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A natural extension of the Cat® product line, the Cat CT681 Vocational Truck delivers all the power, performance and productivity you expect from Caterpillar. This Class 8 set-forward axle model—ideal for hauling heavy loads—features a spacious and ergonomic cab, industrial styling, vocational-specific engine and transmission options, and bumper-to-bumper support across North America.


Engine Model Cat® CT13 Engine Cat® CT13 Engine Less
Horsepower @ 1700 rpm 365 - 430 hp (268 - 316 kW) 365 - 430 hp (268 - 316 kW) Less
Bore 4.96 in 12.6 cm Less
Engine Type Diesel, 4-Cycle Diesel, 4-Cycle Less
Configuration Inline 6-Cylinder Inline 6-Cylinder Less
Stroke 6.54 in 16.6 cm Less
Compression Ratio 17:1 17:1 Less
Displacement 758.0 in3 12.4 L Less
Aspiration Dual Series Turbochargers, Intercooler and Aftercooler Dual Series Turbochargers, Intercooler and Aftercooler Less
Combustion System Direct Injection Direct Injection Less
Lubrication System Capacity 42.0 qt 40.0 l Less
Coolant Drain Interval 600,000 miles (965,606 km) 600,000 miles (965,606 km) Less
Total Engine Weight (Dry) 2400.0 lb 1089.0 kg Less
Width 37.0 in 94.0 cm Less
Length 59.0 in 150.0 cm Less
Height 49.0 in 125.0 cm Less
Valves 4 Valves Per Cylinder, Overhead Cam Actuated 4 Valves Per Cylinder, Overhead Cam Actuated Less
Peak Torque @ 1000 rpm 1550 lb-ft (2102 N-m) 1550 lb-ft (2102 N-m) Less


Maximum Gross Input Power 550.0 hp 410.0 kW Less
Maximum Gross Input Torque 1700.0 lb ft 2400.0 N·m Less
Transmission Model Cat CX31® Automatic Transmission Cat CX31® Automatic Transmission Less
Speeds 6 forward/1 reverse 6 forward/1 reverse Less
Torque Converter: Cast aluminum design with lock up clutch Cast aluminum design with lock up clutch Less
Clutches: Electro-hydraulic fully modulated, oil cooled, multidisc Electro-hydraulic fully modulated, oil cooled, multidisc Less
Maximum Input Speed: 2500 rpm 2500 rpm Less
Length 35.3 in 896.0 mm Less
Overall Length with Retarder Option 39.4 in 1000.0 mm Less
Overall Weight (approx.) 906.0 lb 411.0 kg Less
Overall Weight with Retarder Option 1088.0 lb 494.0 kg Less
Power Take-Off Two side locations and a Cat exclusive high output rear PTO Two side locations and a Cat exclusive high output rear PTO Less
Rear PTO Capacity (rotation opposite of engine, at 1.25 engine speed) 800.0 ft-lb 1356.0 N·m Less
Side PTO Capacity (rotation same as engine, ratio determined by PTO adaptor) 700.0 ft-lb 950.0 N·m Less

Heavy-Hauling Capacity

The CT681’s set-forward axle, rugged design and industrial styling make it ideal for hauling heavy loads or working in extreme conditions. Aluminum alloy cab construction reduces overall weight for maximum payloads.

Attachment-Ready Design

Our integral Front Frame Extension (FFE) option makes it easy to mount attachments like snow plows, hose reels, winches and hydraulic pumps. Mixer installation is simple thanks to vertical tie-in plates mounted behind the cab.

Shift-Long Productivity

Comfortable drivers are safe, productive drivers. The CT681’s wide, spacious cab is filled with ergonomic details to reduce fatigue and thoughtful features to enhance driver comfort, all shift long.

Safer Driving

Our ergonomically designed dashboard and center stack layout give drivers complete command and control. All controls, levers, switches and gauges are positioned to maximize safety and minimize fatigue, so drivers can stay focused on the job at hand.

Smooth, Quiet Ride

Our tuned cab air suspension system, premium grade sound insulation kit, and durable routing and clipping wire system dramatically reduce vibration and cab noise.

Vocational-Specific Power

Under the hood, the CT681 is powered by a Cat CT Series Vocational Truck Engine with ratings specific to vocational truck applications and a horsepower/torque combination to tackle the toughest jobs.

Automatic Shifting

Performance-matched with your engine to deliver rugged durability, smooth shifting and optimum power, the Cat CX31 Automatic Transmission will help you maximize your CT681’s uptime, fuel economy and productivity. (Other transmission options are available.)

Unmatched Support

Your CT681 comes with the best on-the-ground support team in the business. Your Cat dealer not only offers bumper-to-bumper service, but also can help you order the exact truck you need with expertise on custom options ranging from transmissions to suspensions and axles.

CT681Standard Equipment

  • Set-forward axle, 114-inch bumper to back of cab (BBC)
  • 12.25-inch rail size: 120,000 psi yield strength
  • Above-rail radiator

  • Meritor & Dana options
  • 6x4 truck configuration

Front Suspension
  • Parabolic taper leaf for a smoother ride
  • Shock absorbers standard
  • Optional two-stage, multi-leaf, shackle-type with shocks

Rear Suspension
  • Hendrickson offerings: HMX, RT/RTE, RS, R & PriMaax
  • Chalmers standard & high articulation
  • Capacities from 40,000-85,000 lbs.

Fuel Tank
  • 80-, 100- & 120-gallon capacities
  • Single left or dual under cab/back of cab options
  • Aluminum alloy construction

CT681Optional Equipment

  • Integral Front Frame Extension (FFE)

  • Cat CX31 Automatic Transmission
  • A variety of manual transmissions and the Ultrashift® Plus Vocational Transmission built by Eaton

On-Board Technology
  • Vehicle Infotainment System
  • Bendix Tire Pressure Monitoring System