40amp breaker running a 30 amp dryer
The answer to this question depends mainly on two factors. It really has no bearing on the dryer itself.


The size (diameter) of wire conductors from the breaker in the panel over to where the dryer plug is located. The primary function of the panel breaker is to protect the wiring from ever being used at a current rating over its rated size. If that wire is 10AWG then the breaker needs to be a 30A breaker. 8AWG wire may be used with a 40A breaker.
The dryer plug outlet itself will be rated for a particular current carrying capability. If that is a 30A outlet then it cannot be used with a 40A breaker even if the wire was rated at 40A.


If the dryer outlet looks like this it is a 30A outlet and the breaker will definately need changing. When doing so just make sure that the connecting cable has at least 10AWG conductors. (Note that wires with smaller AWG numbers are larger diameter wires capable of higher current).