Lexus RX300 (MCU15). Service manual — part 50
CH
BO
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
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