Terex 2566C, 2766C, 3066C Articulated Dumptruck Service & Repair Manual (P/N SM 991 Rev 2)

• Official Terex Equipment Limited publication SM 991 Rev 2 (May 1998) for the 2566C, 2766C, and 3066C Articulated Dumptrucks. Supplied as a 529-page, two-file PDF set: the 492-page service manual and a 37-page landscape drawing file.
• Matches the machine to its powertrain configuration before repair work begins: Cummins 6CTA8.3-C engines with ZF 6WG 200 Powershift transmissions for the 2566C/2766C, plus the Cummins MTA11-C300 with ZF 6WG 250 or 6WG 260 Automatic transmission coverage for the 3066C.
• Documents chassis, articulation, axle, and driveline repair, including frame straightening and welding, pivot bearing and bushing service, driveshaft inspection, limited-slip differential setup, planetary wheel-end work, suspension struts, air springs, and leveling-valve service.
• Covers steering, braking, and pneumatic workshop procedures such as steering-valve and pump overhaul, steering-cylinder resealing, accumulator testing and charging, brake-head rebuilding and bleeding, pressure-converter repair, control-valve testing, and air-dryer service.
• Details body-hoist hydraulic diagnosis and repair through factory schematics, test points, fault charts, hydraulic-tank and filter service, body-cylinder disassembly and resealing, pump inspection, control-valve overhaul, and the 6WG 260 pilot-operated joystick system.
• Includes model-specific electrical and diagnostic reference, with ZF measuring-point charts, oil-circulation diagrams, 24-volt wiring drawings, service-tool references, torque specifications, pressure-test data, capacities, wear limits, and adjustment information.

Chassis, Axles, and Driveline

The chassis section explains frame inspection, hydraulic straightening, weld repair, reinforcement, and the electrical precautions required before welding. Articulation and oscillation coverage includes pivot driveshaft bearings, articulation bearings and retainers, oscillation bushings, thrust adjustment, and a diagnosis chart for noise, looseness, and vibration at the joint.

Axle repair is treated at assembly level. The manual shows differential and limited-slip unit disassembly, bearing and gear inspection, pinion and carrier setup, backlash and tooth-contact checks, axle-group removal and installation, brake-component service, and planetary wheel-end construction. Front suspension coverage adds the air spring and leveling valve; the rear sections address the suspension struts and center axle differential.

Driveline procedures include removal, disassembly, inspection, reassembly, installation, lubrication, and fault isolation. One important assembly trap is clearly documented: the slip-joint arrows and wing-bearing match marks establish shaft phasing and balance. Losing those relationships during repair can introduce the vibration the technician is trying to eliminate.

Powertrain and Body-Hoist Systems

Engine coverage is machine-side service for the Cummins 6CTA8.3-C and MTA11-C300 installations. It includes engine removal and installation, mountings, air cleaner, cooling and lubrication checks, filters, belts, viscous-fan service, and the 2566C exhaust-brake arrangement. Full internal Cummins engine overhaul is outside this Terex publication and is referred to the engine manufacturer’s service information.

The ZF chapters explain transmission operation, lockup and retarder circuits, differential-lock and PTO arrangements, shift solenoids, switches, sensors, pressure measuring points, oil flow, mounting, removal and installation, and oil/filter maintenance. The 3066C receives separate 6WG 250 and 6WG 260 coverage, including dedicated electrical drawings and the 6WG 260 body-control joystick and pilot-supply valve. Internal ZF transmission overhaul is likewise referred to the transmission manufacturer’s manual.

Body-hoist sections cover the hydraulic tank, filtration, pump, cylinders, control valve, linkage, and model-specific circuits. The cylinder chapter includes removal, disassembly, seal inspection and replacement, reassembly, and installation. The pump section warns that its drive and driven gears are a matched set and that incorrect gear or cover indexing can cause binding or internal damage.

Electrical Drawings, Diagnostics, and Shop Data

The separate drawing file contains six transmission test and oil-flow sheets plus 31 model- and transmission-specific electrical sheets for the 2566C/2766C, 3066C, and 3066C with 6WG 260. Useful references include ZF gear-pattern and measuring-point charts, lockup-clutch/retarder oil-circulation diagrams, the steering-system schematic, body-hoist schematics, air and hydraulic brake schematics, and 24-volt wiring drawings with transmission-module interfaces.

The service-tool section identifies items such as the 15269784 Multi-Gauge, 15018226 diagnostic coupling, and 15004085 hose assembly, along with axle pullers, seal drivers, nitrogen-charging equipment, R-134a service equipment, and fabrication drawings for steering, cylinder, pump, and body-lifting tools.

Component-specific torque tables, approved fluid and capacity data, pressure-test specifications, electrical checks, clearances, wear limits, and adjustment data appear with the related repair sections. Safety material addresses supported raised bodies, stored hydraulic and pneumatic pressure, nitrogen accumulators, refrigerant handling, rotating driveline parts, electrical isolation, and the hazard of fire-damaged fluoro-elastomer seals.

This set is intended for chassis, axle, steering, brake, body-hoist, electrical, and machine-side powertrain repair on the three listed models, with the model-specific drawings needed to select the correct circuit and test point before disassembly.