so im driving down the freeway crusing at 70mph and i look at my guages. the tack is sitting at 3grand when im doing 70mph. it feels like the motor is struggling to keep up. its not losing power just feels like its working to hard to be going so slow. i can shift from D to 3rd at 70 and tack wont move at all. is my car not shifting past 3rd? would changing trans oil help? it hasnt been changed in a good 2 years that i know of.