i need to know how much your rpm is at 60mph 70mph 75 mph and 80mph

mine is 60mph 2600 rpm.......70mph 3000rpm..... 75mph 3100rpm and 80mph 3200rpm..... and it goes up from thier
is this normal??????
do these cars have an overdrive gear or just 4 gears?????
at 90 mph it looks like it just shifted to 4 gears....
could it be the timing belt????

help