sensor ACURA NSX 1991 Service Owner's Manual

Transmission Assembl y
Removal
Make sur e lift s ar e place d properly , an d
hois t bracket s ar e attache d t o correc t position s (se e
sectio n 1 ).
CAUTION : Us e fende r cover s t o avoi d damagin g
painte d surfaces .
1 . Chec k an d recor d th e rea r whee l alignmen t (se e
sectio n 18 ).
2 . Disconnec t th e batter y negativ e (- ) an d positiv e (+ )
cable s fro m th e battery .
3 . Drai n transmissio n oil . Reinstal l th e drai n plu g wit h
a ne w washer .
Corrosio n resistan t bolt/nu t
4. Remov e th e stru t bar .
5 . Remov e th e ai r cleane r assembly .
6 . Remov e th e connector s fro m th e contro l box , an d
remov e th e contro l box .
CAUTION : D o no t remov e th e vacuu m tube s fro m
th e contro l box .
7 . Remov e th e wir e harnes s holder , jumpe r connecto r
an d transmissio n ground cable.
8 . Disconnec t th e back-u p ligh t switch , neutra l posi -
tio n switch , differentia l spee d sensor , an d vehicl e
speed senso r (VSS ) connectors .
9. Disconnec t th e starte r moto r cables , the n remov e
th e starte r motor .
10 . Remov e th e transmissio n mount .
11 . Remov e th e tw o transmissio n housin g bolts .
TRANSMISSIO N
HOUSIN G BOLT S
CONTROL BO X
BACK-U PLIGHT SWITC H
CONNECTO R
WIR E HARNES S HOLDE R
STARTER MOTOR
CABLES
NEUTRA L
POSITIO N
SWITCHCONNECTO R
DIFFERENTIA L
SPEE D SENSO R
VEHICL E SPEE D
SENSO R (VSS )
CONNECTO R
JUMPERCONNECTO R
TRANSMISSIO N
MOUNTING BOLT S
TRANSMISSIO NHANGER
STARTE RMOTOR MOUNTIN
G TRANSMISSIO N
BOLT S MOUN T
TRANSMISSIO
N
GROUN D
CABLE
ProCarManuals.com

Transmission Assembly

Removal

20. Remove the intermediate shaft heat cover and the intermediate shaft mounting bolts.
21. Pry the intermediate shaft out of the differential. Pull and remove it. NOTE:
• Coat all precision finished surfaces with clean engine oil or grease.
• Tie plastic bags over the driveshaft ends.

Corrosion resistant bolt/nut
INTERMEDIATE SHAFT
SUPPORT BASE
INTERMEDIATE SHAFT INTERMEDIATE SHAFT
HEAT COVER
INTERMEDIATE SHAFT
MOUNTING BOLT
22. Remove the parking brake cable holder and the wheel sensor wire clamp.
23. Remove the bolt, and separate the toe control arm from the side beam (see section 18).
24. Remove the damper fork bolt (see section 18).
25. Remove the bolts, and separate the lower control arm from the side beam. 26. Pry the driveshaft out of the differential. Pull and remove it. NOTE:
• Coat all precision finished surfaces with clean engine oil or grease.
• Tie plastic bags over the driveshaft ends.

Corrosion resistant bolt/nut
DAMPER FORK BOLT SELF-LOCKING NUT

Replace.

TOE CONTROL ARM
WHEEL SENSOR WIRE CLAMP PARKING BRAKE
CABLE HOLDER
FLANGE BOLT
LOWER CONTROL ARM SELF-LOCKING NUTReplace. ADJUSTING

BOLT
ADJUSTING

CAM
SELF-LOCKING NUT

Replace.
SET RING

Replace.ProCarManuals.com

Transmission Housing

Removal

NOTE: Place the clutch housing on two pieces of wood

thick enough to keep the mainshaft from hitting the

workbench.

1. Remove the back-up light switch, neutral position

switch, differential speed sensor and vehicle speed

sensor (VSS).

VSS

(O-RING Replace.)
NEUTRAL

POSITION

SWITCH

DIFFERENTIAL

SPEED SENSOR

BACK-UP LIGHT SWITCH

2. Remove the sealing bolts, springs and steel balls.

3. Remove the transmission housing attaching bolts

in a crisscross pattern in several steps.

4. Remove the 36 mm sealing bolt.

SPRING

(L. 25 mm)

ATTACHING

BOLT
.14 mm SEALING BOLT

36 mm SEALING BOLT

STEEL BALL (3/8 in)

12 mm SEALING

BOLT

16 mm SEALING

BOLT COMP
5. Expand the snap ring on the countershaft ball bear-

ing, and remove it from the groove using a pair of

snap ring plier.

SNAP RING PLIER

SNAP RING

6. Separate the clutch housing from the transmission

housing.

7. Remove the thrust shim and oil guide plate from the

transmission housing.

THRUST SHIM

OIL GUIDE

PLATE

TRANSMISSION HOUSING
SPRING

(L.
24.2
mm)

STEEL

BALLS (5/16 in)ProCarManuals.com

28. Instal l th e transmissio n moun t an d tw o transmissio n
housin g mountin g bolts .
29 . Instal l th e starte r motor , an d connec t th e starte r
motor cables .
NOTE: Whe n installin g th e starte r moto r cable ,
mak e sur e tha t th e crimpe d sid e o f th e rin g termi -
nal s facin g ou t (se e sectio n 23 ).
30 . Instal l th e transmissio n groun d cabl e an d jumpe r con -
nector , an d connec t th e back-u p ligh t switch , neu -
tra l positio n switch , differentia l spee d sensor , an d
vehicl e spee d senso r (VSS ) connector . 31
. Instal l th e contro l box , an d connec t th e contro l bo x
connectors .
32. Instal l th e ai r cleane r assembly .
33. Instal l th e stru t bar .
34 . Refil l th e transmissio n wit h oi l (se e pag e 13-3 ).
35 . Connec t th e batter y positiv e ( + ) an d negativ e (- )
cable s t o th e battery .
36 . Inspec t th e rea r cambe r (se e sectio n 18 ).
37 . Chec k th e clutc h operation .
38 . Shif t th e transmission , an d chec k fo r smoot h opera -
tion.
Corrosio n resistan t bolt/nu tTRANSMISSIO N HOUSIN GMOUNTING BOLT S12 x 1.2 5 mm65 N- m (6. 5 kg-m , 4 7 Ib-ft )
CONTROL BO X
BACK-U P LIGH TSWITC HCONNECTO R
WIR E
HARNES S
HOLDE R
NEUTRA L
POSITIONSWITCHCONNECTO R
STARTE R
MOTORCABLE S DIFFERENTIA
L
SPEE D SENSO R
VSSCONNECTO R
JUMPE R
CONNECTO R
TRANSMISSIO N MOUNTIN GBOLT
TRANSMISSIO N MOUNTIN GBOLTS10 x 1.2 5 mm60 N- m (6. 0 kg-m , 4 3 Ib-ft )
12 x 1.2 5 mm95 N- m (9. 5 kg-m . 6 9 Ib-ft )
12 x 1.2 5 mm75 N- m (7. 5 kg-m , 5 4 Ib-ft )
12 x 1.2 5 mm75 N- m (7. 5 kg-m , 5 4 Ib-ft )
TRANSMISSIO NGROUND CABL E
ProCarManuals.com

Driveshafts
Removal
6. Remov e th e whee l senso r fro m th e knuckl e an d th e
rea r o f th e lowe r arm , the n secur e th e whee l senso r
wir e t o th e suspensio n arm .
NOTE :
• D o no t disconnec t th e whee l sensor .
• Avoi d twistin g th e wire s whe n reinstallin g th e
whee l sensor .
7 . Disconnec t th e parkin g brak e cabl e fro m th e body .
Corrosio n resistan t bol t
8 m m FLANG E BOLT S
2 2 N- m (2. 2 kg-m , 1 6 Ib-ft ) PARKIN
G BRAK E CABL E
WHEE L SENSO R 6 mm BOLT-WASHE R
1 0 N- m (1. 0 kg-m , 7 Ib-ft )
8 m m BOLT-WASHE R
2 2 N- m (2. 2 kg-m , 1 6 Ib-ft )
Corrosio n resistan t bol t
TO E CONTRO L AR M FLANG
E BOL T
12 x 1.2 5 mm95 N- m (9. 5 kg-m , 6 9 Ib-ft )
9. Hol d th e dampe r lowe r moun t o f stabilize r lin k wit h
a wrench , an d remov e th e dampe r mountin g nut .
10. Hol d th e bal l pi n o f th e stabilize r lin k wit h a he x
wrench , an d loose n th e self-lockin g nut .
Corrosio n resistan t nu t
DAMPE R MOUNTIN G NU T
12 x 1.2 5 mmReplace .
9 5 N- m (9. 5 kg-m , 6 9 Ib-ft )
WRENC H
HE X WRENC H
STABILIZE R LIN K
SELF-LOCKIN G NU T
12 x 1.2 5 mmReplace .85 N- m (8. 5 kg-m , 6 1 Ib-ft )
11. Remov e th e self-lockin g nut , the n remov e th e
stabilize r lin k fro m th e stabilize r ba r an d knuckle .
Corrosio n resistan t nu t
REA R DAMPE R
SELF-LOCKING NU T
12 x 1.2 5 mmReplace .
STABILIZE R LIN K
8. Remov e th e flang e bolt , the n disconnec t th e to e
contro l ar m fro m th e body .
ProCarManuals.com

Electrical Power Steering (EPS)

Outline

The NSX/NSX-T uses an electric motor-driven power steering, which possesses the characteristics best suited for a mid-

engine automobile. This system is a power-assisted steering device, with a motor inside the steering gearbox driven by

the EPS control unit. Its distinctive features are described below:

• Minimized loss of engine horsepower and decreased fuel consumption.

• A linear steering feel and the reduction of kickback.

• The system is compact and lightweight because it requires no complicated hydraulic piping, etc.

ALTERNATOR

TRANSMISSION

CONTROL MODULE (TCM)

EPS CONTROL UNIT

VEHICLE

SPEED SENSOR

PULSE UNIT (MT)

BATTERY

STEERING GEARBOX
STEERING WHEEL

STEERING

COLUMNProCarManuals.com

System Description

Major Components

The Electrical Power Steering system is composed of the following major components:

• A steering gearbox that converts rotary operation of the steering wheel into transverse operation via a rack and pinion

mechanism. Steering sensors and an actuating motor are incorporated.

• A control unit that computes the optimum amount of power assistance, taking into account steering torque, steering

speed, and vehicle speed. Self-diagnosis functions are included.

• A power unit that drives the motor according to the signals from the EPS control unit. A current sensor is built in to

give feedback information to the EPS control unit. Two relays shut off the power if a problem in the system occurs.

• The countershaft speed sensor on the automatic transmission or the differential speed sensor on the manual transmis-

sion sends a vehicle speed signal to the EPS control unit. Also the speedometer sends a vehicle speed signal to the EPS

control unit. The two signals are used as a double-check.ProCarManuals.com

System Operation

Manual Steering Operation

Steering wheel input rotates the pinion of the gearbox through a universal joint. Due to the rack and pinion mechanism,

the rotation of pinion is converted into a transverse motion at the rack, which steers the front wheels throught the tie-rods

and knuckles the same as an ordinary rack and pinion system.

Assisting Operation

In addition to the manual steering operation, the steering sensor on the pinion shaft transmits a signal to the EPS control

unit when it receives a steering input. The EPS control unit calculates an adequate motor control with addition of vehicle

speed signals. Based on the signal from the sensors, the EPS control unit drives the motor inside the gearbox. The torque

generated by the motor is transmitted to a ball screw, through gears, and converted into an assisting thrust in the axial

direction of rack. The assisting thrust acts in the steering direction and lessens the steering force required at the steering

wheel.

EPS CONTROL UNIT

RECIRCULATING

BALL SCREW

STEERING WHEEL
RACK

STEERING SENSOR

(Build in the rotation sensor

and torque sensor)

MOTOR

STEERING GEARBOXProCarManuals.com

System Description

Function and Operation

Steering Sensor

The steering sensor consists of a torque sensor, an

interface, and the rotation sensor.

Torque Sensor

The torque sensor converts steering torque input and its

direction to voltage signals, in conjunction with the

interface.

A torsional force caused by steering operation is con-

verted to an axial movement of a slider core. A variable

differential transformer is installed around the slider

core.

Within the transformer are three coils, a primary coil on

the inside, and two secondary coils, one for right turns

and one for left turns.

Alternating current is passed through the primary coil

when the system is energized. The amount of mutual

induction from the primary coil to the secondary coils

changes depending on the position of the slider coil.

The input shaft and the slider are one piece. Rotation of

the shaft moves the slider in a circular direction. The

pinion is turned via the torsion bar. The slider core is

installed on the pinion shaft on grooves, and turns with

the pinion shaft.

When there is little resistance, the input shaft torsion

bar, pinion shaft, and the slider core turn together to the

same angle. The slider core does not move up/down.
TORSION BAR

INPUT

SHAFT

INTERFACE

CIRCUIT

SPIRAL

GROOVE

ROTATION

SENSOR

GUIDE

PIN

TRANSFORMER

PINION GEAR

WING

When there is resistance on the input shaft (hard to steer situation), and the slider pin is turned at an angle by the steering

wheel, the torsion bar is twisted due to the resistance. Accordingly, the pinion shaft turns at a smaller angle. The differ-

ence in the turning angles changes the position of the slider pin in the groove, forcing the slider core upward or down-

ward, depending on the direction of the direction of the turn.

PRIMARY COIL

UPPER SECONDARY COIL

LOWER SECONDARY COIL

SLIDER
SLIDERProCarManuals.com

Rotation Sensor

The rotation sensor is housed inside the steering gearbox near the pinion. It converts the rotation speed and direction of

steering into voltage signals. The rotation of the steering wheel is transmitted to the pinion, which drives the sensor by

accelerating its speed through the three pieces of transmission the gears. Acting as a kind of direct current generator, the

sensor generates direct current voltage proportionately with the rotational speed of the pinion. When the steering direc-

tion is reversed, the voltage is generated in the opposite direction. No power is generated when driving straight ahead

without turning the steering wheel.

Interface Circuit

The interface circuit is housed inside the steering gearbox near the pinion. It rectifies and amplifies the signals from the

torque sensor and the rotation sensor, and transmits the steering signals to the EPS control unit. A phase compensating

circuit is also built in, which changes the output signals in accordance with the drive signals input from the EPS control

unit.

TRANSMISSION GEARS

INTERFACE CIRCUIT

ROTATION SENSORProCarManuals.com