ALLISON-OM1334EN

USING THE ENGINE FOR DOWNHILL BRAKING TO SLOW

THE VEHICLE OR EQUIPMENT

To use the engine as a braking force, select the next lower range. If the vehicle is

exceeding the maximum speed for the lower range, use the service brakes and/or

hydraulic retarder to slow the vehicle so that the lower range is obtained.

USING THE HYDRAULIC RETARDER

WARNING:

The transmission incorporates a hold feature to pro-

hibit upshifting above the range selected during normal driving. For

downhill operation, select a lower transmission range. However, if

engine governed speed is exceeded in the held range, the transmis-

sion may upshift to the next higher range and damaging engine

overspeed is a possibility. Use the vehicle brakes or retarder to pre-

vent exceeding engine governed speed in the held range.

NOTE:

Transmissions that do not have a lockup clutch (AT 540,

AT 542, AT 545) provide less engine braking than units which have a

lockup clutch. Downhill speed control for non-lockup units without a

retarder must rely on the service brakes.

WARNING:

Do not use the retarder during inclement weather or

when road surfaces are slippery. De-energize the retarder at the

master control switch.

CAUTION:

Observe the following cautions when driving a vehicle

equipped with an input or output retarder:

• APPLY AND OPERATE THE RETARDER WITH ENGINE AT

CLOSED THROTTLE ONLY.

• OBSERVE TRANSMISSION AND ENGINE TEMPERATURE

LIMITS AT ALL TIMES. Select the lowest possible

transmission range to increase the cooling system capacity and

total retardation available.

• OBSERVE THE RETARDER “ALERT LIGHT” to ensure that

the vehicle control system is functioning properly.

• DO NOT OPERATE THE INPUT OR OUTPUT RETARDER

SIMULTANEOUSLY WITH AN ENGINE EXHAUST BRAKE.

Extreme torque loads can be produced in the range section,

damaging the transmission.

• In the event of OVERHEATING, DECREASE USE OF THE

HYDRAULIC RETARDER; USE THE SERVICE BRAKES.

ALLISON AT, MT, HT SERIES ON-HIGHWAY TRANSMISSIONS

OPERATOR'S MANUAL

2000