MP4.2+6.0

1. Check wheel bolts just in case.

2. After that, I would tend to be on same page as you about the CV joint. But as you say/know, those don't tend to be particularly temperature sensitive. You might continue to suspect the wheel bearing too. Not just the bearing, but also the bolts that hold it to the whole steering knuckle. On my C5 4.2, the dealer replaced a front wheel bearing under warranty, and one of the four retaining bolts backed out like 50K miles later; made a horrible racket, there because it ground against the CV joint stub axle. That was why I also asked about history of any wheel bearings--not just the bearing, but also those bolts that hold the bearing cartridge assembly in. Mister Bally is also right to mention the inner CV bolts, just in case those are loose somehow. From the factory I wouldn't think any of the bolts are compromised, but again in any old repair history involving the area, a mechanic may have not torqued fully, didn't replace bolts, didn't use LockTite in lieu, etc.

Failing any other resolution, figure you may have to take an educated guess that it is the CV joint. The Lobro OES types are not that expensive these days. If I pulled it on my own, I would be tempted to do the wheel bearing at the same time since most of the disassembly is the same.

Net, pray for wheel bolt simplicity. BTDT back in my C1 days, so it happens.

awdinut

Here's another clue for you all...I checked the bolts and all were torqued to 90# , nothing loose. I have also noticed that backing to the right causes the same problemon in the left front corner...the wheel on the outside of the turn is the left one in that scenario.

So its not just on the right side and I think it defies odds that both CV joints developed this odd temp related problem at the same time. So there needs to something common to both sides and that would only be a differential would it not ?

And another small clue refinement: after making the turn that I always make, and which has been precipitating this problem, I only drove as far as the end of the parking lot and replicated the turn but evrything was normal. So it doesnt even take the few blocks to make the problem go away for the day as I had previously thought.

It was borderline on the required temp today at 30F, so the phenomenon was not as pronounced (read scarry) as when in lower temp. I walked along side the car as my friend did the manouver but could not see any odd movement of the wheel. I will try watching again on a colder day. I've got to get to the bottom of this and it seems a tech doent have any idea how to find the problem.

Is it the center diff that locks up for the first 3-5mph and caused the need fot the tires to scrub while making a turn-from-stop ? And is that controlled by a computer which would leave a code if malfunctioning ?

MP4.2+6.0

It does increasingly seem like it is differential related from what you are reporting across different wheels of the car.

The center differential is called "Torsen" and unlike many AWD vehicles is purely mechanical. It has various advantages over a lot of the electronic or Silicone fluid clutch pack stuff--which are fundamentally reactive systems. This cite isn't necessarily 100% Gospel on some of what it says, but probably close enough: http://en.wikipedia.org/wiki/Quattro...l-drive_system).

Theory aside, I think you are at the point you (or a shop) should get under there and check the fluid levels for all the diffs carefully, especially the center one. If it is low, you undoubtedly have a leak somehow, but at least you can get some fluid in there hopefully before any real damage occurs, plus hopefully find it is just a rear tail seal or something like that. If the levels are correct, you probably need to get to a ZF specialist type tranny shop.

FWIW, I have never had to deal with any diff issues myself on any Audi ever, but I'm thinking the center one is probably removable off the "tail" of the transmission case while tranny is still in the car, if it comes to that. My C4 A6 did have a rear tail seal leak (on the back of the Torsen) under warranty, but I caught that early when I could smell the typical rancid gear oil fluid smell burning off when it would hit the exhaust. The rear seal is accessed basically by just getting the drive tube out of the way; the front seal to it requires pulling the diff off the tranny case AFAIK.

As I type, one more thing dawns on me too, also requiring inspection. I think Audis have some kind of bearing set up that carries that center tube from the Torsen back to the rear. The rear Torsen seal is known to leak sometimes on older ones (like a C4/C5 or D1/D2 era), but if I'm remembering right, issues with those bearings come up once in a while too--not remembering clearly if it results in noises, vibration, clunks or what. You might want to do some searches around these areas. Hasn't come up much on the D3 board, but maybe the D2, C5, C6 or Q7 boards, all of which would have similar set ups (at least with the higher powered motors, typically the 4.2 until the shift to the 3.0T) Also realize this whole area is right above the exhaust, so warms up quickly. Fits your temp related observations.

audicatt

I have something that sounds similar on a 2017 A7.
it’s quite extreme and making the car undrivable.
I’ve attached a video of the car driving at low speed - you can hear the noise and juddering.
any advice gratefully received!