I believe the $5 day was a 10 hour day.
While Ford made quite a splash with his headlines - and the commentary "I have to pay my employees enough wage to be able to buy my own cars," the wage scale was self-serving.
In actuality, by the time of the Model A, Charles Sorensen, among others, had instituted more normal pay scales, and working conditions for the time. While not brutal, except for occasional skirmishes with Employee Unionization efforts, Ford was noted for "getting his pound of flesh" and in the tone of the times (Great Depression) employees were easily replaced.
Using the inflation calculator
http://www.in2013dollars.com/us/inflation/1929?amount=5 $5 in 1914 would be $128.29 today, or about $12.80 an hour.
My last numbers for actual wage scales for automobile assembly is about $22 per hour for a 40 hour week, or about $44K per year. Full benefits, including a Union sponsored retirement.
Joe K