Retarding system

1. A vehicle, comprising:

an engine;

a transmission associated with the engine;

an engine retarder having a deactivated state and an activated state, the engine retarder configured to reduce a speed of the engine in the activated state; and

a fan associated with the engine, the fan configured to be activated in response to a selection of a transmission gear ratio less than or equal to a threshold gear ratio while the engine retarder is in the activated state, wherein the fan assists in further reducing the speed of the engine while activated.

2. The vehicle of claim 1 , wherein the fan is configured to be deactivated while the engine retarder is in the activated state if no transmission gear ratio has been selected.

3. The vehicle of claim 1 , wherein the engine retarder is configured to increase a natural resistance of the engine in the activated state.

4. The vehicle of claim 1 , further comprising a controller configured to transition the engine retarder from the deactivated state to the activated state in response to a determination that deceleration of the vehicle is desired.

5. The vehicle of claim 4 , wherein the controller is configured to sequentially activate the fan if the engine retarder is activated and if the selected gear ratio is greater than or equal to the threshold gear ratio.

6. The vehicle of claim 4 , further comprising a throttle pedal configured to increase the speed of the engine, wherein the determination is based on a release of the throttle pedal from a depressed position.

7. The vehicle of claim 4 , further including an operator interface device configured to enable the engine retarder, wherein the determination is based on the operator interface device being in an enabled position.

8. The vehicle of claim 1 , further including a hydraulic pump driven by the engine and a motor fluidly connected to the hydraulic pump, wherein the fan is driven by the motor.

9. The vehicle of claim 1 , wherein the engine retarder comprises one of an exhaust brake and an engine brake.

10. A method of braking a vehicle, comprising:

activating an engine retarder connected to an engine of the vehicle, wherein activation of the engine retarder provides a retarding torque to the engine; and

activating a fan associated with the engine, while the engine retarder is activated, in response to a selection of a transmission gear ratio greater than or equal to a threshold gear ratio, wherein activation of the fan provides additional retarding torque to the engine.

11. The method of claim 10 , further comprising deactivating the engine retarder, and deactivating the fan in response to deactivating the engine retarder.

12. The method of claim 10 , further comprising deactivating the fan and keeping the engine retarder activated in response to deselection of the transmission gear ratio.

13. The method of claim 10 , further including determining that deceleration of the vehicle is desired and activating the engine retarder in response to the determination.

14. The method of claim 10 , further including traversing a declining grade with the vehicle while the transmission gear ratio is selected.

15. The method of claim 10 , further including sensing a position of a throttle pedal of the vehicle, wherein the engine retarder is activated in response to the sensing.

16. A method of braking a vehicle, comprising:

receiving a first signal, the first signal indicative of a desired deceleration of the vehicle;

receiving a second signal, the second signal indicative of an enablement of an engine retarder connected to an engine of the vehicle;

activating the engine retarder in response to receiving the first and second signals, wherein activation of the engine retarder provides a retarding torque to the engine;

receiving a third signal, the third signal indicative of a selection of a gear ratio of a transmission associated with the engine, wherein the selected gear ratio is greater than or equal to a threshold gear ratio; and

activating a fan associated with the engine, while the engine retarder is activated, in response to receiving the third signal to provide additional retarding torque to the engine.

17. The method of claim 16 , wherein the first signal is indicative of a release of a throttle pedal of the vehicle from a depressed position.

18. The method of claim 16 , further comprising deactivating the engine retarder, and deactivating the fan in response to deactivating the engine retarder.

19. The method of claim 16 , further comprising receiving a fourth signal indicative of deselection of the selected gear ratio, and deactivating the fan, while the engine retarder is activated, in response to receiving the fourth signal.

20. The method of claim 16 , wherein the selected gear ratio comprises a minimum desired gear ratio selected by an operator of the vehicle.