LiquidRS

I replaced both about 6 months ago as I could feel the vibration, especially at idle. Got them at a good price from www.europeanoempartsdirect.com, c$500 each. It makes a huge difference, when functioning correctly one cannot tell if the engine is turned on or not at idle, there is zero vibration. By the book its a 9hr labour job, so factor that in too. Good luck

DallasDave

All good information, thank you. I am certainly not intimidated to attempt it, but I do not have access to a lift. Damn, just when I thought things were "all good" LOL. I will agree that at idle, my car had a slight vibration but that is all I have noticed. As far as CoD, good to know. I wondered how it got such good mileage on the highway (25+ miles/gallon). I was just about to move forward with the $800 APR tune...I guess those funds will be diverted to this project. Do you think any competent shop can do this or should I find a Audi/German car specific place?

Striker2237

It's not something most would consider DIY, a lift is nearly mandatory unless you have like 3-4 days or really really know the car.

Striker2237

If you get the tune it won't be a factor anymore.......request for APR to lock out 4cyl and start stop entirely so you never will have to worry about smoothness or massively degrading engine life from constantly shutting off the oil flow. Yes yes I know in theory start stop doesn't degrade engine and all those tech brochure headlines but whenever you stop oil flow hydrodynamic bearings transition to boundary lubrication at best. Can't avoid it and it will always wear out far faster in that condition.

You should still be able to average 24-26 and get 30+ highway with the tune. I lost only 2mpg but could and did just adjust my style to gain it back

A8L_New_England

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Haven't heard many reports here or elsewhere regarding that occurring in the 4.0. Can you corroborate that at all?
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It has its share of issues, but a short life of internal components from lack of oil flow doesn't seem to be one of them.
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Turbos excluded, of course
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2turbos4rings

CoD isn’t the only reason for the adjustable mounts, they were in place before cylinder deactivation existed, so you’re leaving some smoothness on the table if you don’t change it. Probably not a ton, but just want to keep the info accurate.

DallasDave

My car does not have a start/stop function, no button, etc. So that certainly is not an issue for me. But I will plan on getting the motor mounts fixed soon.

rechlin

Start/stop is entirely different from cylinder-on-demand. The S8 doesn't have auto-start/stop but it still can switch into 4-cylinder mode to improve fuel economy.

tx170754

Dave,
Just my .02, go to the dealer and let them fix your issue, it is not something that a DYI guy will do it....I've lately sold my A8 with less than 21,000 miles and I'm really glad I did it before going in some expensive repairs....

gk1

In the case of the 4.0T this may not be true.
The 3.0T style (soft/hard) adjustable mounts are different than the vibration cancelling mounts on the 4.0T for CoD.
I do not believe, or rather have not seen, any documentation to indicate the 4.0T also has the soft/hard switchover like the 3.0T.
As others have said and OP is likely noticing, as long as they are not leaking they still perform regular hydraulic mount duty just without CoD damping and it looks like the system also disabled CoD with the fault present so as to not introduce a vibration it cannot counteract.