2003 F150 Transmission issues.

fordmantpw · Oct 6, 2015

Mine never threw a code for the coil packs. The coil pack can report back correctly but not work properly. The only way to know for sure is to test each one individually.

N80 · Oct 6, 2015

That is weird. Most vehicles are exremely sensitive to misfires and coil pack issues and throw a code. In my experience with other (Japanese vehicles) the CEL will come on for coil issues even when you cannot feel or sense that there is any issue at all. Anyway, I will keep that in mind.

KubotainNH · Oct 6, 2015

N80 said:
I would think that cam sensors, EGR valve, speed sensors and coil packs would all throw a CEL code. Not sure about the speed sensor on the diff but I think it would probably throw a code too.

Not always, it depends on how bad it is. Sounds to me like you are in the early stages of something failing.

Scooby074 · Oct 6, 2015

Check the rear pinion bearing & driveshaft U joints.

Mine is similar vintage and has a rear diff thats on its way out. Similar feelings of vibration. Speed dependent, around 85-110 kph. A known issue on these trucks.

3930dave · Oct 7, 2015

Have the spark plugs been changed, esp. recently ?

A guy I know changed them on his 5.4 not long ago. A little later the trani seemed to be acting up. Turned out he hadn't torqued the last plug down - it was still threaded in, but definitely not seated/sealed. That problem some of the time threw a coil code for him, but it definitely felt like a trani problem.

Rgds, D.

deerefan · Oct 7, 2015

My 1997 F150 did this, mainly in o.d. around 50-55 mph. A trans flush with filter change solved it.

caver · Oct 8, 2015

I had a similar problem (05 F150 5.4 w/125K) when lugging the engine in overdrive. Sort of felt like the transmission was shifting. My mechanic said Ford recommends replacing the plugs at 100K and he had seen this problem before. He did that and problem went away for awhile. It came back a couple months later and like the others mentioned, it was a bad coil pack. I can think of only two times it was bad enough for the check engine light to come on.

On edit: Originally I talked to a respected transmission shop in SE Missouri and he was the first to say it was a plug problem. He advised against opening the transmission up or changing fluid.

N80 · Oct 8, 2015

This just can't be a coil pack. A misfire sufficient to cause the truck to shudder would just about have to throw a code unless the ECU is really primitive (and it does not seem to be since it has thrown plenty of other codes for various tiny issues).

Anyway, I've been driving all week with OD off and no issues. Switch it on and it starts up again. Almost has to be the transmission. Engine and diff issues should not be dependent on OD. I checked trans fluid and there is plenty (well above the 'do not add' line....maybe too much?). Fluid looks new. Also, this does not happen when lugging overdrive. It shifts just fine. This only occurs in neutral or light throttle situations at 45-55. Never starting off, never climbing a hill, never while accelerating.

I think I'm going to have a flush/fill/filter change and see if it helps.

fordmantpw · Oct 8, 2015

N80 said:
This only occurs in neutral or light throttle situations at 45-55. Never starting off, never climbing a hill, never while accelerating.

I think I'm going to have a flush/fill/filter change and see if it helps.

Occurring in neutral leads me to believe that it is not a tranny issue. Or do you mean neutral throttle?

That is exactly when my coil pack would act up. I would notice it mostly when coasting to stop lights or lightly cruising at 25-30 down the entrance road to work. Acceleration would rarely cause an issue. Mine never through a code.

Another thought, have you changed your fuel filter? That is a quick and easy place to start if you haven't.

tman1020 · Oct 8, 2015

Sounds exactly like our coil pack issue. However if it's time anyway a transmission flush does not sound like a bad idea. We did not throw a code right away but it did eventually.