This is true.
I put 3.42's in my rear with a th400 tranny and it turns, as least it should, at 3500 RPMs at 80 miles per hour. I'd have to get up over 120 to redline, and that hasn't happened and probably never will since that's a little too high in the 1/4 mile
Anyway, play with this website
http://www.race-cars.net/calculators/et_calculator.html