Ford Fairmont Shudder

I have a 2005 Ford Fairmont that has only done 71000kms. When travelling on expressways it some times develops a severe shudder to the extent that I have to pull over. Generally when I pull over and wait for a minute or two (engine still idling) and then pull out it goes away. I also have noticed a loud thump from underneath the vehicle (usually whilst reversing) and am not sure if this has something to do with the shudder. My mechanic says he can’t find any probelms. Does anyone have any suggestions as to what might be causing this problem?

I am assuming that you live in Australia, where the Ford Fairmont is a variant of the Australian-made Ford Falcon. (The Fairmont name disappeared from the US market a few decades ago!)

Anyway…we need some clarification regarding your car’s problems.
Does the shudder take place continually at high speed, or does it take place briefly and intermittently?

If it is a brief and intermittent shudder, then I would suspect a problem with the torque converter lock-up clutch–assuming that the car has an automatic transmission. (You didn’t specify the type of transmission!)

If the shudder is continual once you reach a certain speed, then it would be more logical to look at front-end components (ball joints, tie rod ends) that may be badly worn, and/or a tire balance problem.

Or, this could be related to an engine problem.
Is the Check Engine Light illuminated?
Does the shudder continue (even briefly) after you pull over on the road shoulder?
If the answer to either question is “yes”, then your mechanic should focus on the engine.

As to the loud thump underneath when reversing, if this model is a RWD vehicle, then I would suspect a badly-worn u-joint in the driveshaft. If it is a FWD car, then you might want to think about the possibility of worn motor mounts and/or transmission mounts.

Thanks! It’s going to the mechanic next week so will get him to check all those suggestions.