During lets just say normal driving the trans shifts at 10-15 mph for 1-2, 25-35 mph for 2-3 and goes into 4th gear (overdrive) around 42-50 mph depending on throttle %.
Its pretty normal to see the car lag when trying to go up a hill in 4th gear because its a highload gear, so most of the time the car will downshift or you'll have to press your foot down to make it drop into 3rd and make it up that hill.
If you drive around in the city alot and most of your speeds are at or below 45-50 mph just keep the trans in 3 all the time, it'll stop that 4th gear lag around town and hilly metro areas.
