I have a 120/240 dryer from Canada, and want to use it in a 240v country.
Very often, these types of dryers are also marketed in Pacific Rim markets where only 240V is available.  In this case, they build the dryer slightly differently, adding an internal 240V/120V transformer for the small number of 120V loads inside the machine (typically the motor). 

I would start by getting the schematic for the 240V version of this dryer. Then compare it to the 120V schematic, and see what needs to change.  

DO NOT - DO NOT - use a "step down" transformer without extreme care for how neutrals are bonded in the dryer and with your power supply.  If a step-down transformer isn't applied painstakingly correctly, it would end up energizing the chassis of your dryer at 230V.