If the travel speed and engine speed continue to rise, the brake is automatically applied to prevent the engine
speed from rising too far.
Neutral coast prevention function
If the gear shift lever is set to NEUTRAL position (N) while driving a machine at travel speed of above 4 km/h,
the gear shift cannot be changed to neutral. The centralized warning lamp flashes and the alarm buzzer sounds
intermittently.
If a travel speed exceeds 4 km/h while going downhill with the gear shift lever in NEUTRAL position (N), the
centralized warning lamp flashes and the alarm buzzer sounds intermittently.
When the travel speed exceeds 23 km/h, the gear speed is automatically shifted to the gear speed optimum to
the current travel speed.
When traveling, and particularly when traveling downhill, never set the gear shift lever to NEUTRAL position (N).
Always set the gear shift lever in D to 1 position while traveling.
METHOD FOR TRAVELING DOWNHILL
When traveling downhill, travel at a safe speed which matches the width of the road, the condition of the road
surface, and other conditions of the jobsite.
WARNING
• When the machine stops, chock the tires immediately.
• For the maximum permissible speed when traveling downhill using the retarder brake, see the
brake performance curve for the downhill distance and grade.
Traveling continuously downhill at a speed greater than the maximum permitted speed on the brake
performance curve is dangerous as the retarder brake may be damaged.
• If the retarder oil temperature caution lamp on the machine monitor lights up when the retarder is
being used, shift down to travel downhill.
(In this case, the centralized warning lamp lights up and alarm buzzer sounds.)
It the retarder oil temperature caution lamp does not go out even when the transmission is shifted
down, stop the machine immediately, set the gear shift lever to NEUTRAL position (N), run the en-
gine at 1800 rpm and wait the retarder oil temperature caution lamp goes out.
• If the retarder brake loses its effect when it is used for traveling downhill, do as follows.
1.
Return the retarder control lever to its original position once completely, then operate the re-
tarder control lever again.
2.
If the retarder still has not effect even when the retarder control lever is operated again, return
the retarder control lever completely to the “RELEASE” position, then depress the brake pedal
to stop the machine, then contact your Komatsu distributor for repair.
• Operate the retarder control lever gradually.
Sudden braking might cause an accident due to tire slip.
• When traveling, and particularly when traveling downhill, do not set the gear shift lever to NEUTRAL
position (N).
If the gear shift lever is set to NEUTRAL position while driving the machine at 4 km/h or traveling
downhill, the gear range is not changed to NEUTRAL. The centralized warning lamp flashes and the
alarm buzzer sounds. Always set the gear shift lever in D to 1 position while traveling.
NOTICE
• If the retarder control lever is operated when traveling downhill, the transmission can be shifted
down sooner than with normal deceleration.
It is also possible to travel without shifting up.
• Do not accelerate or shift up when using the retarder.
The engine speed rises and the alarm buzzer may sound and the engine overrun caution lamp and
centralized warning lamp may light up.
MACHINE OPERATIONS AND CONTROLS OPERATION
3-190
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