Valve Mechanism--Side View--Part 1 Of 2
Cylinder Block, Cylinder Head And Valve Mechanism--End View - Part 2 Of 2
6h3825 Electric Starting Motor Group--6 Volt
| 6H***25 | Electric Starting Motor Group | 1 |
Fuel System
8h1963 Generator--6 Volt, 40 Ampere
| 8H***63 | Generator | 1 |
9f5094 Generator--6 Volt, 40 Ampere
| 9F***94 | Generator | 1 |
2m6664 Generator--6 Volt, 40 Ampere
| 2M***64 | Generator Assembly | 1 |
5h4105 Generator Group--6 Volt, 40 Ampere
| 5H***05 | Generator Group | 1 |
5h4105 Generator--6 Volt, 40 Ampere
| 5H***05 | Generator Group | 1 |
4b4054 Governor Group
| 4B***54 | Governor Group | 1 |
3h4037 Ignition System Group
| 3H***37 | Ignition System Group | 1 |
7f9937 Magneto
| 7F***37 | Magneto | 1 |
9h4479 Magneto
| 9H***79 | Magneto | 1 |
4s6470 Magneto Assembly--Field Installation
| 4S***70 | Magneto Assembly | 1 |
7b2421 Motor--6 Volt
6h9206 Regulator--6 Volt, 40 Ampere
| 6H***06 | Regulator | 1 |
7h4150 Regulator--6 Volt, 40 Ampere
| 7H***50 | Regulator | 1 |
7f4702 Regulator--6 Volt, 40 Ampere
| 7F***02 | Regulator | 1 |
9h6316 Regulator--6 Volt, 40 Ampere
| 9H***16 | Regulator Assembly | 1 |
Starter Pinion Control
6h5303 Starter Pinion Control Group
| 6H***03 | Starter Pinion Control Group | 1 |
4b3929 Water Pump Group
| 4B***29 | Water Pump Group | 1 |
Traxcavator
2k3896 Bucket Assembly--2 1/4 Cu. Yd.--96" Wide
| 2K***96 | Bucket Assembly | 1 |
Bucket Control
Bucket Positioner
Frame
4h4015 Hitch Group
| 4H***15 | Hitch Group | 1 |
Kickout
977A serial number reference
The PIN plate is a durable metal identification plate, usually riveted to the machine frame. To read the prefix, identify the first three alphanumeric characters preceding the dash or leading digits of the serial number.
| Prefix | Identifies | Notes |
|---|---|---|
| 20A | 977 (Early Production) | Covers serial numbers 20A1 and up. Features a D318 naturally aspirated 6-cylinder diesel engine rated near 75 kW (100 hp) at 1,800 rpm. Includes a gasoline pony motor for starting. Transmission is a direct-drive 5-speed gearbox with a 2-speed transfer case using hand-lever steering clutches and foot brakes. Operating weight approximately 15,900 kg (34,980 lb). Fuel tank capacity 227 L (50 US gal). Configuration is standard loader only; no dozer blade or width options documented for this range. |
| 53A | 977 (Later Production) | Covers serial numbers 53A1 and up. Engine progression includes D318, then D333 diesel, and later a turbocharged D333T rated near 112 kW (150 hp). Steering system changed from hand-lever clutches/foot brakes to pedal steering at unit 53A4797 (circa 1964). Oil-cooled brakes and steering clutches added at 53A01907 (circa 1961). |
Frequently asked questions
What engine is used in the Caterpillar 977A?
Early production (20A-prefix) units utilize the D318, a 6-cylinder, naturally aspirated, liquid-cooled diesel engine with an 8.6 L (524 cu in) displacement. Later 53A-prefix production transitioned to the D333 diesel engine.
What is the operating weight of this machine?
The 20A-prefix configuration has an operating weight of approximately 15,900 kg (34,980 lb). Weight figures for other configurations in the 977 family vary by source and serial range.
What models replaced the 977A?
The 977A was part of a lineage of lettered generations that included the 977D, 977H, 977K, and 977L.
What 977A owners discuss
What are the primary engine differences between early and later production 977 series machines?
Early production (20A-prefix) units utilize a D318 6-cylinder, naturally aspirated diesel engine rated at approximately 100 hp (7/5 kW) at 1,800 rpm. Later 53A-prefix production transitioned from the D318 to the D333 diesel, eventually including a turbocharged D333T variant rated near 150 hp (112 kW). Note that higher-output turbo engines like the Cat 3306 are associated with later lettered generations such as the 977H, 977K, and 977L, not the base 977 series specifications.
How does the steering and braking configuration change across the 977 production run?
Early 977 models feature hand-lever operated dry steering clutches and mechanical brakes. A mid-production change occurred at unit 53A4797 in 1964, where Caterpillar introduced pedal steering and oil-cooled steering clutches and brakes. The 53A01907 serial range specifically marks the addition of oil-cooled components.
What are the common maintenance concerns regarding the powertrain and hydraulic systems?
For direct-drive models, steering clutch and brake band assemblies are prone to lining wear due to torque routing through these components; they require periodic relining or rebuilding. In the final drives, avoid using straight gear oil as the additive package can damage seals; use SAE 50 powertrain oil meeting Cat TO-4/TDTO specifications instead. For hydraulic systems, check for leaks in lines and cylinders, particularly on older units that have sat idle.
What should be monitored during engine oil sampling for these vintage diesel engines?
Since the 977 is a fully mechanical machine without an ECM or fault codes, oil sampling is the primary diagnostic tool. Monitor samples for metal content to identify gear or bearing wear in the transmission and final drives, and check specifically for coolant intrusion, which is a known wear point on these wet-liner blocks.
What are the typical undercarriage and attachment maintenance requirements?
Regular inspections should include checking track tension and adjusting if loose. Track rollers, idlers, and sprocket wear must be evaluated every 500 hours. For attachments, inspect loader lift and tilt linkage pivot points for lubrication needs and check for rod resurfacing or resealing requirements on cylinders after long-term service.
What is the most critical item to check when purchasing a used Caterpillar 977?
Verify the exact serial number prefix (e.g., 20A vs 53A) before purchase, as this determines if the machine has hand-lever or pedal steering and which engine is installed. Additionally, inspect for signs of 'welded repairs' on bucket pins or linkages, as some owners may weld components shut rather than replacing worn pins. Always verify final drive oil condition for signs of contamination.
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific 977A part?
Search live OEM part data, check fitment, and cross-reference alternatives with Heavy Parts AI.