i have an 01 5.4 expedition auto trans., as i am driving my truck seems like it slips into neutral, rpms go up but the truck slows down. if i down shift into lower gear im able to go again, then i'll go back into overdrive and it seems fine for a bit shifting through the gears, then a few moments later it seems like im back into neutral. can anyone please help me with diagnoses. will i need a new tranny or is it some internal parts i can change out..

 

Not to state the obvious, but did you check the fluid level in Park with the tranny warmed up?

 

yes, the fluid levels were good and i even put lucas stop slip transmission in to see if that would help but it didn't...