Transmission teardown and rebuild anchor this 602-page Clark GPX 30 service manual PDF, which widens to Perkins gas/LPG and Phaser/1000 diesel engine sections, IMPCO fuel, brakes, steering and uprights for five GPX forklift truck variants from the 30 up to the 50. Wiring diagrams and the color code let you trace a dead circuit wire by wire, and the hydraulic schematic maps the lift, tilt and valve circuit so your pressure check reads against something real. Troubleshooting charts cover cooling, steering, pump and upright faults; the Perkins engine sections fill a large share of the book. Pull the axle end and overhaul the caliper once piston linings wear to 0.125 inch (3 mm), and clean the IMPCO vaporizer-regulator every 1000 hours or 6 months. A made-up torque on engine mounting bolts can let a mount work loose under load. Buy it once and the bookmarked, text-searchable PDF stays yours for as long as you run this truck.
What's Inside This Clark GPX/DPX 30/35/40/40S/50/55 Manual
| System | Pages | Key Topics |
|---|---|---|
| Introduction | 6-23 | Safety, Planned Maintenance |
| Engine Removal and Replacement | 24-34 | Engine Removal, Engine Replacement, Counterweight Removal, Radiator Removal |
| Perkins Workshop Manual - Gas/LPG Engines | 35-50 | Engine Views, General Information, Engine Number, Specifications |
| Perkins Workshop Manual - Periodical Attentions and Fault Finding | 51-56 | Maintenance Schedules, Post Delivery Checkover, Starting Procedures, Fault Finding Chart |
| Perkins Workshop Manual - Cylinder Head and Pistons | 57-69 | Cylinder Head Removal, Valve Maintenance, Piston and Connecting Rod Assembly, Cylinder Block and Liners |
| Perkins Workshop Manual - Crankshaft, Timing, and Lubrication | 70-94 | Crankshaft Bearings, Balancer Unit, Timing Case and Drive, Lubrication System, Oil Pump |
| Perkins Workshop Manual - Cooling and Fuel Systems | 95-113 | Water Pump, Thermostat, Carburetor, Fuel Lift Pump, Governor and Distributor Drive |
| Perkins Workshop Manual - Electrical Equipment | 114-133 | Distributor, Alternator, Dynamo, Starter Motor, Consumable Products |
| Perkins Phaser/1000 Series Diesel Engines | 134-286 | Engine Identification, Cylinder Head Assembly, Piston and Connecting Rods, Crankshaft Assembly, Timing Case and Drive, Lubrication System, Fuel System, Cooling System |
| Cooling System | 287-296 | Troubleshooting, Cooling System Testing and Maintenance, Fan Belt Replacement, Radiator Removal |
| Fuel System | 297-324 | Fuel Pump Pressure Test, IMPCO Fuel System, Carburetor Overhaul, Velocity Governor Overhaul, Removal of IMPCO Vaporizing System |
| Transmission | 325-376 | Transmission Checks, Draining and Refill, Transmission Removal, Transmission Overhaul |
| Electrical System | 377-394 | Wiring Color Code, Wiring Diagrams, Electrical Checks |
| Drive Axle | 395-417 | Axle End Lubrication, Axle End Removal, Axle Ends Overhaul, Differential Overhaul |
| Wheels and Tires | 418-429 | Lifting, Jacking, And Blocking, Wheels and Tires Mounting |
| Braking/Inching System | 430-449 | System Description/Troubleshooting, Brake and Inching System Bleeding, Brake and Inching Pedals Adjustment, Master Cylinder Overhaul, Power Booster Overhaul, Brake Caliper Overhaul |
| Steering Column and Gear | 450-474 | Troubleshooting, Steering Column and Gear Removal, Char-Lynn Steering Control Unit |
| Steer Axle | 475-492 | Steer Axle Removal, Steer Axle Overhaul, Steering System Adjustment, Steer Cylinder Removal, Steer Axle Wheel Bearings, Steer Cylinder Overhaul |
| Hydraulic Sump, Filters, and Pump | 493-501 | Hydraulic Sump and Filters, Pump Troubleshooting and Overhaul |
| Hydraulic Valve/Lift Circuit | 502-516 | Hydraulic System Pressure Check, Hydraulic Valve Overhaul, Hydraulic Valves, Hydraulic Schematic |
| Tilt Cylinders | 517-525 | Tilt Cylinder Removal, Tilt Cylinder Overhaul, Tilt Lock Valve |
| Uprights | 526-569 | Troubleshooting and Visual Inspection, Operational Checks, Carriage Check and Adjustment, Upright Check and Adjustment, Cylinder Repair, Lift Chain Maintenance |
| Counterweights | 570-573 | Counterweight Removal and Reinstallation |
| Specifications | 574-602 | Namplates/Decals, PM Inspection and Drivers Daily Inspection Forms, Recommended Lubricants & Lubricant Specifications, Lubrication Intervals |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Engine Mounting Bolts | 164-184 N-m (121-136 lbf-ft.) | p. 588 |
| Transmission to Engine Bolts | 33-37 N-m (24-27 lbf-ft.) | p. 588 |
| Vaporizer-regulator cleaning interval | 1000 hours or 6 months of operation | p. 309 |
| Model J vaporizer-regulator rating | 12 gallons/hr. | p. 308 |
| Piston lining wear limit | 0.125 inch (3mm) | p. 447 |
| Disk lining minimum thickness | 0.1 inch (2.5 mm) | p. 447 |
| Hydraulic Fluid Flush Amount | 2 quarts | p. 495 |
| Hydraulic Sump Drain Interval | Every 2000 hours or once a year | p. 495 |
| Chain wear replacement limit | 3% or more | p. 533 |
| Fork heel wear limit | 10% smaller than the arm | p. 535 |
| Maximum wear limit for chain span | 3% | p. 563 |
| Engine Oil Pressure (at max engine speed) | 30-60 lbf/in² (2.1-4.2 kgf/cm²) | p. 49 |
Clark GPX/DPX 30/35/40/40S/50/55 Common Problems This Manual Covers
Clark GPX LPG engine with IMPCO fuel system hard starting, erratic idle, or hunting at governed RPM
Check the vaporizer-regulator settings against the specs on page 584: primary at 10 kPa (1.45 psi) and secondary at 38 mm water column. Look for frost or ice on the valves, then remove and clean the vaporizer-regulator, which page 309 calls for every 1000 hours or 6 months of operation.
Manual Section: Fuel System p. 297Upright will not lift the load to maximum height, with sluggish lift speeds
Check the hydraulic sump level first; on Gas/LPG trucks the sump holds 17 L (17.9 qt) per page 582. Then work through the upright troubleshooting and operational checks starting on page 526, inspect the carriage and upright adjustment, and look for oil leaks at the lift cylinders before condemning the pump.
Manual Section: Uprights p. 526Vane type hydraulic pump showing low flow, foam in the oil, or failing to build pressure
Check the fluid level in the hydraulic sump and inspect the suction line filter (100 µm wire cloth, page 587) for restriction. If the oil is foamed or overheated, drain the sump, flush the tank with 2 quarts of clean hydraulic fluid as page 495 describes, replace the filters, and refill.
Manual Section: Hydraulic Sump, Filters, and Pump p. 493Hydraulic valve load drift, spool failing to return, or no relief valve action
Test hydraulic system pressure following the procedure in the Hydraulic Valve/Lift Circuit section on page 502 to confirm relief valve action. If the spool sticks or the load keeps drifting, remove the valve for overhaul and trace the circuit against the hydraulic schematic on page 516 before reassembly.
Manual Section: Hydraulic Valve/Lift Circuit p. 502Steering control unit hard or slow steering, wander, drift, or temporary hang-up
Check the steering column and gear troubleshooting chart on page 450 before pulling anything. If the unit locks up, oscillates, or hangs up, remove the Char-Lynn steering control unit for inspection, then verify steering system adjustment at the steer axle following page 475 so you are not chasing a setup problem.
Manual Section: Steering Column and Gear p. 450Radiator cooling system overheating with temperature light on, or engine running too cold
Test the cooling system following the troubleshooting procedures on page 288, checking for water pump noise and oil in the coolant. Inspect the fan belt and replace it if worn, check the thermostat covered on page 95, and remove the radiator for service if testing points there.
Manual Section: Cooling System p. 288Frequently Asked Questions
What are the hydraulic oil and filter replacement specs for the Clark GPX/DPX 30/35/40/40S/50/55 forklift?
The hydraulic sump fluid should be drained and replaced every 2000 operating hours. Replace the hydraulic oil filter elements at every oil change. Additionally, remove, clean, and reinstall the hydraulic and steer system suction line screens at the first planned maintenance interval and every 500 hours thereafter. p. 20
What is the torque spec for the cylinder head nuts and setscrews on a Clark GPX/DPX 30/35/40/40S/50/55 forklift?
The cylinder head nuts and setscrews should be tightened to a torque of 96 lbf ft (13.2 kgf m or 130 Nm). p. 49
What is the correct valve tip clearance for the G4.236 engine in the Clark GPX/DPX 30/35/40/40S/50/55?
The running clearance for the inlet valve is 0.012 inches (0.30 mm) and 0.015 inches (0.38 mm) for the exhaust valve, measured when cold. p. 49
What is the recommended oil pressure for the G4.236 engine in the Clark GPX/DPX 30/35/40/40S/50/55?
The oil pressure should be between 30 and 60 lbf/in² (2.1 to 4.2 kgf/cm²) at maximum engine speed and normal operating temperature. p. 49
How often should the engine crankcase oil be changed?
It is recommended to drain and replace the engine crankcase oil every 50 to 250 operating hours, depending on application and operating conditions. p. 20
How quickly can I access this Clark GPX 30 manual after buying?
Straight to your device: 602 pages of searchable Service Manual, downloadable the moment payment goes through.
Are there any print restrictions on this Clark GPX 30 manual?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
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