2010 CC Intermittent Steering Wobble @65+mph - suspect rack?

[jwpalfrey]

Hi All,

I'm hoping someone can shed some light on my problem so here goes, my car is a 2010 Passat CC TDI GT 114k miles, fitted with Eibach 25mm springs and 19" aftermarket wheels.

The problem I have is an intermittent vibration through the steering that becomes apparent above 60mph, it's intermittent in that only certain road surfaces aggravate it but increased speed makes it worse, it doesn't get better above 70mph.

So firstoff I've had the car up in the air and checked for wheel buckles.flat spots, none
I then had wheels balanced, this did not help.

So I swapped fronts to rears, this helped a little.

So I then recently got the car up in the air again to check for suspension play, or bearing play, I cannot feel any however I did notice that there seems to be play from the steering wheel to the rack, with the front end in the air wiggling the steering from side to side there is a audible "knock" as slack is picked up from side to side.

This seemed odd to me, the "play" is not clear cut in terms of looseness, it feels damped slightly like a bush has worn.

It's really odd as there is no play in the track rods or suspension and the wheels feel tightly connected via the rack which makes me think I have play in the rack to pinion gear. However the "damped" nature of this play is what confuses me.

There's another oddity, If I run the engine (to get the rack to operate assisted) with the wheels still in the air and then wiggle the steering side to side quite violently as the play in the rack is felt at the wheel you can feel and get a side to side vibration as the motor assists the rack a little one side to the other, This didn't feel normal at all.

So here's what I feel like is happening, there is play in the rack which is being exaggerated at speed (due to minor rotational inbalances which would not be a problem if the rack had no play) however with this play the motor "see's" the rack moving and so assists it a little and this culminates in the rack vibrating side to side as the driver input (though the column) cannot stop it due to the play in the rack, culminating in steering wheel wobble at speed.

Playing with the DCC also seems to help a little sport mode being where this issue is felt least - I assume due to the lower assistance level.

I've heard of subframe bushes and bolts, could this be my issue?

Fundamentally the car is ok to drive but seems to have lost the precision in the steering as input in line with the damped play felt. Just trying to work out what it could be before I inevitably send it to an independent specialist to look at it.

Any ideas welcomed