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Hi my 2007 S type diesel has a strange intermittent vibration through the vehicle at speeds between 30 to 40 mph. if i accelerate harshly it does not appear. Any thoughts anyone?
the car has done 140,000 wonderful almost trouble free miles.

Firstly the simple stuff:

Are all the wheel nuts tight, have had this happen twice with other Cars, only noticed on the over run, once when Garage hadn't tightened Nuts and secondly a few weeks after Wheels had been Powdercoated, Nuts bite into the new coating, then gradually became loose and needed re-tightened.

Bulges or defects on Tyres.

Warped Discs.

Engine Mount rubbers split/worn.

Propshaft Joint rubber coupling (doughnut)

Doug.

Thanks Doug I will check your suggestions and get back to you

Warped Discs.

Engine Mount rubbers split/worn.

Propshaft Joint rubber coupling (doughnut)
Hi Doug
All the above checked and all ok. My expert has cleared all fault codes to see if anything turns up on my next visit to get the flexi joint on both cats repaired

I recall there is an intermediate "plummer block" type bearing half way along the prop shaft. If that were gone you would certainly get vibration.

Don`t forget the obvious wheel out of balance issues that can occur at various speeds or tyres that might have flat spots. Cheap tyres of uncertain parentage and perhaps poor construction can be problematical.

Mike

HI Guys The latest is, my expert thinks it might be the torque converter. no fault codes present, the fault is intermittent with all gear changes smooth as silk. i will be consulting my local gearbox man soon. The plot thickens.