4WD HONDA CR-V 1998 RD1-RD3 / 1.G Service Manual

Description
Rear Differential
Outline
The Real-time 4WD-Dual Pump System model has a hydraulic clutch and a differential mechanism in the rear differential
assembly. Under normal conditions, the vehicle is driven by the front wheels. However, depending on to the driving force
of the front wheels and the road conditions. the system instantly transmits appropriate driving force to the rear wheels
without requiring the driver to switch between 2WD (tront wheel drive) and 4WD (four wheel drive). The switching mecha-
nism between 2WD and 4WD is integrated into the rear differential assembly to make the system light and compact.
ln addition, the dual-pump system switches off the rear-wheel-drive force when braking in a forward gear. This allows the
braking system to work properly on models equipped with an Anti-lock Braking System (ABS).
Construction
The rear differential assembly consists of the torque control differential case assembly and the rear differential carrier
assembly. The torque control differential case assembly consists of the differential clutch assembly, the companion
flange, and the oil pump body assembly. The rear differential carrier assembly consists of the differential mechanism. The
differential drive and driven gears are hypoid gears.
The oil pump body assembly consists of the front oil pump, the rear oil pump, the hydraulic control mechanism, and the
clutch piston. The clutch piston has a disc spring that constantly provides the differential clutch assembly with a preset
torque to Drevent abnormal sound.
The clutch guide in the differential clutch assembly is connected to the propeller shaft via the companion flange, and it
receives the driving force lrom the transfer assembly. The clutch guide rotates the clutch plate and the front oil pump in
the oil pump body.
The clutch hub in the differential clutch assembly has a clutch disc that is splined with the hypoid drive pinion gear. The
hypoid drive gear drives the rear oil pump.
The front and rear oil pumps are trochoidal pumps. The rear oil pump capacity is 2.5 percent larger that the front oil pump
to handle the rotation difference between the front and rear wheels caused by worn front tires and tight corner braking.
The oil pumps are designed so the fluid intake works as a fluid discharge when the oil pumps rotate in reverse. Genuine
Honda CVT fluid is used instead of differential fluid.
Operation
When there is a difference in rotation speed between the front wheels (clutch guide) and rear wheels (hypoid driven gear),
hydraulic pressure from the front and rear oil pumps engages the differential clutch, and drive force from the transler
assembly is applied to the rear wheels.
The hydraulic pressure control mechanism in the oil pump body selects 4WD mode when the vehicle is started abruptly,
or when accelerating in a forward or reverse gear (causing rotation difference between the front and rear wheels). or
when braking in reverse gear {when decelerating). lt switches to 2WD mode when the vehicle is driven at a constant speed
in forwar! or reverse gear (when there is no rotation difference between the front and rear wheels), or when braking in a
fo rwa rd gear (when decelerating).
To protect the system, the differential clutch assembly is lubricated by hydraulic pressure generated by the oil pumps in
both 4WD and 2WD modes. Also, the thermal switch relieves the hydraulic pressure on the clutch piston and cancels 4WD
mode if the temDerature of the differential fluid rises above normal.
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Description
Hydraulic Flow
Forward Start and Acceleration l4WD)During a forward start and forward acceleration, the dual pump system can engage four wheel drive.lf the front wheels spin faster than the rear wheels, the front oil pump spins faster than the rear oil pump. The front pump
draws fluid through check valve B and discharges it. Some of the discharged fluid is drawn in the by the rear oil pump.The remaining fluid will pass through check valve E into the clutch piston. There, hydraulic pressure is regulated by twoorifices.
The regulated hydraulic pressure at the clutch piston pushes the plates and discs of the clutch together to form a connec-tion. The engaged clutch then passes driving force from the transfer assembly to the rear wheels, producing 4WD.
oRrFtcEsFRONT OIL PUMPREAR OIL PUMP
Forward Driving at Constant Speed lzWD)When driving forward at a constant speed (cruising), the dual pump system functions in two wheel drive mode.The rotation speed of the front and rear wheels is the same, so the speed of the front and rear pumps is also the same.Fluid discharged by the front oil pump is drawn in by the rear oil pump and is circulated through the system. Becausethere is no pressure built up at the clutch piston, the clutch does not engage, and the vehicle remains in 2WD (front wheeldrive).
FRONT OIL PUMP
15-6
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Forward Deceleration l2WDl
During forward deceleration, the dual pump system functions in two wheel drive mode.
Because of braking characteristics, the speed of the rear wheels may exceed the speed ol the front wheels during deceler-
ation. lf so, the rear oil pump spins faster than the front oil pump.
Fluid discharged by the rear oil pump is simply drawn in again by the rear pump and recirculated. Because there is no
pressure built up at the clutch piston. the clutch piston does not engage, and the vehicle remains in 2WD (front wheel
drive).
Reverse Start and Acceleration (4WD)
During reverse start and reverse acceleration, the dual pump system can engage four wheel drive.
lf the front wheels spin faster than the rear wheels, the front oil pump spins faster than the rear oil pump. The front oil
pump draws in fluid through check valve A and discharges it. {Note that in reverse, the direction of the pumps is the oppo-
site of that during forward driving.)
Some of the fluid that is discharged by the front oil pump is drawn in by the rear oil pump. The remaining fluid passes
through check valve F into the cylinder of the clutch piston, where it is regulated by two orifices.
The regulated hydraulic pressure at the clutch piston may force the plates and discs of the clutch together to form a con-
nectlon. The engaged clutch passes driving force from the transfer assembly to the rear wheels, producing 4WD.
oRtFtcEsFRONT OIL PUMP
{cont'd)
15-7
REAR OIL PUMP
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Description
Hydraulic Flow (cont'dl
Reverse Driving at Constant Speed l2WD)when driving in reverse at a constant speed, the dual pump system functions in two wheel drive mode.The rotation speed of the front and rear wheels is the same, so the speed of the front and rear pumps is also the same,Fluid discharged by the front oil pump is drawn in by the rear oil pump and is circulated through the system. But, becausethe there is a difference in the capacity between the two pumps, fluid flows through check valve E, and then through ori-Iices. This fluid lubricates and cools the clutch assembly and bearings.ls this condition, only a low pressure is built up at the clutch piston. Therefore the clutch does not engage, and the vehicleremains in 2WD (front wheel drive).
Reverse Deceleration l/tWDl
During reverse deceleration, the dual pump system can engage four wheel drive.When decelerating in reverse direction, the speed of the rear wheels may exceed the speed of the front wheels (due toengine braking). In this condition, the rear oil pump draws fluid through check valves B and C. Fluid discharged from therear oil pump then flows through check valve E to the clutch piston. There, pressure is regulated by two orifices.The regulated hydraulic pressure at the clutch piston may force the plates and discs of the clutch together to form a con,nection. The engaged clutch passes driving force from the transfer assembly to the rear wheels, producing 4WD.
oRtFtcEsREAR OIL PUMP
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Thermal Switch Operation l2WD)
During 4WD operation, pressure-regulated fluid is in contact with the clutch piston and the thermal switch.
lf the temperature of the fluid in the differential goes too high, the thermal switch pushes open the relief valve R. This
causes the pressure in the clutch piston to drop, and 4WD mode is disengaged.
THERMAL SWITCHRELIEF VALVE
Reliet Valve Operation
When the fluid pressure goes higher than the relief valve spring force, check valve R opens. Pressure applied at the clutch
piston is held constant. This feature adds stability by preventing the rear wheel drive system from experiencing excessive
to rque.
RELIEF VALVE
15-9
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Real-time 4WD-Dual Pump System
Troubleshooting (Automatic Transmissionl
When starting and accelerating in forward gesrs {4WDmodel
1. Lift up the vehicle so all four wheels are off theground (see section 1).
2. Make a mark on either No.
shaft.
'I or No.2 propeller
PROPELLER SHAFT
Start the engine, and let it run until it warms up (the
radiator fan comes on at least twice).
With the engine at idle. shift to the E position.
Apply the parking brake firmly. and measure thetime it takes the propeller shaft to rotate 10 times.. lf the measured time is more than 10 seconds,
the 4WD system is normal.
. lf the time is less than 10 seconds, there is aproblem in 4WD system. Check the differential
fluid. lf the differential fluid is normal, replace
the torque control differential case kit.
15-10
When starting and accelerating in revGrsg gear {4WDmodel
1. Lift up the vehicle so all four wheels are off theground (see section 1).
Make a mark on either No.
shaft.
1 or No. 2 propeller
PROPELLER SHAFT
Start the engine. and let it run until it warms up (the
radiator fan comes on at least twicei.
With the engine at idle, shift to the E position.
Apply the parking brake firmly, and measure the
time it takes the proDeller shaft to rotate 10 times,. lf the measured time is more than 10 seconds,
the 4WD system js normal.. lf the time is less than 10 seconds, there is aproblem in 4WD system. Check the differential
fluid. lf the differential fluid is normal, reolace
the torque control differential case kit.
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Troubleshooting (Manual Transmissionl
When starting and accelerating in forward gears (4WD
mode)
1. Lift up the vehicle so all four wheels are off the
ground {see section 1)
3.
Start the engine, and let it run until it warms up (the
radiator fan comes on at least twlce).
With the engine at idle, shift into 1st gear and
release the clutch.
Apply the parking brake firmlY
. lf the engine stalls, the 4WD system is normal.
. lf the engine continues running, there is a prob-
lem in 4WD system. Check the differential fluid. lf
the differential fluid is normal, replace the torque
control ditferential case kit.
2.
When starting and accelerating in reverse gear (4WD
model
1. Lift up the vehicle so all four wheels are off the
ground (see section 1).
Start the engine, and let it run until it warms up (the
radiator fan comes on at least twice)
With the engine at idle, shift into reverse gear and
release the clutch.
Apply the parking brake firmlY
. lf the engine stalls, the 4WD system is normal.
. lf the engine continues running, there is a prob-
lem in 4WD system. Check the differential fluid lf
the differential fluid is normal, replace the torque
control differential case kit.
3.
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Real-time 4WD-Dual Pump System
Troubleshooting (Automatic Transmission/Manual Transmission)
Whon d6c6l6rating in a torward gear {2WD mode}
1. Block the front wheels, raise the left rear wheel. and
support it with a safety stand as shown.
Hold the tire and turn it counterclockwise continu-
ouslv for more than one rotation.
lf the rotation of the wheel does not gradually
feel heavy while rotating, the 2WD system when
decelerating in a forward gear is normal.
lf the rotation of the wheel gradually feels heavy,
there is a problem in the system. Check the dif-
ferential fluid, lf the fluid is normal, reDlace the
toroue control differential case kit.
WHEEL CHOCKS
15-12
When decelerating in reverse gear (4WD mod€)
1. Block the front wheels. raise the left rear wheel, and
suppo( it with a safety stand as shown.
Hold the tire and turn it clockwise continuouslv for
more than one rotation.
lf the rotation of the wheel gradually feels heaw.
the 4WD system when decelerating in reverse gear
is normal,
lf the rotation of the wheel does not gradually feel
heavy, there is a problem in the system. Check
the differential fluid. lf the fluid is normal.
reolace the torque control differential case kit,
WHEEL CHOCKS
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Rear Differential AssemblY
Troubleshooting
Most problems in the unit are to be diagnosed by identifying noises from the gears or bear'ngs'
care should be taken during diagnosis not to confuse differential noises with those from other drivetra'n components'
SymptomProbable CauseRemedy
Will not go into 4WD mode. Fluid level too low
. Incorrect fluid type
. Add fluid. Replace
Will not return to 2WD modeIncorrect fluid typeDrain and fill the differential
Gear or bearing noisesFluid level too low
Incorrect fluid type
Damaged or chipped gears
Add fluid
Drain and fill the differential
Replace the differential carrier
assemory
Overheating. Fluid leveltoo low
. Incorrect fluid type
. Add fluid. Drain and fill the differential
Fluid leakFluid level too high
Clogged breather hose
Worn or damaged oil seal
Damaged sealing washer
Loose mounting bolts or inade-
quate sealing
Lower to proper level
Clean or replace
Replace
Replace
Recheck torque or aPPIY sealant
15-13
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Maintenance
Differential Fluid
!@ Make sure lifts are placed properly lseesection 1).
1. With the vehicle on level ground, inspect differential
fluid with engine OFF.
2. Remove the oil filler plug, then check the level andcondition of the fluid.
Proper Level
o|I FII.IIR PI-UG4t N.m la.8 kgl.m, 35 lbl.ftl
The fluid level must be up ro the fill hole. lf it isbelow the hole, add the recommended fluid until itruns out, then reinstall the oil filler plug with a new
wasner.
lf the differential tluid is dirty, remove the drainplug, and drain the fluid.
4.
DMIN PLUGa7 N.m 14.8 kgl.m, 35 lbt.ftl
15-14
Clean the drain plug, then reinstall it with a new
washer, and refill the differential with the recom-
mended fluid to the proper level.
NOTEr lf you disassembly the differential, check thefluid level again after the 4WD system check is fin-
ished. Add fluid if necessary.
Reinstall the oil filler plug with a new washer.
Fluid Capacity
1.0 / {1.1 US $, 0.9 lmp qt) at tluid change
1.2 / {1.3 US $, 1.1 lmp qt) at oyerhaul
Recommended fluid:
Genuine Honda CVT Fluid
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