ACURA NSX 1991 Service Repair Manual

Power Flow

MAINSHAFT REVERSE GEAR
MAINSHAFT 1ST GEAR

1ST CLUTCH

1ST-HOLD CLUTCH

ONE-WAY CLUTCH COUNTERSHAFT 1ST GEAR PARKING GEAR
COUNTERSHAFT REVERSE GEAR COUNTERSHAFT 4TH GEAR
2ND CLUTCH
SECONDARY SHAFT 2ND GEAR SECONDARY SHAFT 3RD GEAR FINAL DRIVEN GEAR
(cont'd)

FINAL DRIVE GEAR
TORQUE CONVERTER
3RD CLUTCH
COUNTERSHAFT
3RD CLUTCH COUNTERSHAFT
2ND GEAR
4TH CLUTCH

MAINSHAFT

3RD GEAR

MAINSHAFT

4TH GEAR

O: Operates, x : Doesn't operate.

Although the 1st clutch engages, driving power is not transmitted as the one-way clutch slips.ProCarManuals.com

Description

Power Flow (cont'd)

Position

At position, hydraulic pressure is applied to the 1st clutch and to the 1st-hold clutch.

The power flow when accelerating is as follows;

1. Hydraulic pressure is applied to the 1st clutch on the mainshaft and power is transmitted via the 1st clutch to the

mainshaft 1st gear.

2. Power transmitted to the mainshaft 1st gear is conveyed via the countershaft 1st gear to the one-way clutch on

the inside of the countershaft 1st gear. The one-way clutch is used to drive the countershaft.

3. Power is transmitted to the final drive gear and drives the final driven gear.

Hydraulic pressure is applied to the 1st-hold clutch but the countershaft is rotated by the one-way clutch.

The power flow when decelerating is as follows;

1. Rolling resistance from the road surface through the rear wheels to the final drive gear, then to the countershaft

1st gear via the Ist-hold clutch which is applied during deceleration.

2. The one-way clutch becomes free at this time because of the countershaft rotates in reverse at the time of accelerating.

3. The counterforce conveyed to the countershaft 1st gear turns the mainshaft 1st gear. At this time, since hydraulic

pressure is also applied to the 1 st clutch, counterforce is also transmitted to the mainshaft. As a result, engine braking

can be obtained with 1st gear.

1ST CLUTCH

MAINSHAFT 1ST GEAR

MAINSHAFT
TORQUE CONVERTER

COUNTERSHAFT

FINAL DRIVEN GEAR
1ST-HOLD CLUTCH

COUNTERSHAFT 1ST GEAR

ONE-WAY CLUTCH

FINAL DRIVE GEARProCarManuals.com

1. Power from the mainshaft 3rd gear drives the countershaft 3rd gear. Since at this time there is no hydraulic pressure

to the 3rd clutch. The countershaft 3rd gear turns freely and drives the secondary shaft 3rd gear.

2. The power is also transmitted to the secondary shaft 2nd gear because hydraulic pressure is applied to 2nd clutch.

3. The secondary shaft 2nd gear drives the countershaft 2nd gear. Power is transmitted to the final drive gear and

drives the final driven gear.

1ST CLUTCH

MAINSHAFT 3RD GEAR
MAINSHAFT 3RD GEAR

MAINSHAFT

COUNTERSHAFT

FINAL DRIVE GEAR

(cont'd)
FINAL DRIVEN GEAR
SECONDARY SHAFT 3RD GEAR
SECONDARY SHAFT 2ND GEAR
2ND CLUTCH
SECONDARY SHAFT
ONE-WAY CLUTCH
Position is provided to drive only in 2nd speed.

TORQUE CONVERTER
NOTE:

At position, hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of the 2nd gear

exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.

Power flow in position, 2nd speed is the same as position.ProCarManuals.com

Description

Power Flow (cont'd)

2. Power is transmitted to the final drive gear and drives the final driven gear.

MAINSHAFT 1ST GEAR

1ST CLUTCH

MAINSHAFT 3RD GEAR

MAINSHAFT
TORQUE CONVERTER

COUNTERSHAFT

FINAL DRIVE GEAR

FINAL DRIVEN GEAR
3RD CLUTCH
COUNTERSHAFT 3RD GEAR
ONE-WAY CLUTCH
Position is provided to drive only in 3rd speed.

At 3 position, hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of the 3rd gear

exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.

Power flow in position, 3rd speed is the same as position.ProCarManuals.com

In position, the optimum gear is automatically selected from the gear ratios of 1st, 2nd 3rd and 4th speeds, according
to conditions such as the balance between throttle opening (engine load) and vehicle speed.
1ST CLUTCHMAINSHAFT 1ST GEAR
MAINSHAFT
TORQUE CONVERTER
COUNTERSHAFT
FINAL DRIVE GEAR
(cont'd)
FINAL DRIVEN GEAR

PARKING GEAR

COUNTERSHAFT

1ST GEAR

ONE-WAY CLUTCH
Position, 1st speed
1 . Hydraulic pressure is applied to the 1st clutch, which rotates together with the mainshaft, and the mainshaft 1st gear rotates.
2. Power is transmitted to the countershaft 1st gear, and drives the countershaft via the one-way clutch.
3. Power is transmitted to the final drive gear and drives the final driven gear. NOTE: In the position, hydraulic pressure is not applied to the 1st-hold clutch.ProCarManuals.com

Description

Power Flow (cont'd)

1 . Hydraulic pressure is applied to the 4th clutch, which rotates together with the mainshaft, and the mainshaft 4th

gear rotates.

2. Power is transmitted through countershaft 4th gear to the countershaft.

3. Power is transmitted to the final drive gear and drives the final driven gear.

NOTE: At position, 4th speed, hydraulic pressure is also applied to the 1 st clutch, but since the rotation speed of

4th gear exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.

1ST CLUTCH

MAINSHAFT

1ST GEAR
MAINSHAFT

4TH GEAR

4TH CLUTCH

MAINSHAFT
TORQUE CONVERTER

COUNTERSHAFT

FINAL DRIVE GEAR

FINAL DRIVEN GEAR
COUNTERSHAFT 4TH GEAR
ONE-WAY CLUTCH
Position, 4th speedProCarManuals.com

Electronic Control System

Electronic Control System

The electronic control system consists of the Transmission Control module (TCM), sensors, a linear solenoid and 4

solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under and conditions.

The TCM is located on the insulator center bulkhead, behind the driver's seat.

Shift control

Shifting is related to engine torque through the linear solenoid used to operate throttle valve B which is controlled by the

TCM.

Getting a signal from each sensor, the TCM detects the appropriate gear shifting and activates shift control solenoid

valves A and/or B.

The combination of driving signals to shift control solenoid valves A and B is shown in the table below.

Lock-up control

From sensor input signals, the TCM detects whether to turn the lock-up ON or OFF and activates lock-up control solenoid

valve A and/or B accordingly.

The combination of driving signals to lock-up control solenoid valves A and B is shown in the table below.

(cont'd)ProCarManuals.com

Description
Electronic Control System (cont'd)
TRANSMISSION CONTROL MODULE (TCM)

ENGINE
CONTROL
MODULE
(ECM) Shift Control

Lock-up

Control

TCS Control Unit
EPS Control Unit Engine RPM
Air Conditioning Signal Brake Switch Signal
Vehicle Speed Sensor Signal
Mainshaft Speed Sensor Signal
Countershaft Speed Sensor Signal

Self-Diagnosis
Function

Self-Diagnosis Indicator

INTERLOCK
CONTROL UNIT
Lock-up Control Solenoid
Valve B
Lock-up Control Solenoid
Valve A Shift Control Solenoid

Valve B

Shift Control Solenoid
Valve A

Linear Solenoid
Throttle Position
Sensor Signal
Engine Coolant

Temperature
Sensor Signal
Accet Pedal

Angle Signal

Service Check
Connector
ProCarManuals.com

Description

Hydraulic Control

The valve bodies include the main valve body, regulator valve body, lock-up valve body, secondary valve body, servo

body, throttle valve body and 2nd accumulator body.

The oil pump is driven by splines on the left end of the torque converter which is attached to the engine. Oil flows through

the regulator valve to maintain specified pressure through the main valve body to the manual valve, and the servo body,

directing pressure to each of the clutches.

Vehicle Speed Signal

2ND ACCUMULATOR BODY

REGULATOR VALVE BODY

LOCK-UP VALVE BODY

SERVO BODY

THROTTLE VALVE BODY

LINEAR SOLENOID
SECONDARY VALVE BODY
MAIN VALVE BODYProCarManuals.com

Throttle Valve Body

The throttle valve body is mounted on the servo valve body with the throttle valve built in.

LINEAR

SOLENOID
THROTTLE VALVE B

THROTTLE VALVE

BODY

Throttle Valve B, Linear Solenoid

Throttle valve B converts changes in the throttle opening to changes in transmission hydraulic pressure, to determine

transmission shift quality and lock-up operation. The throttle valve B also operates on accumulator back pressure to

make smooth changes from one gear to another.

The end of the valve contacts the linear solenoid which is controlled by the TCM.

The throttle pedal load has been reduced by eliminating the cable.

(cont'd)
LINEAR SOLENOIDProCarManuals.com