Vibration at speed

[Lerichard]

I am currently chasing the cause of a vibration at speed in my V70.

The car is a 2005 2.4D 163 E3 with the 5sp Geartronic auto, fwd. 121k on the clock.

The car's vibration presents similar to that of an out-of-balance or buckled wheel. It becomes noticeable around 35-40mph and at its most abrupt at 75mph. It is felt mostly through the steering wheel but throughout the car generally, making it unpleasant to drive and uncomfortable to ride it. It is dependent on road speed, not engine speed, most obviously under throttle load but also present on light throttle/overrun/braking.

I found that a couple of the alloys (Orestes 17") were buckled so were replaced and the whole set re-balanced, but the issue persisted. Unfortunately this wheel swapping has resulted in 4 different tyres (which I hate) but at least all are in good condition.

Subsequent research pointed to driveshafts and tired bushes as potential causes, so I have had replaced both front wishbones (which were original and tired) with Lemforder replacements, and both driveshafts with new SKF items. Frustratingly this hasn't sorted the issue.

I recently replaced the lower engine torque mount as the inner bush was shot, but no improvement resulted. The top engine mount has a bit of play, so may get replaced at some point. The 3 main mounts appear OK from my limited inspection.The engine itself is a peach so I suspect no issue there.

I'm less trusting of the gearbox since becoming increasingly aware of the AW55-50's fragility since buying the car. On the move there are no issues with the box - it shifts smoothly enough with no odd behaviour. When shifting between PRND at standstill there's some vibration when engaging gear but nothing I would deem excessive given the car's mileage. There is a very slight delay in the box engaging drive when pulling away after sitting stationary with the footbrake applied, and being too hasty results in a thud. I understand the box drops itself into neutral when stationary so suspect this is a quirk rather than an issue.

Incidentally, I recently carried out an autobox fluid change - the deposited fluid wasn't excessively dark or burnt-smelling and there was no swarf on the plug. The fluid level before and after have been measured as correct via the dipstick.

So I've reached a bit of an impasse. I can't help but suspect a gearbox/diff issue as I'm running out of ideas. Any assistance would be appreciated.