Swing motor wear limits on a Quantum-series machine live in exactly one place, and this Link-Belt 3900Q shop manual PDF is it: 624 pages of factory service data for your 3900Q excavator, from undercarriage rollers to hydraulic cylinders. Hydraulic schematics trace the pilot and main circuits through pump, control valve, and travel motor, while wiring diagrams map the electrical system and maintenance standards tables give you wear limits for rollers, idlers, and reduction gears. Teardown procedures for the travel and swing motor assemblies fill a large share of the book, each closing with reassembly torques and troubleshooting charts. Check brake release signal pressure at 426.5 to 710.9 psi, and inspect hoses and lines every 50 hours. A final drive half apart is no time to hunt a bearing spec. Bookmarked and text-searchable, this PDF also prints clean, so the pages can ride the bench and take the grease.
What's Inside This Manual
| System | Pages | Key Topics |
|---|
| Explanation | 3-14 | Contents, Safety, Introduction, Symbols Used, Precautions, Standard Torque Specifications, Numerical Value Conversion Table |
| General | 15-44 | Safety, Precautions |
| Specifications | 45-70 | Major Equipment Specifications, Filters, Fluids and Lubricants |
| Performance | 71-78 | Main Body Weight, New Machine Performance Check List, Suspension Performance |
| Main Body Disassembly and Servicing Procedures | 79-138 | Lower Mechanism, Upper Mechanism, Attachment, Maintenance Standards |
| Major Components Disassembly and Servicing Procedures | 139-190 | Tightening Torque for Major Parts, Take-Up Roller, Recoil Spring, Upper Roller, Lower Roller, Rotating Joint |
| Hydraulic Pump Instruction and Maintenance | 191-214 | Hydraulic Pump Handling, Regulator Instruction, Pump Disassembly, Pump Reassembly, Maintenance Standards |
| Travel Mechanism Motor Assembly | 215-366 | Motor Assembly, Reduction Gear, Troubleshooting, Maintenance Standards, Special Jigs |
| Swing Mechanism Motor Assembly | 367-478 | Swing Motor Assembly, Reduction Gear, Relief Valve Maintenance, Troubleshooting, Structure Diagrams |
| Control Valve Operations and Maintenance | 479-528 | Control Valve Principles, Disassembly, Reassembly, Relief Valve Maintenance, Troubleshooting |
| Hydraulic Cylinder Specifications and Maintenance | 529-624 | Cylinder Structure, Disassembly Procedures, Reassembly Procedures, Maintenance Standards, Troubleshooting |
Quick Reference Specifications
| Specification | Value | Page |
|---|
| Oil seal inclination allowance | 0.008 inch per 3.937 inch (0.2 mm at 100 mm) | p. 31 |
| Fuel tank mounting bolts torque | 184.4-213.4 ft lbs (252-289.3 N-m) | p. 53 |
| Fuel tank sensor cover bolts torque | 9.4 ft lbs (12.75 N-m) | p. 54 |
| Maintenance Interval for Hoses and Lines | Every 50 hours | p. 69 |
| Brake release port signal pressure | 426.5 - 710.9 psi (30 - 50 kgf/cm²) | p. 409 |
| Relief valve adjustment shim pressure change | 71.09 psi (5 kgf/cm²) | p. 412 |
| Rated Pressure | 568.7 psi (3.92 MPa) | p. 619 |
| Rated Voltage | DC 24 Volt | p. 589 |
| Travel Motor Suction Capacity | 7.9/5.0 in³/rev | p. 49 |
| Travel Motor Working Pressure | 4975 psi | p. 49 |
| Engine Displacement | 504.7 in³ | p. 53 |
| Engine Rated Horsepower | 138 kW | p. 53 |
