I have a 2008 Ford Expedition with 5.4 liter motor. I makes has a vibration that happens when traveling from 35-55 miles per hour. It only does it when I have my foot on the gas and is worse when going up a hill. If I give it a lot of gas it will stop. I have brought it to multiple mechanics to no avail. I feels like you are driving across rumble strips off and on.
This is very likely a problem with the torque converter lockup mechanism, particularly if you haven’t changed the trans fluid every 30k miles.
A visit to an independent transmission shop should tell you for sure.
Just be sure that you don’t go to Lee Myles, Cottman, Mr. Transmission, or AAMCO if you want an honest diagnosis. Those chain-run scammers will tell you that you need a new/overhauled transmission, even if you only need to change the fluid and service the torque converter lockup mechanism.
Agreed with VDCdriver. It does sound like a torque converter issue. A transmission fluid change will often cure this problem. In some extreme cases a new converter may be needed but I would not panic over that just yet.
I’ve driven Fords for quite a while and have noticed that right around the 35 to 40k miles mark very subtle signs of this will show up on my cars. A filter and fluid change has never failed to cure it.
Ford has issued some bulletins over the years in regard to this problem but it exists even on models not covered by the bulletins.
Also agree with VDCdriver about avoiding the chain stores he mentioned. I could relate a few tales about some of them in regard to some major screwups.
To find out if it’s torque converter shudder, when the vibration occurs, keep steady pressure on the gas pedal, and with your left foot, slightly step on the brake pedal.
If the vibration stops, that’s torque converter clutch shudder.