2003 Taurus shaking at 55 MPH

My 2003 shakes/jerks back and forth at 55 mph. Took to a mechanic, they found nothing…car did not jerk. Check engine light on (although it has been on for years)…checked transmission codes and found nothing…could be oxygen sensor? any ideas

Here’s an idea: fix whatever is required to make the CEL go off. And if the transmission fluid has never been replaced, replace it.

Well since you are already driving a death trap, I suggest you pay up your life insurance first. You obviously have not fixed any engine issues that might lead to engine shaking. That is what the CEL light is for. Go to a Advance auto or other chain shop, have them pull the engine codes for free. Post the results here with the milage and we will find out whether the betting pool that you will die needs to change. Really, are you seriously saying you drive this car like this without fixing it?

This could well be a problem with the suspension.  I suggest taking it to a real suspension shop (not a garage that can replace shocks and do a basic alignment or even a good tyre store, but a shop with the real equipment and knowledge of automotive suspension work.