My tranny is slipping when it is in overdrive at 55mph or above. I have a 2000 5.4L with 90,000 miles. I have not replaced my tranny fluid. Could this be the cause? Is there anything else that could be causing this?

Thanks in advance!

 

Mine did the same thing. FInally found out the main seal was leaking but by then my tranny was messed up and i had to replace it. i would definetely try the fluid and check for any leaks before i did anything major