Hello, I have a 2002 ford f150 lariat fx4 and the engine (5.4 triton) won't go past 3x rpm's no matter how hard I press. The tranny shifts at random times and mechanics had no clue and so I wanted to swap out the whole thing, I've got about 10,000. I was looking into getting the same engine supercharged but I need help picking the right transmission and axles, I'm looking into making it kind of a prerunner, I already got KYNG shocks and new leaf springs. With upgraded control arms and sway bars. Just need the power to get her going fast off road.

 

If your still interested in finding the problem, what has been done so an elimination can be done.
Transmission shifting is done from the computer under electric control.
Random shifting is not really possible unless the PCM is faulty or input data sensors are intermittent..
This needs to be explained in more detail.
Need to know;
How is starting, idle, any codes, has a Scanner been used to look at live data etc.
Has restricted exhaust been rules out?

Good luck.