1960–1963 David Brown 850, 880, 950 & 990 Tractor Repair Manual Set (P/N DBT. 445 & DBT 499)

Use the Service Information supplement with the Repair Manual. It supplies model-specific changes and service data alongside the dismantling, overhaul, and reassembly procedures in the main publication.

Industrial and crawler applications are identified in the diesel-engine section. The 990 Industrial also has a dedicated twin-plate clutch section.

PDF Search, Circuit Detail and Page Count

Search and diagram viewing: PDF text search is unavailable, and there are no embedded bookmarks. Small labels in the starter and regulator circuit diagrams are easier to read when zoomed in.

One printable 162-page PDF in English contains both publications. The total includes ten title or section-cover pages and six blank pages.

Engine, Clutch and Implematic Hydraulic Work

The overview below highlights selected topics. The PDF includes additional repair procedures, technical data and illustrations.

• Engine overhaul: Step-by-step procedures for engine removal, cylinder-head service, piston and connecting-rod removal, cylinder-sleeve replacement, and timing-gear work.

• Engine support systems: Injector testing, D.P.A. injection-pump removal and timing, lubrication-system service, water-pump repair, and thermostat testing.

• Clutch repair: Single-plate and Livedrive double-clutch removal, overhaul, release-mechanism adjustment, fault diagnosis, and the 990 Industrial twin-plate arrangement.

• Transmission and brakes: Gearbox and differential disassembly, crown-wheel adjustment, reduction-unit service, axle-case oil-seal replacement, brake adjustment, and relining.

• Implematic hydraulics: Symptom-based fault finding, leakage and pressure tests, pump overhaul, control-valve service, top-link cable adjustment, and automatic hold-mechanism settings.

• Steering and front axle: Axle and hub service, wheel alignment, recirculating-ball steering-box overhaul, and U281/U282 power-assisted steering installation and repair.

• Electrical testing: Battery checks, starter bench tests, dynamo repair, regulator and cut-out adjustment, with component circuit diagrams and test connections.

Written for distributor and dealer workshops, these instructions assume the knowledge of a competent engineering fitter.

Engine Overhaul and Workshop Tooling

The engine section covers the AD4/40T and AD4/40U powerplants, with related AD4/36 applications. Inspection data addresses pistons, connecting rods, crankshaft bearings, and camshaft journals.

Cylinder-sleeve work identifies remover 901729 and protrusion-checking tool 902169. The head-tightening sequence, cylinder-head and valve section view, and piston-ring cross sections support the accompanying inspection and assembly instructions.

The manual warns that carbon can resist exhaust-valve removal even when the valve was not sticking in service; forceful extraction can bend the stem or valve head.

Fuel Injection, Lubrication and Cooling

Injector coverage includes pressure, back-leakage, dry-seat, and atomization tests, followed by nozzle cleaning and reassembly. Injector-pocket notes distinguish washer requirements for later heads from the earlier loose-copper-sleeve arrangement.

The D.P.A. section covers pump removal, refitting, and timing alignment, supported by timing-mark illustrations and a section through the injection-pump drive gear. Fuel-delivery setting requires suitable bench equipment; the text directs suspect pumps to a C.A.V. agent for checking and resetting.

Lubrication coverage includes oil-pump dismantling, bush replacement, and relief-valve testing. Cooling procedures address water-pump seals and bearings, thermostat operation, and coolant circulation.

Clutch, Gearbox and Final-Drive Differences

Livedrive procedures distinguish the transmission clutch from the PTO clutch. The 990 Industrial twin-plate arrangement instead transmits both plates through a single driveshaft. Clutch access also differs between six-speed and twelve-speed tractors.

Gearbox instructions cover shaft clearances, differential bearings, crown-wheel tooth-contact assessment, and differential-lock assembly. A dimensioned gearbox support-stand drawing helps with bench preparation.

The supplement identifies non-interchangeable 990 main-drive gears and explains that Narrow tractors do not have a differential lock. Reduction-unit data separates the bearing arrangements used on the 990/950 from those on the 880/850.

Hydraulic Fault Isolation and Lift-Control Service

The Implematic fault chart leads into tests for valve linkage, ram-cylinder relief, depth-control operation, internal leakage, pump pressure, and piston sealing. These tests help distinguish an adjustment fault from a component problem before dismantling.

Early and later ram-cylinder arrangements receive separate treatment, including the linkage locking bolt and later automatic catch. Further procedures cover the top-link compression unit, flexible cable, automatic hold mechanism, and U279 three-way valve.

A separate hydraulic section addresses the earlier 950 T/U system and Dowty pump. The pump instructions warn that hammering the drive shaft can damage its comparatively soft rotor bushes.

Steering, Electrical Equipment and Accessories

Front-axle instructions distinguish forged and fabricated beams, high-clearance axles, and Narrow-model hubs. Power-assisted steering coverage includes the Eaton pump, control valves, hydraulic ram, fault finding, and overhaul.

Electrical procedures address the Lucas M45G starter, C39P-2 dynamo, and RB108 regulator. Starter and control-unit circuit diagrams are included; the complete tractor wiring diagram is referenced in the separate tractor Instruction Book.

Accessory material includes exhaust-brake fitting and component identification for U362, U442, and U371. The drawbar-frame material is a continuation page rather than a complete fitting guide.

Always review and strictly adhere to all listed factory safety precautions and load limits before initiating any heavy mechanical work or lifting operations on these machines.

Cold Valve Clearance and Ring-Gap Examples

The Service Information lists cold intake-valve clearance at 0.015 in. (0.38 mm) across the four Implematic models. Cold exhaust clearance is also 0.015 in. on the 850, 880, and 950, while the 990 uses 0.012 in. (0.30 mm).

The piston dimensional data lists a new piston-ring gap of 0.010–0.015 in., alongside ring side-clearance and piston-fit specifications.