Case 780CK / 780 Construction King Backhoe Loader: Specs, Parts & Common Issues
The launch machine of the largest Case backhoe loader nameplate. Produced 1971 – 1981, the 780CK (commonly referenced as simply "780") brought the turbocharged Case A336 BDT engine — 336 cu in, 4-cylinder, 120 HP gross — to the Construction King family. Class-leading breakout and dig depth for the 1970s, on a 24V electrical system and outboard-planetary final drives.
The Case 780CK — referenced simply as "780" in much of the factory literature — is the launch machine of the largest Case backhoe loader nameplate. It came to market in 1971 and ran through 1981, sitting above the 680E/G in Case's lineup as the company's biggest industrial backhoe loader of the era. The 780 nameplate inherits the "CK" Construction King designation from the earlier 680CK and 580CK launch machines, though "CK" was largely dropped from common reference once the platform was established.
The defining 780CK detail is the engine: a turbocharged version of the Case 336 cu in four-cylinder diesel — designated A336 BDT — making 111 HP net / 120 HP gross. That's a substantial step up from the contemporary 680E's naturally aspirated 80 HP version of the same 336 block, and it gave the 780CK class-leading breakout force and lift capacity for a backhoe loader in the 1970s. The platform ran for over a decade before the 780B took over in 1981 with refinements but the same core architecture.
At-a-glance specifications
Case 780 / 780CK — factory specifications
- Production years
- 1971 – 1981
- Successor
- Case 780B (1981 – 1985)
- Engine
- Case A336 BDT (turbocharged)
- Cylinders
- 4, turbocharged, liquid-cooled, direct-injection diesel
- Displacement
- 336 cu in (5.5 L)
- Bore × stroke
- 4.625 in × 5.00 in (117 × 127 mm)
- Power (net)
- 111 HP (82.8 kW) @ 2,200 rpm
- Power (gross)
- 120 HP (89.5 kW)
- Peak torque
- 329 lb-ft (446 Nm) @ 1,500 rpm
- Compression ratio
- 16.5:1
- Engine oil capacity
- 11 qts (10.4 L)
- Coolant capacity
- 26 qts (24.6 L)
- Transmission
- Power shuttle, 4F / 4R
- Drive
- 2WD
- Final drives
- Outboard planetary
- Electrical
- 24V system, dual battery
- Brakes
- Hydraulically actuated dry-disc
- Hydraulic system
- Open-center, gear pump
- Hydraulic pressure
- ~2,000 – 2,500 psi
- Operating weight
- ~16,500 – 18,000 lb (varies with configuration)
- Length
- ~23 ft
- Width
- ~7.5 ft
- Height
- ~11 ft
- Cab
- Optional enclosed cab
The A336 BDT engine — what "BDT" means and why it matters
The Case A336 BDT is the turbocharged version of the Case 336 cu in four-cylinder diesel that powered the 680E (naturally aspirated), 680G (naturally aspirated with higher output), and 680H (naturally aspirated). The "B" in BDT refers to the engine series; the "D" stands for diesel; the "T" stands for turbocharged. The 780CK gets a 4.625-inch bore and the wastegated turbo to feed denser intake air for the increased output.
- 120 HP gross / 111 HP net — substantially above the naturally aspirated 336 engines that ran 80–88 HP in the 680 series.
- 329 lb-ft peak torque at 1,500 rpm — strong working torque for digging.
- 24V starting — the same 24V electrical architecture that runs on the 680H, 850 dozer, and W14 wheel loader. Allows the larger starter motor needed to spin a turbocharged engine in cold weather.
Power shuttle and outboard-planetary final drives
The 780CK uses Case's power shuttle transmission with single-stage torque converter — four forward and four reverse speeds, hydraulically actuated direction changes without a foot clutch, and outboard planetary final drives at the rear axle. The outboard-planetary layout puts the final reduction gearset at the wheel hub rather than at the differential output — a stronger arrangement for heavy industrial applications.
Service items on the power shuttle are predictable: clutch packs wear, the shuttle valve gets sticky, and the torque converter charge pump weakens with age. The Case 780 / 780CK service manual is the authoritative reference for shuttle service procedures.
Hydraulic system
Open-center hydraulics driven by a gear pump. Working pressure is in the 2,000–2,500 psi range, sufficient for the larger backhoe and loader cylinders the 780CK carries. The 780CK's hydraulics are not as advanced as the later L-generation load-sensing systems, but they are robust and serviceable with standard Case hydraulic components.
Parts we carry
The 780CK is over 40 years old. Direct parts availability for the original CK platform is limited compared to later 780B / 780C / 780D machines, but several items cross-fit through the 680-line ecosystem and the broader Case industrial parts network. Items confirmed at Broken Tractor with 780-series fitment include:
| Part # | Part | Notes |
|---|---|---|
| F44629 | Upper rear cab glass | Long-fitment upper rear glass: 580D, 680K, and "780 series" (covers 780CK, 780B, 780C, 780D cab-equipped machines). One part number for the entire 780 line. |
| F44630 | Lower rear cab glass | Matching lower rear glass: 580D / Super D / Super E / 680H / 780 series. Replace alongside the F44629 when the cab is being re-glazed. |
| D40037 | Greaseable pin | Greaseable pin with Case industrial cross-fit: 680E, 780, 850 dozer, W11, W11B wheel loaders. Used at common pivot points across the Case industrial line. |
| A176539 (R46156) | 24V starter motor | The 24V starter that runs on the 680H, 780B, 850C, and W14 family. The 780CK's 24V system uses a closely related starter — confirm exact fitment by serial number before ordering. |
For 780CK service literature, the Case 780 / 780CK loader backhoe manual (available through Case parts channels and aftermarket reproduction sources) is the most authoritative reference for diagnosis and repair. Many engine-specific parts cross to the broader Case 336-class engine ecosystem; turbocharger and head gasket components may have separate availability through Case industrial channels.
Common issues and what to expect
A336 BDT engine wear
The Case A336 BDT is durable but well past expected service life on any original-engine 780CK still in operation. Common issues: head gasket failure (40-plus-year-old gaskets are typically failed or near-failed), turbocharger bearing wear, valve seat recession, and injection pump wear. Plan on a full engine rebuild as a baseline restoration step on any unrestored 780CK.
Power shuttle clutch wear
Same wear pattern as the contemporaneous 680E/G. Clutch packs wear with age and use, the shuttle control valve gets sticky, and the torque converter charge pump weakens. Service involves dropping the rear casting.
24V electrical system
The 24V starting and charging system on a 40-plus-year-old machine has corroded battery cables, marginal connections, and likely a starter or alternator that has been replaced multiple times. The R46156 / A176539 24V starter is the verified replacement for closely related machines; confirm fitment for the 780CK specifically before ordering.
Cab glass and seal aging
The F44629 and F44630 cab glass items are common replacement parts on a 780CK that has been outdoor-stored. 40-plus-year-old rubber seals are typically hard and brittle.
Hydraulic cylinder seal failure
Every cylinder on a 780CK has seals that are 40-plus years old. Plan on rebuilding every cylinder as part of any restoration. Bores are typically still good; reseal kits are usually sufficient.
Working on a Case 780CK?
The 780CK is a parts-availability challenge — the platform is old, the population is small, and many original-fitment items have to be sourced through cross-references or aftermarket reproductions. Our specialists can help track down the right components by serial number, engine ID, and physical comparison.
Mon – Fri, 7:00 AM – 5:00 PM CT
Contact Broken TractorWhere it sits in the 780 family
The 780CK is the founding machine of the 780 line. After 1981 the 780B took over with refinements (1981–1985), followed by the 780C in the late 1980s (sharing the Cummins B-series 6T-590 engine with the 680L and 780D), and finally the 780D closing out the line in the 1990s. Across the line, the 780 family was Case's largest standard backhoe loader nameplate — above the 680 line, which itself sat above the 580 family. Today the Case 590 Super N is the largest production backhoe loader in Case's lineup, occupying a slot smaller than the original 780 series.
