Lexus RX300 (MCU15). Service manual - part 50

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CHASSIS — U140F AUTOMATIC TRANSAXLE

187CH01

187CH02

LHD Model

73

6. Snow Mode Control

General

The snow mode control enables the driver to select the snow mode which allows the vehicle to start in
2nd gear.

Operation

D When the snow mode is selected while the shift lever is in the “D” or “2” position, the vehicle can start

in the 2nd gear.  After a start, if the shift lever is in the “D” position, the transmission will shift up automat-
ically into 3rd and overdrive gears, as usual.  If the shift lever is in the “2” position, the transmission will
continue to operate in the 2nd gear.

D When vehicle is allowed to start in 2nd gear under the snow mode, it accelerates more gently and provides

better control.  This also minimize the fluctuation of the drive force transmitted to the tires realizing a
smoother start with minimum slippage.

" Shift Program A

⇒: Up-Shift

⇐: Down-Shift

Mode

Normal

Snow

Shift Lever Position

Normal

Snow

D (O/D Switch ON)

 1st 

⇐⇒ 2nd ⇐⇒ 3rd ⇐⇒

O/D

2nd

⇐⇒ 3rd ⇐⇒ O/D

2

1st

⇐⇒ 2nd ⇐ 3rd

2nd

⇐ 3rd

L

1st

⇐ 2nd

z

Snow Mode Switch Light

This switch is a momentary type switch which turns
on upon pressing and turns off upon pressing it
again.  Also, the snow mode is canceled once the
ignition switch is turned off and returns to the nor-
mal mode.

Snow Mode Indicaotor Light

A snow mode indicator light which turns on when
the snow mode is selected is provided in the com-
bination meter.

CHASSIS — U140F AUTOMATIC TRANSAXLE

74

JFAIL SAFE FUNCTION

This function minimizes the loss of operability when any abnormality occurs in each sensor or solenoid.
Control is effected as follows if a malfunction occurs in the sensors and solenoids:

D During a speed sensor malfunction, the vehicle speed is detected through the signals from the counter

gear speed sensor to effect normal control.

D During a counter gear speed sensor malfunction, 4th upshift is prohibited.

D During an ATF temperature sensor malfunction, 4th upshift is prohibited.

D During a malfunction in the solenoid valve SL1, SL2, or S4, the current to the faulty solenoid valve

is cut off and control is effected by operating the normal solenoid valves. Shift control is effected as
described in the table below, depending on the faulty solenoid.

When all solenoids are

When shift solenoid SL1 is abnormal

When SL2 is abnormal

When S4 is abnormal

When all solenoids are

normal

Traveling 3rd or 4th

Traveling 1st or 2nd

When SL2 is abnormal

When S4 is abnormal

Solenoid

Gear

Solenoid

Gear

Solenoid

Gear

Solenoid

Gear

Solenoid

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

ON

ON

OFF

1st

×

ON

#

OFF

OFF

3rd

×*

ON

OFF

2nd

ON

#

OFF

×

OFF

3rd

ON

ON

×

1st

OFF

ON

OFF

2nd

×

ON

#

OFF

OFF

3rd

×*

ON

OFF

2nd

OFF

×

OFF

3rd

OFF

ON

×

2nd

OFF

OFF

OFF

3rd

×

OFF

OFF

3rd

×*

OFF

#

ON

OFF

#

ON

3rd

OFF

×

OFF

3rd

OFF

OFF

×

3rd

OFF

OFF

ON

4th

×

OFF

ON

4th

×*

OFF

#

ON

ON

3rd

OFF

×

ON

4th

OFF

OFF

×

3rd

When SL1 and SL2 are

When SL1 and S4 are abnormal

When SL2 and S4 are

When SL1, SL2 and S4

When SL1 and SL2 are

abnormal

Traveling 3rd or 4th

Traveling 1st or 2nd

When SL2 and S4 are

abnormal

When SL1, SL2 and S4

are abnormal

Solenoid

Gear

Solenoid

Gear

Solenoid

Gear

Solenoid

Gear

Solenoid

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

SL1

SL2

S4

Gear

×

×

OFF

3rd

×

ON

#

OFF

×

3rd

×

ON

×

2nd

ON

#

OFF

×

×

3rd

×

×

×

3rd

×

×

OFF

3rd

×

ON

#

OFF

×

3rd

×

ON

×

2nd

OFF

×

×

3rd

×

×

×

3rd

×

×

OFF

3rd

×

OFF

×

3rd

×

OFF

#

ON

×

2nd

OFF

×

×

3rd

×

×

×

3rd

×

×

ON

4th

×

OFF

×

3rd

×

OFF

#

ON

×

2nd

OFF

×

×

3rd

×

×

×

3rd

*: B

1

 is constantly operating.

CH

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CHASSIS — U140F AUTOMATIC TRANSAXLE

75

JOVERDRIVE SWITCH

The overdrive switch has been adopted on the momentary type switch.
Pressing the momentary switch closes (turns ON) the contact points, and releasing the switch opens (turns
OFF) the contact points.  Accordingly, pressing the switch causes the signal to be input into the engine &
ECT ECU. 
Pressing the switch in overdrive turns OFF the overdrive. Pressing it again turns the overdrive back ON.
When the overdrive is OFF, turning the ignition switch from OFF to ON turns the overdrive back ON.

ODLP

ODMS

O/D OFF 
Indicator
Light

O/D Switch
(Momentry Type)

O/D OFF 
Indicator
Light

O/D
Switch

Ignition
Switch

ON

OFF

New

Engine &
ECT ECU OD2

O/D OFF 
Indicator
Light

O/D Switch
(Lock Type)

O/D OFF 
Indicator
Light

O/D
Switch
Condition

Ignition
Switch

ON

OFF

Conventional

Real
Switch
Condition

172GN01

172GN02

ON

OFF

ON

OFF

ON

OFF

ON

OFF

ON

OFF

Engine &
ECT ECU

CHASSIS — PROPELLER SHAFT AND REAR DIFFERENTIAL

187CH03

76

PROPELLER SHAFT

JDESCRIPTION

The LEXUS RX300 has adopted a 4-joint type propeller shaft.  A cross-groove type CVJ (Constant Velocity
Joint) with excellent high-speed and high-road durability is used for the No. 3 joint to reduce vibration
and noise.

No. 3 Joint (Cross-Groove Type CVJ)

No. 4 Joint
(Hooke’s Joint)

157CH29

No. 1 Joint
(Hooke’s Joint)

No. 2 Joint
(Hooke’s Joint)

Front

REAR DIFFERENTIAL

JDESCRIPTION

The convertional type, with a 2-pinion gear, is used.

" Specification A

Item

F17SU

Differential Gear Ratio

2.928

Drive Pinion

No. of Teeth

14

Ring Gear

Size

mm (in.)

170 (6.7)

Ring Gear

No. of Teeth

41

No. of Differential Pinion

2