Automatic gearbox and diff ratio question

[TI5650]

Nice simple one today just wondering if when I change from a 3.07 to a 345 ratio diff if the 5 speed auto in my 328i will take advantage of the 5 th gear for lower rpm crusing at normal road speed (60 kmh) I guess this is a question relating to how the automatic chooses what gear to drive in. Usually 4th for normal driving, 5 th at like 75+ is how it acts for me. Anyone who has experience that can chime in is appriciated

[atlantisvip]

Not at all a pro at these things but I know you will definitely pull harder and your top speed will go down cause you will rev much higher at high speeds. I have an auto with a 3.91.. So ask me how I know