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Truck shudders between 45 and 55 MPH - 2004 Ford F150 FX4

I have a 2004 Ford F150 FX4 and I’ve been having a (hopefully) minor problem for the past 15k miles or so.

At normal city driving speed, 45-55 mph, Big Red (that’s her) tends to shudder a bit.

Picture yourself driving a 50 mph. Unless you are constantly watching your speedometer (instead of the road), your speed is probably going to drift up and down a bit.

No problems noticed when my speed drifts down, but when it begins to drift back up, the truck shudders a bit. Ta, da, da, da, etc.

If I apply the brakes for a second and then go back to the gas, it accelerates normally. If I just take my foot off the gas for a second and then apply the gas again it also accelerates normally.

Likewise, if I accelerate (slightly more pressure on the gas), it will accelerate right up through the shudder range with no problems.

It is only when my speed drifts back and forth during the 45 - 55 mph zone that the problem is noticeable.

If I am going up a hill, the shudder occurs at a lower speed, depending on how steep the grade is.

I did a tranny flush about 8k miles ago and it did not have any noticeable affect. The old ATF fluid looked almost new, likely because I have the towing package and the tranny has it’s own radiator. Also no towing, besides helping the occasional motorist get their cars out of ditches.

My rear seal recently had a leak (where the rear driveshaft sonnects ot the tranny), but I have replaced it and all is well there now, or seems so.

I’ve had people tell me that they think it sounds like a bad shifting solenoid. I’ve also had people tell me that a spark plug or two may be misfiring.

I keep thinking that if a solenoid was bad, wouldn’t it have problems ALL trhe time? I have no problems if I lay on the gas; just if I am trying to maintain a nearly constant speed.

And if it were the plugs, wouldn’t they misfire more often?

There is no diagnostic indicator, so no codes to be read.

Any suggestions?

My truck is due for spark plug replacement in around 9k miles (I’m at 91k right now), so i guess i can wait. I just want to see if anyone has suggestions now, in case this is something bad. Besides, I hear that the 2004 F150 Plug replacement is a horror show due to the plugs being notorious for breaking.

Other than the shudder, the truck runs perfectly.

The shudder might be caused from torque converter clutch shudder. The speeds you indicate is where the torque converter clutch should engage. You might want to try and add an additive to the tranny fluid that addresses torque converter clutch shudder such as this.


I agree with that a good additive may very well eliminate your problem but would suggest that you get the pan dropped, filter replaced and top off with the correct fluid and then add the snake oil. And I will also add, if the fluid had been regularly serviced it might never have developed the shudder and servicing it might eliminate possible future problems.

Already dropped the tranny pan and replaced the filter. The old ATF looked new too.

I’m worried about using Transmission Additives. I’ve heard alot of people say that it can make problems worse over the long run. Sometimes in the short run as well.

Is there any way to verify it is the TC and if so, is there a more permanent fix?

If you lock it in 3rd gear does the problem go away?

Hmmm. How do you lock it in 3rd gear?

I just drove home from work and decided to turn off overdrive. Surprisingly, there were no problems at all.

Not sure if that helps with diagnosis.

I’m afraid to drive it like that as a permanent fix.

I have personally added Trans-X, Trans-Medic and the Shudder stop mentioned above. The first 2 products are nearly identical and with some certainty I can say I have added them to hundreds of cars to correct your problem and other problems and as preventative maintenance when servicing the transmission and never seen any ill effects.

If you turned off overdrive you locked it in third. Sometimes “mechanic slang” is used here.

Ok, you’ve sold me. I’m going to pick up some Trans-X tonight. How many bottles do i need? Just 1 or do i need 2? Also, do I need to remove the same ammount of ATF or can I just dump it in and I’m done? Lastly, is it safe to leave in there or do i need to run it for a while and then flush the ATF again? Having just flushed the tranny earlier this year I don’t want to have to do it again unless i need to.

Thanks everyone for your advise.

I put in a bottle of Trans-X last night (after removing an equal ammount of ATF), and the shuddering is still there.

Do I need to add a second bottle or do you think it is something else I should try?

Drive with overdrive locked out unless you are driving at sustained speeds above 45. It might take 100 miles of highway driving with overdrive engaged to free up the clutch. It should not be necessary to add more Trans-X but another bottle won’t harm anything.

Trans-X won’t remedy clutch shudder. It’s not formulated for that, so I don’t know why anyone would recommend it.

You need the Instant Shudder Fixx for clutch shudder.


On the offchance that this problem is not caused by a transmission shudder do not rule out an ignition miss.

An ignition miss can be a funny thing that may only appear at certain times and when this is can be anybody’s guess. Logic dictates a miss should be noticeable all of the time and set a code but that’s not always true.

Seven years and going on a 100k miles is a long time to leave plugs in place and if there’s a problem with removing them then it’s because of the hokey interval of 100k miles or oblivion, whichever comes first.

Give you an example of this, and one which ate me up a bit before ironing it out. Customer has a car that started instantly hot or cold, idled like a new sewing machine, ran like a top no matter how hard the acceleration was, etc. The only issue was that the car would shudder pr even buck a bit ONLY at speeds around 40 MPH and ONLY when the accelerator was backed off of slightly and when an attempt was made to feather the pedal and maintain a steady speed.
This was traced back to a light film of corrosion on a coil wire. Cleaned that off and the problem went completely away.

Since this truck likely uses COPs maybe one, or more, of the plugs or coil end has corrosion on it. That would not be a rare thing. Just something for consideration if the transmission thing doesn’t work out.

We also have a 2004 FX4 and it started the same thing last summer. (It has 137K) It shudders around 45 mph but if I accelerate it goes away. Finally a light came on but the codes were nothing serious. I finally convinced the mechanic to replace the coils. He only replaced 3(they are around $100 each installed) and it has worked fine for the last year. But now it is doing it again. So I guess the others need to be replaced. Thanks for the tip about the 3rd gear and overdrive. I will check that out.


I’ve added both a bottle of “Trans-X” and a tube of “Dr. Tranny Shudder Fix” and the truck is still shuddering when the Overdrive is on when i try to maintain a constant speed of around 45-50 mph.

Adding those additives doesn’t seem to have made any change to the problem.

Any other ideas? In about 6 months I’ll be replacing the plugs and coils, so if that is the problem it should be fixed then. If it is something else i probably ought to plan for fixing it sooner.

I have a 2004 f150 Fx4 w/ around 130k. I have had the exact same issue for 2 weeks now. I also noticed it does not occur when overdrive is turned off.

This seems to be a common issue. This is the most common fix I’ve seen out there.

I pulled this off another forum:

I was having tranny shudder coming on around 45-50 mph range and sometimes at higher speeds when I would let off the gas a little. I could WOT thru it with no shuddering and would be fine with O/D off. Seemed to be related to lower RPM issue. I have 151K on truck and had plugs changed and tranny flushed around 105K. I ordered the COP’s from Ebay and installed this weekend and all my shuddering problems are gone. Looks like it was misfire problem with no codes showing up. Here is link to coils on Ebay, only $114.95 shipped for all 8.

I had the same exact problem with my 2006 f 150 4x4 with 130k + miles. It’s your ignition coils, they are dropping out under load. A very common concern when the tc locks up. You can pin point which one by having the dealer diagnose it with the IDS POWER BALANCE TOOL or you can get all new coil packs and be set for the future too. I personally would use motorcraft- or Accel- Either way changing all 8 is cheaper than the dealer and the problem will be solved for the cylinder that is currently dropping out and the one’s that will be dropping out in the future. It cost me a little under $300.00 on Amazon for 8 Motorcraft coils. It’s way better than the stealership.Trust me, anyone who has this same problem won’t regret swapping out all there coils.

@cdaquila-Carolyn, has ordinary Joe posted spam or just unauthorized advertising?

Am I missing something here @VOLVO_V70? I link to various parts sources often and never considered it unauthorized advertising.