Any thoughts on what might be causing a vibration through the car, only felt when accelerating at approx. 65mph on the (smooth) motorway? Vibration ceases above 75mph, and also ceases if I stop accelerating and free-wheel.
Pretty sure it's not wheels or tyre alignment; both were checked on a jig a few months back. And I don't get the vibration at any lower speeds.
Should I be looking at/for engine mounts, or some kind of balancer gubbins that is out of whack?
Car's done 56,000 miles and is otherwise running a treat, (apart from a little oil consumption, albeit no smoke or leaks so not sure where it's going to...)
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I would begin by checking the obvious - mainly to make sure nothing's going to drop off. So, wheels, tyres, suspension bushes, engine mountings, etc.
If all is well with those parts, I would look very carefully at the driveshafts - and particularly the joints on each end.
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>>And I don't get the vibration at any lower speeds.
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First check. Note what revs it's pulling when accelerating at 65, then do the same in a lower gear. If it's genuinely speed rather than engine revolution related, that rules out everything engine related, including mounts, balancer shafts etc.
Now, you say the wheels have been balanced. Have you tried swapping them front to rear? That would rule out everything wheel and tyre related.
After that most likely would be, as the man said, a driveshaft joint being on the way out. Drive around in circles on full lock in each direction and listen for clicking noises. If there's enough play in one to cause imbalance and vibration, it should click.
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Inner joint failure caused similar vibrations on a Pug 306 i owned.
The boot had split letting all the grease out and all the dirt in the world in.
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Thanks folks - I will definitely be looking in to driveshaft joints. I'm 99% convinced it's not engine related. I only drive the car about once a fortnight, so will try the full-lock test and listen for clicking at the weekend...
I intend to live with the problem for another 6 months/4000 miles until its service is due, or am I taking a huge risk?
I daresay Audi driveshaft joints are made of pure unobtainium and will set me back 500 quid-odd come service time...?!?!?!
And whisper it quietly: I haven't changed the cambelt (yet) either..!
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Inner joints don't tend to show themselves on the full lock test, you are barely changing the position of the joint.
If the boot is easy to get at (and the right type that plays ball), it might be worth getting some of the correct CV grease, snipping the largest clip and repacking with fresh grease, a good cable tie is fine as a boot clip, come to think of it the outer joints wouldn't come to any harm either if you work cleanly.
Couple of hours should see all 4 repacked.
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The flaw in that approach is that if it is a joint that's causing the vibration, it must already have worn to the extent of having excess play in it. I would doubt that regreasing will fix it.
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If you don't drive it much, it could just be a flat spot on a tyre.
Last edited by: Alanović on Tue 2 Jul 13 at 16:14
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Audi A4 Cabriolet - 04 2.4 Vibration when accelerating at 65-75mph - Number_Cruncher
