Description

O&K RH 3, RH 9 1974 Technical Manual – Factory OEM Specs

If you’re working on an O&K RH 3, RH 9 1974 Technical Manual you already know the pain of hunting down factory specs for these old German excavators. Aftermarket documentation leaves out half the details – especially the DIN symbols for hydraulics, pneumatics, and electrical circuits. I’ve seen guys torque a swing motor housing to wrist-snap values because they trusted a reprint from a third-party. This is the real deal: OEM print from O&K, 187 pages, original 1974 release. No guesswork.

Page count alone doesn’t tell you much. What matters is that every section – from Basic Principles through Replacement of Wear Parts – was written for the tech holding the wrench. The foreword states: “scrupulous cleanliness and order at the place of work are pre-requisites for all repair work.” They assume you’re qualified, so they skip the kindergarten stuff. You get the actual DIN symbols, fluid specs (imperial equivalents where applicable), and stepwise disassembly procedures. Need to know charge pressure for the hydraulic pump? Page 73 – but only if you read the functional description chapter first.

Basic Principles: DIN Symbols and Hydraulics

Chapter 1 starts with DIN symbols for hydraulics, pneumatics, electrical engineering, and welding techniques. If you’ve ever stared at a circuit diagram that looks like spaghetti, this section gives you the key. They explain a simple hydraulic circuit diagram using actual German industry standards (DIN). Then they walk through the formulas – no shortcuts, just the math you need to calculate flow and pressure. The oil and grease specifications are listed with original part numbers. Don’t substitute with cheaper stuff unless you want seal failures.

Functional Descriptions: What the Manual Actually Covers

The main group index splits the book into four parts: Basic Principles, Functional Descriptions, Inspection Instructions, and Replacement of Parts. The Functional Descriptions chapter (around 40 pages) breaks down each major system – track drive, swing mechanism, boom hydraulics, and the electrical control circuit. O&K used a mix of 12V and 24V systems depending on the year; this manual covers both. You’ll find schematic diagrams with component callouts. Cross-reference the item numbers from the illustrations to the parts list at the start of each sub-group.

Inspection Instructions: How to Check Before You Tear Down

Jump to Chapter 3 if you suspect component wear. The inspection instructions are procedure-by-procedure: checking hydraulic cylinder drift, measuring pump flow, testing relief valve cracking pressure. They give acceptable wear limits – no generic “replace if worn” garbage. For example, they specify max radial play for the swing gear pinion. You’ll need a dial indicator and a press. Clean everything with the right solvent (they warn against steam jets on rubber or electrical parts).

Replacement of Wear Parts and Assemblies

Chapter 4 is the meat for anyone doing a major overhaul. It covers replacing seals, bearings, hydraulic lines, and complete assemblies like the final drive or the control valve bank. Each procedure includes disassembly sequence, required tools (you’ll need a puller set and a torque wrench that can do ft-lb and in-lb), and torque values in both metric and imperial. The manual reminds you to replace paper seals and O-rings on every repair – and they mean every. I’ve had guys skip that step and come back with a leak.

Electrical System: DIN Symbols and Wiring

One of the biggest pain points on these old excavators is the electrical system. The manual dedicates an entire sub-group (1.2) to DIN symbols for electrical engineering. They show the actual symbols used in the wiring diagrams – not that generic “this represents a resistor” nonsense. If you’re chasing a short in the instrument panel or a dead start solenoid, you need those symbols. The functional description chapter includes the full schematic for the power distribution and safety interlocks.

Source Authenticity: Why OEM Beats Aftermarket

I’ve been burned by aftermarket manuals that rephrase the OEM text but change the torque values. This is a direct factory print from O&K Orenstein & Koppel AG, 1974. The copyright page says “Vervielfältigung nicht gestattet” – reproduction not permitted. That means no reprints, no third-party copies. Every page number matches the original binder layout. If you want to do it right, you need the OEM source.

Frequently Asked Questions

Does this manual cover both the RH 3 and RH 9 models?

Yes. The title says RH 3 – RH 9, and the content applies to both. The differences (engine options, track frame variations) are handled in the sub-group notes.

What torque specifications are included? Can I use it for a full rebuild?

The manual includes torque values for critical fasteners: cylinder gland nuts, bearing caps, swing gear bolts, and hydraulic line connections. They’re listed in the replacement chapters and in the final functional description section. However, this is a technical handbook – it gives the theory and procedures. For a full rebuild you’ll also want the separate parts manual for exploded views and part numbers. That said, the torque data is directly from O&K engineering. Follow the sequence specified in the procedure, and use a calibrated torque wrench. If you’re doing a complete engine or transmission rebuild on the truck that carries this excavator, you’ll need a separate Manual Transmission service guide. For the hydraulic system on the O&K, this manual is all you need.

Related Manuals

• O&K 4000 Technical Manual
• O&K 1500 Technical Manual
• O & K Trojan L2000 Parts Catalog – OEM Factory 131-Page Manual

If your shop deals with O&K excavators from the 1970s, you know the value of factory documentation. This 187-page technical manual gives you the DIN symbols, inspection criteria, and replacement procedures you need to keep those RH 3 and RH 9 machines running. Don’t trust aftermarket reprints. Access the Factory Manual from AutoRepairManuals and put the real specs on your bench. For additional information on manual transmissions used in some models, refer to Manual Transmission resources elsewhere – but for the O&K hydraulic and electrical systems, this is your only source.