vibration only in neutral
 

'09 diesel. car is smooth in gear but if i shift into neutral (ie rolling at speed such as 30 mph) the car has a mild vibration throughout. any ideas as to cause?

Only while moving in Neutral at 30mph? Or also while standing still with engine on?

only when moving, not when standing still. PS-30mph was just as an example, its not only at 30

Boy that sounds odd.

When you are in gear you are loading engine, trans and driveline. When in neutral, all you have is driveine and part of the trans.

Can you see if you can duplicate the vibration WHILE IN GEAR by carefully applying small degrees of accel or decell?? Does braking impact this at all? light brake?

A bit of a WAG, but Id look at engine and trans mounts and all thrust arm bushings.

The very tricky part is that we KNOW that visual inspection of BMW bushings is not fool proof- there are common bushings that fail, causing odd vibrations, but look AOK.

HTH

Diesels have "active" engine mounts that are soft at idle and hard when the car is moving,controlled by the ECU.These car were never engineered to be moving while on neutral,so what you describe is not part of the normal operation.There may be a problem,of course,but i would say if the car feels Ok under regular driving conditions the vibration may be because of the motor mounts function.

wow. they sound expensive. ;)

thanks all. will let you all know the outcome. dealership has it today for this and a few other items

I wonder how did you find out the issue to begin with? Driving and put in neutral?

was heading down a long stretch of hill, decided to pop it into neutral and coast to perhaps save some fuel. ended up getting the vibration as soon as i did it