Ford Expedition Vibration When Accelerating

2006 Ford Expedition. My Ford has 113K miles on it. The truck, when getting up to higher speeds runs and shifts perfect.  We changed the ignition coils and spark plugs, transmission fluid, oil changed, and got the catalytic converter checked and it test fine. The U-joints are good to.  The problems are that the idle is fine, but when coming off from a stop accelerating to around 30 mph the RPM’s go up and down.  Then the truck starts to vibrate. It is almost as if you are riding on the side of the highway on those ridges that are on the road to keep truck drivers awake. But after you let off the gas it goes away and i can then drive it normal untill i get the speeds down slower again, but does it when accelerating.

When you mash on the gas everything is fine. The transmission shifts perfect. Just when going at a slow speed. It makes a loud humming sound and vibration. Could have sworn this was a U-joint connected to driveshaft. But we went to the repair shop, the mechanics said they are all fine. I feel like if i get on the gas pedal and go fast enough from the  get-go it doesn’t happen at all, and i can drive it and manipulate it to not vibrate at all. Sometimes that works.

I really need to figure out the problem. Do you think it could be the torque converter or something wrong with the trans.? Thank you.

Answer: Shaking and vibrating when accelerating as you describe is usually caused by an ignition problem. If the coils and plugs did not help, have the plyg wires inspected. Spraying water on them and then doing a brake torque may get them to break down and start to misfire. This brake torque- accelerating with foot firmly on brake in drive gear- is also a good way to rule out a drive train component such as a transmission, u-joint or rear end problem. If it does not act up like this, then you may have a rear end issue.

My first question would be is the check engine light on? IF so go to auto zone and have them read the codes for free. I am not sure how brake torquing it is going to help you but if you indeed have a u joint going bad it might put it over the top to broken and I suppose that would help id the problem.

could you perhaps take a video with your digital camera of when this is happening and send it to me? it would help a lot in getting you a proper diagnosis.

If this shaking and vibrating happens when slowing down then it would not be an ignition problem like a bad spark plug or plug wire. It really does sound like a bad U joint. Especially if you can sort of play with the gas pedal to get it to stop even when accelerating. Putting any sort of a load on the driveshaft by using the gas pedal will cause a U joint to stop vibrating. Try slowing down until the vibration starts and then quickly pop into neutral. If it stops that would really sound like a bad U joint. It could possibly be in the transmission but that would be much harder to diagnose. Let us know what you found with the problem on your Ford truck.

I just bought a 2006 f150 extended cab w/ 5.4 V-8 and it vibrates when accelerating from a stopped position but not all the time—happens more when the wheel is turned. It definitely feels like the vibration is coming from the left front side. I just got it back from the shop and the mechanic told me the vibration was stemming from the rear and that he exchanged the fluid but that he expects the problem to continue. Any ideas?

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