Dodge 2007 Ram Pickup 3500 - Manual (Page 324)

The “SERVICE 4WD” warning light monitors the electric
shift 4WD system. If this light remains on after engine
start up or illuminates during driving, it means that the
4WD system is not functioning properly and that service
is required.
WARNING!
Always engage the parking brake when powering
down the vehicle if the
؆Service 4WD؆ light is
illuminated. Not engaging the parking brake may
allow the vehicle to roll which may cause personal
injury.
NOTE: Do not attempt to make a shift while only the
front or rear wheels are spinning. This could cause
damage to driveline components.
When operating your vehicle in 4WD LO, the engine
speed is approximately three times that of the 2WD, 4WD
AUTO or 4WD HI positions at a given road speed. Take
care not to overspeed the engine and do not exceed 25
mph (40 km/h).
Proper operation of 4 wheel drive vehicles depends on
tires of equal size, type and circumference on each wheel.
Any difference in tire size can cause damage to the
transfer case.
Because 4 wheel drive provides improved traction, there
is a tendency to exceed safe turning and stopping speeds.
Do not go faster than road conditions permit.
324 STARTING AND OPERATING