Ohare Clearing Customs from VIE Sat May 24 @ 1:30pm for 3:10pm flight
 

Is 1 hour 40 min long enough to do all that we will have to do ?

I wouldn't chance it.

deplane
passport control
retrieve bags
customs
drop off bags
take train to your domestic terminal
re-clear security
head to gate

I'd book that flight.

It totally depends on how many international flights are arriving at the same time! I can usually clear and be out the door on my way to another flight (or to my car to drive home) in 45 minutes, and I am among first ones off the plane because of riding closer to the front of the plane, in biz, first, or economy plus.

This is a tough one. As simpson says sometimes it's possible to breeze through all the steps in 45 minutes and having an hour and 40 minutes is tons of time. But what if your flight into O'Hare is delayed by 20 or 30 minutes, or what if the passport control line is an hour long (which is possible)? If you are risk averse or if huge airports give you anxiety you might not want to book the 3:10 flight and take the next one.

I flew VIE to ORD last week and arrived around 2:00. It took about 45-mins from the time I left the plane until I exited the arrivals hall with my luggage. I know there are lots of factors and actual mileage may vary, but it sounds like a big gamble.

Of course, when you drop your luggage as you exit the arrivals area of T5, the agents can make adjustments to your itinerary if needed, but if flight after the 3:10 is already fully-booked, you could end-up cooling your heels for several hours.

Depends on your seat. It would suck if you were in the back and it took you 15 min to get off the plane.

It also depends on if you land on-time.

I think getting through security quickly is your primary concern. We fly United but avoid ORD on return from international destinations because of this. Jeff_CR's points are spot on.

If you book that then it would be a good idea to sign up for Global Entry to speed you through I&C.

We arrived ORD at about 4:10 yesterday afternoon, and were on our way home at 5:00! Our plane was the first of several int'l flights to unload. We were very lucky! No lines to speak of.

Are you a US citizen or not?