3000 at 70 mph is too much. To see if you're getting into overdrive just shift down to third gear when cruising at 60 mph. If the rpm's jump high you were in overdrive. Shift back to drive and the rpm's should drop back to where they were. If you shift to third gear and nothing at all happens then you were in third gear already and you're not getting up into overdrive and something is wrong.

Mark