Members of the RMT union had voted in favour of industrial action by four to one.
The row is over union demands for all Tube Lines staff to be allowed to join the Transport for London pension scheme and receive the same travel concessions as those who work for London Underground.
Maintenance staff on three tube lines are entering their third day of strikes today.
A strike affecting the Jubilee, Northern and Piccadilly lines goes ahead from 4pm.
Union bosses have forecast "widespread" disruption, as workers who maintain and upgrade tube lines go on strike next week.