Ford F-650 Owner's Manual page 122

Driving
Note: Manual transmissions should be downshifted to the lowest gear
possible, without exceeding the maximum RPM limit of the engine. This
maximizes the exhaust brake's retarding effect.
Note: Exhaust brakes operate effectively with automatic transmissions,
but performance varies with engine speed and the gear selected by the
transmission.
Note: Installing an exhaust or auxiliary brake does not necessarily
protect the engine from exceeding maximum governed speed. The
primary brakes should be used to make sure the engine never exceeds
maximum governed speed under any conditions.
WARNING: The exhaust brake is not recommended for use on
slippery or low traction road surfaces. Under these conditions a
loss of vehicle control could occur.
Exhaust brake operating characteristics
When you remove your feet from both the accelerator and clutch pedals
and the exhaust brake switch is in the on position, the exhaust brake is
activated. The following conditions should exist if the brake is operating
properly:
• A slight change in the sound of the engine when the exhaust brake is
activated.
• A smooth braking effect; do not expect a retarding effect similar to
sudden, hard application of the service brakes.
• The retarding force possibly felt acting against your body when the
brake is applied, depending on the grade and vehicle load. The brake's
retarding force is actually preventing the vehicle from going much
faster.
• Engine temperature remains in the normal operating range.
• During a descent, the tachometer usually shows a drop in engine RPM
depending on the grade and the vehicle load.
• Road speed usually decreases when the exhaust brake is applied
during a descent, except when the vehicle is carrying a heavy load or
the grade is extremely steep. In these instances, you may need to
apply the service brakes occasionally.
122
2012 F-650/750 (f67)
Supplement, 2nd Printing
USA (fus)