99′ F150 Transmission Shutter 45-55 mph

  • Avatar of lots-of-luck lots-of-luck 
    Posts: 592

    Anyone experience this with there own F150? I just had it happen a little while ago while driving home from St. Cloud and I have just started my research online. Seems like this happens occasionally from my initial reading, but I have yet to fully research the probable diagnosis and method of correction. Initial comments talk about worn out transmission fluid corrected by a flush and fluid replacement.

    As soon as the transmission shifts into OD at 45 m.p.h. it starts to shutter until 55 m.p.h. Accelerating past 55 m.p.h. the shutter subsides. Only happens during acceleration and does not happen during deceleration. Obviously requires a load. Babied it home.

    99′ 5.4 +/- 135k miles automatic transmission obviously

    Anyone experience this before?

    avatar trumar 
    Posts: 5,283

    Turn off your Overdrive and see if it still does it, if NOT your overdrive is going out ,IF it still does your trans may be going out .

    As a mechanic I am not a fan of trans flushes as it losens up all the fines built up in the convertor ,drop your pan and change filter and fluid . When doing this keep and eye on how much build up is the pan or on the magnet if you have one inside the pan.
    Fines are ok but no metal pieces big or small are good.

    Any question just holler back.


    Avatar of wade wade 
    Posts: 1,731

    I had a 95 F150 that did the same thing and I ended up putting in a new tranny…they shutter that you describe isn’t as noticelable after 55mph but it is still in the componets….

    Avatar of lots-of-luck lots-of-luck 
    Posts: 592

    I kicked OD off and the symptom went away. I believe it is limited to just the OD.

    avatar trumar 
    Posts: 5,283


    I kicked OD off and the symptom went away. I believe it is limited to just the OD.

    Try changing the fluid as it is fairly cheap to do or have down compared to the cost of a trans replacement and see what it does.

    avatar gregory 
    Posts: 517

    i have had this problem in my 95 f250 and and a explorer i would highly recommend just changeing the tranny fluid and adding lubeguard and a packet of lubeguard dr tranny instant shudder fix.. it worked for me bumber to bumber sells it..

    avatar riveratt 
    Posts: 1,464

    Tell you what. Ignore the transmission. They don’t shudder for 10mph then go away. Instead check and find out what cylinder is misfiring. I’d bet that is the root cause.

    The info you found online is referring to the old torque converter shudder. It would occur just as the transmission shifted into O/D and felt exactly like you drove over a rumble strip by a stop sign. But that specific concern didn’t carry over into the 97 and newer F series as the trans was redesigned. But like I said that shudder didn’t last but a brief moment. If you actually have a slip bad enough to cause a shudder your fluid will be black and stink plus your over drive light will be flashing.

    My money is on a cylinder misfire most likely from a failed coil pack. If I was a betting man I’d say it is the #4 cylinder. Check for signs of coolant seepage (if not wet then white residue on top of coil) on the coil positioned on the rear of the passenger side of the engine. There is a heater hose clamp above it that likes to lose tension and dribble coolant onto the coil causing it to fail. Of course it could as easily be any of the other 7 too.

    Good luck!

    Oh forgot to add. The reason the sympton goes away with the O/D off is the RPMs are higher and the ignition system isn’t working as hard. The same will happen by manually moving the gear selector into 2.

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