Got a '99 F150 4X4 5.4 Tri w/ 3" body lift. When it shifts out of first during moderate to heavy acceleration it seems to shift REAL hard. Not noticeable under light driving.

Does this sound like a tranny problem or short drive shaft problem?

What kind of checks can do? Thanks to all.

 

you need a programmer. get a gryphon with a custom tune. i can make mine go from squeeling tires when i shift from 1st and 2nd. OR i can make mine where i can't feel my truck shift at all. call bill over at powerhungry performance

 

Didn't I see in another thread where you just put very tall tires on, thus changing the effective gears? If so, your transmission is confused. The PCM is telling it to shift based on speed and the speedometer is way off. You need to get a tuner and recalibrate the speedometer as mentioned in the other thread. You will need to buy a tuner as they are specific to one truck at a time. You can't just borrow one. The only other option is to have the dealer recalibrate it and pay whatever they charge, $65 to $100.

 

I bought this truck bout a week ago and it already had the lift/tire combo. The guy I bought it from is a good friend and the lift and tires where already on as well. The truck has always shifted funny for the four years my friend has had it.

Wasn't sure if the hard shift was related to the speedo being off. I appreciate the feedback. I'll hook up a tuner a cal the speedo, hopefully that sets me straight.

 

Yup, I have to agree that the tire size is horking up the computer. It is expecting to see stuff that matches the parameters it's programmed for and is seeing something different and that's causing the issue. It's even possible that it's shifting off of the failed VSS table because of what it's seeing and that will really mess things up with larger tires.

Darrin

 

Well looking at some of the programmers that are heavely mentioned on here I think I'm going to attempt the dealer for the correction and see if that works.

Thanks to all for the information.

 

mine does that when it heats up. trans guy said the computers increasing line pressure do to wear. pulling it this week.

 

Well, I have a 2000 Ford Expedition with the 5.4L That does that same thing. The mechanic said when I called him that the tranny fluid level might be low/too high, or that the axle is sticking or start gear is worn. It would only do it if I accelerated faster than just a normal take off. I took it in and got my transmission flushed and cleaned and haven't had any problems since. Might give that a go.