John Deere 6404 Specifications
| Engine Model: John Deere 6404 |
| Engine Type: 4-stroke in-line 6-cylinder liquid-cooled diesel |
| Total Displacement: 404 cu.in (6.6 L) |
| Rated Engine Power: 95-130 Hp (70.5-96 kW) at 2200-2500 rpm |
| Fuel System Type: Direct Injection |
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The John Deere 6404 is a 404 cubic inch (6.6
liter), naturally aspirated or turbocharged, inline-6 diesel engine
produced by John Deere primarily during the late 1960s through the
1970s. This engine belongs to the legendary “New Generation” engine
family that powered some of the most successful agricultural and
industrial machines of its era. The 6404 designation follows John
Deere’s engine naming convention: the first two digits indicate
displacement in cubic inches, while the last two digits denote the
number of cylinders.
The engine is renowned for its robust construction, featuring a
wet-sleeve cylinder design, seven main bearings, and a gear-driven
camshaft. Available in two primary variants - the naturally aspirated
6404D and the turbocharged 6404T - this powerplant offered farmers and
contractors a reliable, high-torque solution for heavy tillage, material
handling, and harvesting operations. Its long production run and
widespread application in tractors such as the John Deere 4020, 4230,
and 4430 have cemented its reputation as one of the most durable diesel
engines ever produced.
The John Deere 6404 engine represents a high-water mark in medium-duty
diesel design from the pre-electronic era. Its architecture prioritizes
low-speed torque, serviceability, and extreme longevity. The bore and
stroke dimensions of 4.25 inches by 4.75 inches create a heavily
undersquare configuration, which produces maximum torque at relatively
low engine speeds - a critical characteristic for drawbar pull and
PTO-driven implements.
The naturally aspirated 6404D, with a compression ratio of 16.5:1,
produces approximately 95-100 PTO horsepower and finds its home in
tractors like the John Deere 4020. The turbocharged 6404T, operating at
a reduced compression ratio of 15.5:1, raises output to 125-130 PTO
horsepower and powers later models such as the 4230 and 4430. The fuel
system employs a Roosa Master (Stanadyne) distributor-type injection
pump, a compact and reliable mechanical unit that delivers fuel to
open-chamber direct injectors.
The valvetrain uses pushrods and rocker arms actuated by a camshaft
located high in the cylinder block. The engine’s wet, replaceable
cylinder liners allow in-frame overhauls, a feature highly valued by
operators who demand thousands of hours of service before major repairs.
While heavy at approximately 1,250 pounds dry, the 6404 delivers a flat
torque curve and remarkable fuel efficiency for its era.
Engine Type: 4-cycle, Overhead Valve (OHV), Inline-6 diesel
Aspiration (6404D): Naturally Aspirated
Aspiration (6404T): Turbocharged (single exhaust-driven turbocharger)
Displacement: 404 cu.in (6.6 L)
Bore: 4.25 in (108 mm)
Stroke: 4.75 in (121 mm)
Compression Ratio (6404D): 16.5:1
Compression Ratio (6404T): 15.5:1
Firing Order: 1-5-3-6-2-4
Rotation (Facing Front/Fan): Clockwise
Rated Engine Speed: 2,200-2,500 rpm
Maximum No-Load Governed Speed: 2,550 rpm
Low Idle Speed: 650-750 rpm
PTO Horsepower (6404D, JD 4020): 95-100 hp (70.5-74 kW) @ 2,200 rpm
PTO Horsepower (6404T, JD 4430): 125-130 hp (92.5-96 kW) @ 2,500 rpm
Max Torque (6404D): 350-365 lb-ft (475-495 Nm) @ 1,400-1,600 rpm
Max Torque (6404T): 370-385 lb-ft (502-522 Nm) @ 1,500-1,700 rpm
The cylinder block is a deep-skirted, one-piece casting manufactured
from high-strength alloy cast iron. The block design incorporates
replaceable wet cylinder sleeves, which are in direct contact with the
engine coolant on their outer surfaces. Each of the six sleeves is
flange-mounted at the top and sealed at the bottom with multiple rubber
O-rings, preventing coolant from entering the crankcase. The wet-sleeve
arrangement provides excellent heat transfer from the combustion chamber
to the cooling system and enables complete engine rebuilding without
removing the crankshaft.
The block carries seven main bearing bulkheads, ensuring exceptional
crankshaft support under full load. The crankcase extends below the
crankshaft centerline, adding rigidity and reducing vibration. The
camshaft is mounted high in the left side of the block, driven by a gear
train at the front. Cast-in passages form the main oil gallery, running
the full length of the block. An integral timing gear housing is cast
into the front of the block. The block also features mounting pads for
the injection pump, water pump, and starter motor.
The cylinder head is a single, cast-iron cross-flow design. On the
naturally aspirated 6404D, the head features intake and exhaust ports
arranged to promote efficient airflow. On the turbocharged 6404T, the
head casting includes improved port geometry to accommodate higher
airflow from the turbocharger. Combustion chambers are of the
open-chamber, direct-injection type, machined directly into the cylinder
head face.
Each cylinder has two valves (one intake, one exhaust), arranged in a
straight line. Valves are made from heat-resistant silichrome steel,
with exhaust valves featuring stellite-faced tips and seats for enhanced
durability under high exhaust temperatures. Valve seats are
induction-hardened or fitted with replaceable hardened inserts. The
valvetrain operates via a gear-driven camshaft located in the block.
Mechanical lifters (solid tappets) follow the camshaft lobes and
transfer motion through hardened pushrods to cast-iron rocker arms.
The rocker arms pivot on a through-shaft mounted above the valves. Valve
lash adjustment uses a screw-and-locknut arrangement at the rocker
arm-to-valve stem interface. Valve adjustment is performed with the
engine at operating temperature. A steel-reinforced composite head
gasket seals each cylinder individually, with pressurized coolant and
oil passages routed through designated openings.
The fuel system is a mechanical direct-injection design comprising a
fuel transfer pump, a distributor-type injection pump, individual
high-pressure fuel lines, and multi-hole injection nozzles. A
diaphragm-type or gear-type transfer pump, mounted on the injection pump
body, draws fuel from the tank and delivers it to the injection pump at
low pressure.
The injection pump is a Roosa Master (Stanadyne) DB or CBC series
distributor pump, mounted on the left side of the engine block and
driven by the timing gear train. This pump houses a single pumping
plunger and a rotating distributor rotor. The rotor directs
high-pressure fuel to each cylinder in the correct firing sequence
(1-5-3-6-2-4). A mechanical centrifugal governor, internal to the
injection pump, maintains engine speed under varying loads by adjusting
fuel delivery. A manual shut-off lever stops the engine by cutting fuel
flow to the injectors.
High-pressure injection lines, constructed from steel tubing, connect
the injection pump outlets to the injectors. Each injector contains a
spring-loaded needle valve that opens at a precise pressure, atomizing
fuel directly into the combustion chamber. Injector opening pressure is
factory set between 3,000 and 3,500 psi (207-241 bar). Excess fuel not
injected returns to the tank through a return line.
The lubrication system is a pressurized, full-flow design using a
gear-type oil pump. The oil pump is mounted inside the oil pan on the
rear main bearing cap and is driven by the crankshaft via a hex drive
shaft. The pump draws oil through a screened pickup tube from the sump.
Oil passes through the pump and then through a full-flow spin-on oil
filter mounted externally on the engine block. A bypass valve within the
filter housing allows unfiltered oil to flow to the engine if the filter
becomes clogged.
From the filter, pressurized oil enters the main oil gallery, a
longitudinal passage drilled through the cylinder block. The main
gallery distributes oil to all seven main bearings through drilled
cross-passages. From the main bearings, oil travels through drilled
holes in the crankshaft to the six connecting rod bearings. A separate
gallery feeds oil to the camshaft bearings and to the mechanical
lifters.
The lifters direct oil upward through hollow pushrods to the rocker arms
and valve stems. Piston cooling jets, present on the turbocharged 6404T,
spray oil against the underside of each piston crown to manage thermal
loads. Oil pressure is regulated by a spring-loaded relief valve that
returns excess oil to the sump. The oil pan is a stamped steel or cast
aluminum design, available in different depths for various vehicle
applications.
The cooling system is a pressurized, thermostatically controlled
liquid-cooled design. Coolant circulation is driven by a belt-driven
centrifugal water pump mounted on the front of the cylinder block. The
water pump draws coolant from the bottom of the radiator and forces it
into the water jacket surrounding the wet cylinder sleeves. Coolant
flows upward around each sleeve and then into the cylinder head
passages, cooling the combustion chambers, valve seats, and injector
nozzles.
Heated coolant collects at the front of the cylinder head and passes
through the thermostat housing. The wax-pellet thermostat is rated to
begin opening at 180°F (82°C) and is fully open at 200°F (93°C). When
the thermostat is closed, coolant recirculates within the engine block
for rapid warm-up. When open, coolant flows to the top tank of the
radiator. On turbocharged 6404T engines, an additional coolant line
routes to the turbocharger bearing housing for thermal protection.
The radiator is a tube-and-fin, down-flow design with multiple rows of
cooling tubes. A gear-driven or belt-driven fan, mounted on the water
pump hub, pulls air through the radiator core. System pressure is
maintained by a radiator cap rated for 7-10 psi (0.5-0.7 bar), raising
the coolant boiling point. A coolant recovery reservoir is present on
most applications.
| Intake and Exhaust Systems |
Intake System: A dry-type, two-stage air cleaner with a replaceable
paper filter element and an integral dust ejector cleans intake air. On
the 6404T, the air cleaner outlet connects to the turbocharger
compressor inlet. The intake manifold distributes air evenly to all six
cylinders.
Exhaust System: A cast-iron exhaust manifold collects gases from all six
cylinders. On the 6404D, the manifold connects directly to a vertical
exhaust stack or muffler. On the 6404T, the manifold routes exhaust
gases into the turbocharger turbine housing, with a separate pipe
directing exhaust from the turbocharger outlet to the stack.
Starting System: The electrical starting system varies by application.
Early John Deere 4020 tractors used a unique 24-volt starting system
with two 12-volt batteries in series for cranking, combined with a
12-volt lighting system. Later 6404 applications use a 12-volt system
with a single, heavy-duty battery. The starter motor is a gear-reduction
or direct-drive unit engaging the flywheel ring gear. A starter solenoid
engages the drive pinion and closes the high-current circuit.
Governor System: A mechanical centrifugal governor is integral to the
injection pump. Flyweights inside the governor housing rotate with the
pump shaft. The operator’s throttle lever sets a spring force against
the governor. Any deviation from the desired engine speed changes the
centrifugal force on the flyweights, which moves a control sleeve and
rotates a metering valve within the injection pump. This system adjusts
fuel delivery on a cycle-by-cycle basis to maintain constant speed under
varying loads.
Turbocharger System (6404T Only): A single exhaust-driven turbocharger,
mounted on the exhaust manifold, compresses intake air before it enters
the cylinders. Exhaust gases flowing through the turbine housing spin a
turbine wheel connected via a common shaft to a compressor wheel. The
compressor draws ambient air through the air cleaner, compresses it, and
delivers it to the intake manifold. Compressed, heated air passes
through an optional air-to-air intercooler (charge air cooler) on some
industrial applications to increase density before entering the
cylinders.
Overall Engine Length (Front to Flywheel Housing): 43.0 in (1,092 mm)
Overall Engine Width: 24.0 in (610 mm)
Overall Engine Height (From Oil Pan to Valve Cover): 35.0 in (889 mm)
Dry Engine Weight (Complete, No Fluids, No Turbocharger): 1,250 lb (567
kg)
Dry Engine Weight (6404T with Turbocharger and Intercooler): 1,330 lb
(603 kg)
Engine Oil:
Grade: SAE 15W-40 (diesel-rated, API CC or CD)
Oil Capacity (Shallow Sump): 12.0 U.S. quarts (11.4 L)
Oil Capacity (Deep Sump): 16.0 U.S. quarts (15.1 L)
Normal Oil Pressure (Rated Speed): 35-50 psi (241-345 kPa)
Minimum Oil Pressure (Hot Idle): 10 psi (69 kPa)
Engine Oil Change Interval: Change every 150 operating hours or
annually.
Oil Filter Change Interval: Replace at every oil change (full-flow
spin-on filter).
Cooling System:
Coolant Type: Diesel-rated ethylene glycol antifreeze (50/50 mix with
distilled water).
Total System Capacity: 24-28 U.S. quarts (22.7-26.5 L).
Thermostat Opening Temperature: 180°F (82°C).
Radiator Cap Pressure Rating: 7-10 psi (0.5-0.7 bar).
Valve Lash (Hot - Intake): 0.014 in (0.36 mm).
Valve Lash (Hot - Exhaust): 0.014 in (0.36 mm).
Valve Adjustment Interval: Inspect and adjust every 1,000 operating
hours.
Fuel Filter Change Interval: Replace fuel filters every 300 hours or at
engine oil change.
Injector Opening Pressure: 3,000-3,500 psi (207-241 bar). Recalibrate
every 1,500 hours.
Air Cleaner Service: Replace primary paper element every 250 hours.
Cylinder Head Bolts: Final torque 150 lb-ft (203 Nm).
Connecting Rod Cap Nuts: 95 lb-ft (129 Nm).
Main Bearing Cap Bolts: 150 lb-ft (203 Nm).
Flywheel Bolts: 115 lb-ft (156 Nm).
Crankshaft Pulley/Damper Bolt: 200-220 lb-ft (271-298 Nm).
Rocker Arm Shaft Bracket Bolts: 40 lb-ft (54 Nm).
Intake Manifold Bolts: 25-30 lb-ft (34-41 Nm).
Exhaust Manifold Nuts (6404D): 30-35 lb-ft (41-47 Nm).
Turbocharger Mounting Nuts (6404T): 35-40 lb-ft (47-54 Nm).
Injection Pump Mounting Nuts: 25 lb-ft (34 Nm).
High-Pressure Fuel Line Fittings (Injector End): 25 lb-ft (34 Nm).
Oil Pan Bolts (Stamped Steel Pan): 12-15 lb-ft (16-20 Nm).
Valve Cover Bolts: 7-9 lb-ft (9.5-12 Nm).
Thermostat Housing Bolts: 18-22 lb-ft (24-30 Nm).
Water Pump Mounting Bolts: 25-30 lb-ft (34-41 Nm).
Starter Motor Mounting Bolts: 45-50 lb-ft (61-68 Nm).
Oil Drain Plug: 30-40 lb-ft (41-54 Nm).
The John Deere 6404 engine was utilized across a wide range of
agricultural, industrial, and harvesting equipment throughout the 1960s
and 1970s.
Agricultural Tractors:
John Deere 4020 (naturally aspirated 6404D).
John Deere 4230 (turbocharged 6404T).
John Deere 4430 (turbocharged 6404T).
John Deere 4520 (turbocharged 6404T, higher fuel setting).
Self-Propelled Harvesting Equipment:
John Deere 6600 Combine (naturally aspirated or turbocharged).
John Deere 7700 Combine (turbocharged 6404T).
Industrial Equipment:
John Deere 644 Series Wheel Loaders (turbocharged 6404T).
John Deere 690 Series Excavators (turbocharged 6404T).
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