Quattro crawl + thud/snap when parking/maneuvring

[brandonx22]

Hi there everyone, I will apologize in advance for bringing up a topic that has been beat to death but I have been already trying to look for this everywhere without getting any actual answer (and locally I don't have any capable shops of tracking this down in a timely manner..).
I'm talking about a very big and distinct vibration on my '14 A6 Avant (with stock S-Line lowering, if that matters in any way) and sometimes even a big "thud" sound coming from below (somewhere around the rear axle, I am sorry but I am kind of new to this and I am in no way qualified to properly describe this).
The vibration coming from behind happens when I am cornering at a very low speed, for example 5 km/h, in my garage or around tight residential intersections with parked cars, usually when fully turning the wheel. If the terrain below is disconnected, has rubble on it (say dust/small stones), it's almost guaranteed to happen.
It also happens that I get a very concerning "thud" sound, like some gear-like object slipping and hitting the next tooth unexpectedly. This happens especially when turning the wheel at 100% and the road below is either wet, uneven or dirty with some sort of sand or small stones.
I have also noticed (while being in my garage) that when I fully turn the wheel at times I can also hear a distinct "click" while standing still.
The car has About 180.000 kms on its belt (I acquired it at ~170) and there seems to be no history of any servicing in regards of the quattro transmission or suspension or any parts which may be related. Tires are pretty hard too (it has been sitting at a saloon under the sun before me getting it few months ago) and I still haven't had the need and time to change them.
Considering the fact I have to travel out quite a bit before finding a good shop which can get a look into it, what do my options look like?
How concerning/serious is this? What can be done? What tests can I run myself?
I'll be happy to answer any questions in the least amount of time possible. I thank you for your attention!

[sepheroth86]

If you are getting clicking in the front when turning the wheel. I would suspect c/v axles, control arms or possibly shock mounts.

[brandonx22]

If you are getting clicking in the front when turning the wheel. I would suspect c/v axles, control arms or possibly shock mounts.

Appreciate your reply. I will keep this into consideration and try to do some research...The "thud" sound, once triggered, seems to happen at maximum "fatigue" of the differential and usually happens in the back, but sometimes from the front too. Whereas the click sound, while standing still and turning, seems to come from the front. As far as I know, this car has never had its shock absorbers changed (nor its bearings or any part from that section at all) and overall there is a lot of noise once going over disconnected asphalt and potholes (although I always thought it was due to the 'sportier' ride height)

[sepheroth86]

Try coasting at a low speed in an open are with smooth paving. (put the car in D and let off the brake, no throttle)

Then quickly press the brake hard and quickly let off. Does the car clunk? If so, it is likely your control arms. My car did this, control arm replacement had remedied the issue.

[morski]

is your centre propshaft carrier bearing ok?

[brandonx22]

Try coasting at a low speed in an open are with smooth paving. (put the car in D and let off the brake, no throttle)

Then quickly press the brake hard and quickly let off. Does the car clunk? If so, it is likely your control arms. My car did this, control arm replacement had remedied the issue.

Hey there thank you for your suggestion and taking the time to look at this. Yesterday I tried this on several occasions and the when doing so the car would just make a low thud noise which seemed more to come from the brakes and the whore car locking up. No metallic/clunk sounds, I couldn't hear something "loose" moving if that's what we're looking for, just the sound of the calipers locking it up. Let me know if I did something wrong or I should try to look for something else. Appreciate your help a lot.

is your centre propshaft carrier bearing ok?

Thank you for your reply as well! Unfortunately I have no way of making sure. Could you let me know perhaps if there's anything I can try to hear/feel? Or does it just require a plain inspection on a deck?

[Akakios]

and the whore car

I too call my car names at times.

Take your hand when it's up on stands supported properly or lift, then lift up and down on the center point of the driveshaft by the bearing. Some deflection is normal, lots of deflection is not.

Your best bet is to get us a video of it so we can internet diagnose it for you.

[brandonx22]

Following up: worn and hard tires were causing most of the noise. Switching up to a new set decreased it by a lot.