The International Harvester 574, 674 and 784 tractors are among the best-known medium-sized IH utility tractors. They were used widely for general farm work, loader duties, PTO work and transport, and many remain in service or restoration today.
This guide covers the 574, 674 and 784 family in general. Engines, transmissions, hydraulic systems, PTO arrangements, brakes, steering and electrical equipment vary by model, year and market. Use the correct workshop manual for the exact tractor and serial range.
1. The IH 574 / 674 / 784 Family
These tractors sit in the well-known IH utility range and share a broad design philosophy while differing in power and detail.
Typical uses included:
- General cultivation
- Hay and baling
- Loader work
- Livestock duties
- Road transport
- PTO-powered machinery
2. International Harvester 574
The 574 was a popular medium-sized tractor with a reputation for solid mechanical construction.
Depending on market and year, it may be found with different engine and transmission specifications.
3. International Harvester 674
The 674 offered more power while retaining the same broad utility-tractor character.
Many components appear similar to the 574, but exact interchangeability should not be assumed.
4. International Harvester 784
The 784 belongs to the later development of the same utility concept and includes further changes in:
- Engine output
- Transmission details
- Hydraulics
- Operator environment
- Electrical controls
5. Identify Before Ordering Parts
Record:
- Model number
- Serial number
- Engine identification
- Transmission type
- Hydraulic-control layout
- PTO arrangement
Bonnet panels, wheels, cabs, engines and rear-end components may have been changed during decades of work.
6. Diesel Engine
Diesel versions are especially common.
When assessing the engine, check:
- Cold starting
- Oil pressure
- Blow-by
- Exhaust smoke
- Coolant condition
- Fuel leaks
7. Hard Starting
Before blaming the injection pump, check:
- Battery condition
- Starter speed
- Compression
- Fuel supply
- Fuel filters
- Air in the fuel system
- Cold-starting aid
- Injection timing
8. Fuel Injection System
Mechanical diesel injection systems depend on clean fuel and correct timing.
Common faults include:
- Blocked filters
- Air leaks
- Injector wear
- Return-line leaks
- Pump leakage
9. White Smoke on Start-Up
Possible causes include:
- Low compression
- Slow cranking
- Incorrect injection timing
- Poor injector spray
- Cold combustion chamber
10. Black Smoke Under Load
Check:
- Air filter
- Fuel setting
- Injector condition
- Engine load
- Turbo/air system where fitted
11. Engine Oil Pressure
Low hot oil pressure may be caused by:
- Bearing wear
- Oil-pump wear
- Relief-valve leakage
- Incorrect oil
Confirm with a proper gauge before dismantling.
12. Cooling System
Inspect:
- Radiator
- Water pump
- Fan belt
- Thermostat
- Hoses
- Coolant condition
13. Transmission
IH utility tractors were available with differing transmission arrangements.
Before repair, identify whether the tractor uses:
- Standard manual gearing
- Hi-Lo or range arrangements
- Additional ratio-changing systems where fitted
14. Gearbox Noise
Possible causes include:
- Low oil
- Water contamination
- Bearing wear
- Gear wear
- Incorrect end float
15. Difficult Gear Selection
Check:
- Clutch drag
- Linkage wear
- Selector adjustment
- Internal transmission wear
16. Clutch
Common complaints include:
- Slipping
- Dragging
- Release-bearing noise
- Sticking after storage
17. PTO System
PTO arrangements differ by tractor specification.
Check:
- Engagement mechanism
- Clutch relationship
- Shaft condition
- Oil leakage
- Brake/stop behaviour where fitted
18. PTO Will Not Engage
Possible causes include:
- Linkage fault
- Clutch adjustment
- Hydraulic control issue
- Internal PTO wear
19. Hydraulic System
Hydraulics typically power:
- Three-point linkage
- Remote valves
- Loader functions where fitted
- Steering on some arrangements
20. Linkage Will Not Raise
Check:
- Oil level
- Filter condition
- Pump supply
- Control linkage
- Relief valve
- Internal leakage
21. Linkage Weak When Hot
Possible causes include:
- Pump wear
- Internal leakage
- Lift-cylinder leakage
- Incorrect or contaminated oil
22. Linkage Drifts Down
Possible causes include:
- Lift-cylinder leakage
- Control-valve leakage
- Check-valve leakage
23. Remote Hydraulics
Check:
- Quick couplers
- Spool valves
- Flow restriction
- Oil condition
- Added loader plumbing
24. Steering
Depending on model and specification, steering may be:
- Power assisted
- Hydrostatic
- Other hydraulic arrangements
Identify the actual system fitted before diagnosis.
25. Weak Steering
Possible causes include:
- Low hydraulic oil
- Pump wear
- Priority valve fault
- Steering cylinder leakage
- Steering valve wear
26. Front Axle Wear
Loader tractors often wear at:
- Centre pivot
- Kingpins
- Wheel bearings
- Steering joints
27. Brakes
Brake design varies by model and production period.
Check:
- Pedal travel
- Brake balance
- Linkage movement
- Oil contamination
- Internal wear
28. Final Drives and Rear Axle
Listen for:
- Bearing rumble
- Gear whine
- Knocking under load
Inspect for leaks at:
- Half shafts
- Final drives
- Brake housings
29. Electrical System
Common age-related faults include:
- Poor earths
- Corroded terminals
- Charging faults
- Modified wiring
- Failed switches
30. Cab and Controls
Later tractors may have more complex cab wiring and controls than earlier open-platform models.
Check:
- Lighting
- Instruments
- Heater/fan
- Switchgear
- Safety interlocks where fitted
31. Long-Storage Problems
- Stuck clutch
- Water in transmission/hydraulic oil
- Seized brakes
- Blocked fuel system
- Perished hoses
- Corroded wiring
- Tyre deterioration
32. Water in Transmission Oil
Milky oil may result from:
- Outdoor storage
- Damaged boots
- Breathers
- Condensation
Water contamination can affect both transmission and hydraulic performance.
33. Before First Start After Storage
- Confirm engine turns freely.
- Check oil and coolant.
- Clean fuel supply.
- Inspect air intake.
- Check transmission/hydraulic oil.
- Inspect clutch and brakes.
- Check wiring and battery cables.
- Confirm throttle and stop controls operate.
34. Buying an IH 574 / 674 / 784
Check:
- Correct identity
- Cold starting
- Oil pressure
- Blow-by
- Transmission noise
- Clutch operation
- PTO operation
- Hydraulic lift under load
- Steering play
- Brake performance
35. Restoration Order
- Identify tractor and major components.
- Make engine and cooling system reliable.
- Repair brakes and steering.
- Repair clutch, transmission and PTO.
- Repair hydraulics.
- Tidy electrics and cab equipment.
- Finish with paint and cosmetics.
36. Workshop Checklist
| System | Check |
|---|---|
| Identification | 574, 674 or 784 and serial range confirmed. |
| Engine | Cold start, smoke, oil pressure and blow-by. |
| Transmission | All ranges and gears operate correctly. |
| Clutch/PTO | No slip/drag; PTO engages correctly. |
| Hydraulics | Linkage and remotes strong and responsive. |
| Steering | No excessive play or hydraulic weakness. |
| Brakes | Balanced and effective. |
| Electrics | Charging, starting and controls sound. |
| Oil condition | No water or heavy contamination. |
Related Agrimanual Manuals
- Search Agrimanual International 574 manuals
- Search Agrimanual International 674 manuals
- Search Agrimanual International 784 manuals
- Request an International Harvester manual if the exact version is not listed
Frequently Asked Questions
Are the 574, 674 and 784 mechanically identical?
No. They share a broad IH utility-tractor lineage, but engines, transmissions, hydraulics, brakes and equipment differ between models and years.
Why does the hydraulic lift become weak when hot?
Oil thinning can reveal pump wear or internal leakage. Test the system before replacing the pump.
Why is my IH difficult to identify?
Many tractors have had engines, cabs, bonnets or rear-end components changed. Use serial numbers and actual component details.
Why does the PTO not stop properly?
Depending on the system, check clutch adjustment, linkage, PTO brake/stop mechanism and internal wear.
Can water in the transmission oil affect hydraulics?
Yes. Where systems share oil, contamination can affect both lubrication and hydraulic performance.
The IH 574, 674 and 784 family remains popular because these tractors combine useful power with straightforward mechanical systems. Correct identification and clean hydraulic/transmission oil are especially important when restoring one today.