A6 2006 Quattro vibration

**Tinkywinky** · 13-06-2019,11:18 AM

Evening,
i have a 2007 quattro 4.2 avant with air suspension.
125k miles.
bought it with a vibration through the seat but struggling to cure it. vibration occurs at approx 65-75mph. over 75mph and it goes
have had wheels balanced with normal and roadforce balancing.
Have tried 2 sets of wheels/tyres.
have replaced rear discs, which i thought helped but it soon reappeared.
i *think* (but cannot guarantee) it does reduce if i put into neutral when at this speed.
suspension components look to be okay.

I think it needs a 4 wheel alignment - is it possible this might cause a vibration at speed?
i don't think its had a gearbox or diff oil change.

my thoughts....
4 wheel alignment?
control arms/wishbones?
sticking caliper piston?
propshaft?
driveshaft?
diff?
gearbox?
flywheel?
engine mount?
tyres - think i have ruled out.
wheel balancing - think i have ruled out.
wheel buckle - think i have ruled out.

apart from the vibration it goes well. just annoying when travelling at highway speed.

any suggestions on where to start?
cheers.

**Scott K** · 13-06-2019,12:27 PM

Try and get it scanned for faults. Any chance it could be a misfire from old injectors? Also could be the torque convertor. I would have thought the most likely candidate was the tyres / wheels or driveshaft / CV joint.

**Tinkywinky** · 13-06-2019,12:37 PM

thanks for reply. scanned with VCDS and no faults.

i've tried dropping down a couple of gears at the same speed to see if its RPM dependent or speed dependent - but not drawn a conclusion on that...

i never though of torque converter or CV joint.
think i've ruled out tyres and wheels as have swapped over to 2 sets with no difference and replaced one set of cheap ditchfinders with some better mid range and had wheels balanced twice.
will try and get a better look underneath at the weekend.

**Tinkywinky** · 13-06-2019,12:59 PM

just to confirm
vibration does not occur through acceleration, only once at 65-75mph.
is felt through seat.
trying to see if it occurs in 4th and 5th gear at this speed to then determine if speed or RPM linked.

suppose that will then rule in or rule out some of the items on here and point more towards engine/gearbox or diff/driveshaft.

**Crasher** · 13-06-2019,03:56 PM

I would check that the radial run out coloured markings on the rear flanges are aligned.

**Tinkywinky** · 13-06-2019,07:09 PM

Originally Posted by Crasher

I would check that the radial run out coloured markings on the rear flanges are aligned.

thank you. is this the connection from the prop to the rear diff?

**Tinkywinky** · 13-06-2019,07:15 PM

Page 2
are these the markings?

thank you in advance.

**Crasher** · 13-06-2019,09:04 PM

Yes.

**54A4Avant** · 14-06-2019,11:14 AM

Any significant rattle from the engine when you start from cold? A failed timing chain tensioner can introduce a marginal timing difference between the two sides of the engine, which resonates at a certain speed. Mine used to do it at about 62mph but after fixing timing chain tensioner, it went away.

**Tinkywinky** · 14-06-2019,02:21 PM

Originally Posted by 54A4Avant

Any significant rattle from the engine when you start from cold? A failed timing chain tensioner can introduce a marginal timing difference between the two sides of the engine, which resonates at a certain speed. Mine used to do it at about 62mph but after fixing timing chain tensioner, it went away.

thank you for the reply. this is interesting.
no noticeable rattles, but very interesting to note.
it is a hydraulic tensioner buried somewhere near the rear bottom of the engine?