Hi I have a 3ltr v6 petrol automatic maverick  - I seem to have a problem with the automatic gearbox or something along those lines ?? looking for help or ideas on poss causes - when driving its revving far higher than it should and seems to be changing gear very late, struggling to get up hills and also an occasional whistle/ hissing (maybe unrelated) and overall loss of "umpth"  !

hope someone has some ideas??

In my experience of this model the auto transmission can be a weakness. The place to start is change the fluid. Use a suction device to drain through the dipstick hole. Measure amount withdrawn. It won’t Be anything like the full capacity. I used Amsoil ATF, don’t spend time finding the right Mercon grade. Drain and refil several times after driving a short distance to mix it up each time. You’ll need about 5 litres each refill