Don't forget to buy food and drinks in advance if you need them: train stations do not always have shops, while onboard cafés are not always available and often very expensive.
When the journey is as long as between Tucumán and Buenos Aires, you should consider to take a flight to Buenos Aires. If you book in advance, low cost airlines can provide flight that will make you save not only time but also money.
Which stations serve the rail line Tucumán - Buenos Aires?
You can take the train to Buenos Aires at Tucuman (Tucuman - Argentina), which arrives at Buenos Aires (Retiro Cap.fed - Argentina).
How long will it take you from Tucumán to Buenos Aires by train and when do the trains leave?
The average duration of the journey is 16 hours and 36 minutes, but the fastest connections take you to Buenos Aires in 14 hours and 40 minutes. The first train leaves from Tucumán at 01:12, while the last one leaves at 23:12.