your right 3t40 is your unit its also known as the TH125C. there is a throttle valve in the valvebody that works obviously with your throttle. the more gas you give it the further it pushesd the throttle plunger in. i work in a transmission shop. not only do i build them but im always rebuilding the valve bodies. if that valve sticks then its not going to let u up shift. that valvebody also has the pump built into it, as one unit. easy ways to check your trans is obviously look at the fluid make sure its red. it wont be bright red, it will be darker cause of the clutch material, as long as there is no metal ur good. also you can manualy put it into each gear at a stand still. if it ingauges and coasts in whatever direction u have it in then your clutches should be good. manual first, manual second, reverse, drive, etc