i am posting this for my dad alcazar who is in france.
when he puts his foot to the floor at 70-80mph the whole car vibrates. when crusing at the same speed (constant speed) its completely smooth. it dosen't seem to be wheel related and dosent appear to be related to boost on or off.
any one got any ideas what this might be.
TIA Alcazar's son.

 

Most probably the wheels need balancing. usually get the shudder around 60-70 mph will probalbly go away at around 90 MPH.

 

btt
its not wheels out of balance any one else? need help.
alcazars' son

 

The brake discs maybe warped

 

Warped braked discs would show as a pulsing through the brake pedal, when it is pressed

Whereabouts is the noise coming from? and has it just started to happen?

 

May be the axis need re-oiling.

 

Is it always at the same engine speed (RPM)?

I dont think it will be anything mechanical, its probably a missfire if it only happens when your flooring it.

 

I've had this before on another car, it was a CV joint or driveshaft joint worn, as torque is transfered through the joint it twists off centre creating an imballance, lift your foot up, torque reduces, shaft sits back in middle.

worth a try, fixed my problem.