I just had a new engine put in my 97 5.4L with a new transmission. It is still underwarranty but I don't trust the shop that did the work since I have had to repair many parts/items they broke or didn't repair correctly.

Anyway, I have a drivetrain shake or heavy vibration from the engine or transmission. It happens around 35 mph or above at least it is most noticeable there. If I let off of the gas and then lightly get back on it , it will start to shake or vibrate the entrie center of the car. It almost feels like it is surging and shaking.

This isn't wheel shake. I am quite sure it isn't driveshaft shake either. This is something in the engine or transmission.

I am getting no SES codes, etc. I can replicate it very easily. Does anyone have an idea of what it could be. Thanks.

 

start with the simplest first.

take the driveshaft and rotate it 180 degrees. if this doesnt work then check if some weights were knocked off of it (should be different colored oval shaped spots near the front and back if a weight is gone).