CX31 and CX31 HT On-Highway Transmissions Caterpillar

A hydraulic retarder is available with the CX31 transmission. The retarder acts as a secondary braking system that is activated by electrical inputs from the transmission controller. The retarder will only be enabled in the following conditions: if the torque converter is locked up, fuel is not requested by the governor, fuel is not requested by the cruise control and fuel is not requested by the throttle. Control of the retarder is accomplished by a dash mounted set of switches. The retarder switches are preprogrammed in order to provide off, low, medium, or a high percentage of retarding.

1. The retarder will not engage during an ABS event. If an ABS event occurs while the retarder is active, the retarder will disengage.

2. The transmission retarder will not engage while a compression brake or an exhaust brake is operating. Should a compression brake or exhaust brake begin operation while the retarder is active, the retarder will disengage.

3. If the engine speed is turning faster than 2,600 rpm, the retarder will not engage. If the retarder is engaged and the engine speeds reach or exceed 2,600 rpm, the retarder will continue to function in order to help the operator reduce speed. The engine is protected against over speeding by the shift logic. However, there are conditions when the control logic is used to protect the hardware.

4. The retarder takes about one second before the transmission detects the performance of the retarder. Operators need to anticipate this delay in order to prevent the unnecessary use of the service brakes.

5. If the retarder has a switch that is not returned to the off position and the operator steps on the throttle, the accelerator pedal will disengage the retarder. The retarder will not engage again until the operator returns the switch to the OFF position and the operator engages the retarder again.

6. Do not use the retarder when the roads are slick. The use of the retarder on slick roads may cause a loss of vehicle control.

7. Low transmission fluid level will reduce retarder performance.

8. If the engine cooling system overheats during retarder operations, the engine cooling system pressure, coolant level, and engine rpm may be the source of the problem. Applications and ambient conditions may occur when a proper operating engine cooling system overheats while the retarder is applied. During such applications, the operator needs to decrease the percentage of retarding and the operator needs to apply the service brake.