ACURA NSX 1997 Service Repair Manual

2nd Gear in Positions

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

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

2. Power is also transmitted to the secondary shaft 2nd gear because hydraulic pressure is applied to the 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.

NOTE: Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 2nd gear exceeds 1st gear

speed, power from 1st gear is cut off at the one-way clutch.ProCarManuals.com

Description

Power Flow (cont'd)

3rd Gear in Positions

1. Hydraulic pressure is applied to the 3rd clutch. Power from the mainshaft 3rd is transmitted to the countershaft 3rd gear.

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

NOTE: Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of the 3rd gear exceeds 1st gear

speed, power from 1st gear is cut off at the one-way clutch.ProCarManuals.com

4th Gear in Positions

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

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: Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 4th gear exceeds 1st gear

speed, power from 1st gear is cut off at the one-way clutch.ProCarManuals.com

Description

Electronic Control System

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

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

located on the insulator center bulkhead, behind the driver's seat.ProCarManuals.com

Shift Control

Engine torque controls shifting through the linear solenoid. The linear solenoid is controlled by the TCM, and it is used to

operate the throttle valve.

The TCM instantly determines which gear to select by various signals sent from sensors, and actuates shift control

solenoid valves A and B to control shifting. Also, Sport Shifting mode has been adopted to shift gears up and down manu-

ally in position, while using the shift switch on the steering column's right pod.

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

Sport Shifting (Manual Shifting) mode

In position, the driver can use the shift switch on the steering column's right pod to shift gears up and down, much

like a manual transmission.

• Pushing up on the shift switch: Transmission upshifts to the next higher gear.

• Pushing down on the shift switch: Transmission downshifts.

The number of the selected gear is displayed in the shift indicator next to the indicator.ProCarManuals.com

Electronic Control System (cont'd)
Description

• Automatic shifting control in Sport Shifting mode

This position also has automatic shifting areas:

• 1-2 upshift

• 4-3 downshift, 3-1 downshift, 2-1 downshift

depending on vehicle speed. To prevent engine over-revving, the transmission has a 1-2 automatic upshift speed, and 4-3,

3-1, 2-1 downshift allowable speeds.

• When the vehicle reaches the 1-2 automatic upshift speed, the TCM outputs the 1-2 upshift signal to the transmis-

sion and the transmission upshifts to 2nd from 1st gear.

• When the vehicle is coasting over the 4-3 downshift allowable speed and 3-2 downshift allowable speed, the TCM

does not input the downshift signal from the shift switch, and the transmission does not downshift.

• When the vehicle is coasting over the 2-1 downshift allowable speed in 2nd gear, the TCM inputs the signal to wait

until it reaches the 2-1 downshift allowable speed, then the shift indicator blinks to indicate it is waiting to downshift

to
1st.

When the vehicle decelerates to a stop, the transmission shifts to 1st gear automatically.

The transmission can be shifted to 2nd gear by pushing the shift switch up while the vehicle is stopped. This allows the

vehicle to start off in 2nd gear.

Lock-up Control

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

solenoid valve A and/or B accordingly.

The lock-up control mechanism comes into operation in 2nd, 3rd, and 4th, in positions.

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

Hydraulic Control
Description

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

body, the servo body, the throttle valve body and the 2nd accumulator body.

The ATF pump is driven by splines on the left end of the torque converter which is attached to the engine. Fluid flows

through the regulator valve to maintain specified pressure through the main valve body to the manual valve directing

pressure to each of the clutches.

The shift control solenoid valve assembly, the lock-up control solenoid valve assembly and the linear solenoid are bolted

on the outside of the transmission.ProCarManuals.com

Throttle Valve Body

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

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.ProCarManuals.com

Hydraulic Control (cont'd)
Description

Regulator Valve Body

The regulator valve body is mounted on the main valve body with the regulator valve, the lock-up control valve and the

cooler relief valve built in. The stator shaft arm contacts the regulator valve spring cap.

The hydraulic pressure (line pressure) is controlled by the regulator valve.ProCarManuals.com

Regulator Valve

The regulator valve maintains a constant hydraulic pressure from the ATF pump to the hydraulic control system, while

also furnishing fluid to the lubricating system and the torque converter.

Fluid from the ATF pump flows through B and B'. The regulator valve has a valve orifice. The fluid entering from B flows

through the orifice to the A cavity. This pressure of the A cavity pushes the regulator valve to the right side, and this

movement of the regulator valve uncovers the fluid port to the torque converter and the relief valve. The fluid flows out to

the torque converter. The relief valve and regulator valve move to the left side.

According to the level of the hydraulic pressure through B, the position of the regulator valve changes, and the amount of

fluid from B' through D and C also changes. This operation is continued, maintaining line pressure.

Stator Reaction Hydraulic Pressure Control

Hydraulic pressure increases according to torque are performed by the regulator valve using stator torque reaction. The

stator shaft is splined with the stator in the torque converter, and its arm end contacts the regulator spring cap. When the

vehicle is accelerating or climbing (Torque Converter Range), stator torque reaction acts on the stator shaft, and the stator

arm pushes the regulator spring cap in the direction in proportion to the reaction. The stator reaction spring compresses,

and the regulator valve moves to increase the line pressure which is regulated by the regulator valve. Line pressure reaches

its maximum when stator torque reaction reaches its maximum.ProCarManuals.com