It could be one of the CV axles is out of balance. Does the vibration occur on one side more than the other? All front wheel drive cars have CV (constant velocity) axles. The CV axles connects each front wheel to the transmission on front drive cars. If one of these axles is off balance, it will have a similar effect as a wheel being off balance.

FYI - you need to take apart the suspension in order to remove the CV axle. If the axle is the issue, it might cost a little more than you expected ($150 - 300).

cv joint maybe or the torque converter in the transmission ! try using regular drive instead of overdrive and see if that helps !

maybe rotate your tires my car does the same thing i just deal with it because its old or maybe 1 tire is defective..

a broke cord in tire will do that

I drive a 2002 Buick Lesabre. When the speed is between about 45 and 55 mph the car shakes or vibrates. Once it get over 55 it stops. Someone told me it was probably a tire out of balance, so I had the tires balanced, but it is still doing it.

It seems to be a bit worse when going uphill.

It also doesn't do it when decelerating and when I let my foot off the gas pedal.

Any ideas or suggestions.