40k service and "mystery" noise

[Jon B.]

Instead of bumping/adding to another post that's kinda unrelated I figured I'd start my own.

My car went in for a 40k service last Thursday/Friday, and I still don't have it back. While it was getting this service done, they were also making up some things they missed on the 30k. Namely the diff fluid and spark plugs. This was a service done by the previous owner, as I have only owned the car since ~late Nov/early Dec. I made sure to have them check those previous services as I've been having a droning noise under load for basically the entire time I've had the car.

I had the shop foreman ride around with me to show him the noise I was worried about, as well as an issue with the TC light coming on randomly and what I assumed was a wheel bearing going bad. They found the bad wheel bearing, and stated it was indeed causing the phantom traction control light but they were more concerned with figuring out the droning noise.

This leads us to today, when I was informed they pulled the "center" diff fuse while driving and noticed the noise go away completely. Now, this is a Haldex car, so I'm assuming they mean that? I didn't want to pry, and they didn't have their main tech/foreman to talk to me so I'm assuming the service writer is just a little confused. I'm hoping that it's just a haldex/diff issue and I get a new one and all is good. But I was curious about what else they could have "pulled" that would cause an obvious change.

Car is all stock, and this is being covered by Audi as far as I'm tracking. I mentioned the noise in one of the tire threads, as I run staggered Conti Extremes instead of the crap Pirelli tires.

Thoughts?

[Chris F]

Make sure it's not the transfer case failing.

It will sound like a wheel bearing (sort of drone) but not go away when you turn left/right like a wheel bearing would.
As it gets worse you will get grinding noise at low speed and especially when fluid is cold.
(effectively you are hearing the sound of the gears inside slowly self destructing)

Mine failed broke a tooth off the pinion inside (freak unlucky manufacturing defect?) had to get a new one out of pocket which REALLY sucked.... (it's not a cheap part)

[o1turbo30v]

If they pulled a fuse it’s not the “center diff”
, they pulled the fuse for the Haldex pump. Most cars have a drone coming from the back/rear diff in parking lots/slow speed while turning.

Interested to hear the issue if one exists.

[Jon B.]

If they pulled a fuse it’s not the “center diff”
, they pulled the fuse for the Haldex pump. Most cars have a drone coming from the back/rear diff in parking lots/slow speed while turning.

Interested to hear the issue if one exists.

It would make typical drone at low speed as you noted, but this was more pronounced at speed under load. Would go away entirely off throttle.

Make sure it's not the transfer case failing.

It will sound like a wheel bearing (sort of drone) but not go away when you turn left/right like a wheel bearing would.
As it gets worse you will get grinding noise at low speed and especially when fluid is cold.
(effectively you are hearing the sound of the gears inside slowly self destructing)

Mine failed broke a tooth off the pinion inside (freak unlucky manufacturing defect?) had to get a new one out of pocket which REALLY sucked.... (it's not a cheap part)

The wheel bearing was a separate issue. It was 100% a bad bearing.

[arulrs3]

Just check the VCDS AWD acoustic wiring logic. Factory setting is Standard and some change to increased traction and Haldex would cry after taking abuse for little longer :) Just a place to check to make sure factory settings are there to troubleshoot.

[Jon B.]

Welp, looks like I might be joining the "Haldex Failure" master thread. They're not ruling it out, but it definitely seemed like they're likely replacing the entire unit Haldex + Diff based on my last conversation.

I'm not super thrilled, but I'm also not paying for it! I'm just ready to not have a boring Audi to drive again. It's been a week and this A4 is a snooze.

[Jon B.]

Car is getting picked up tomorrow as I wait on the replacement diff. Anyone have the most current revision (if there is one) for the RS 3 rear diff?

While I'm not thrilled it's getting replaced, I am happy with the dealer not giving me the run-around. They're absolutely doing their due diligence in trying to make sure I'm satisfied and the car is complete.

[Jon B.]

Picked up the car today. Didn't get a real update as they didn't close the service yet so I don't have paperwork to reference. I do notice it's quieter for sure. The wheel bearing was definitely causing a lot of the things I was noticing.

One thing I found funny were the distance to empty numbers from the RS 3 vs the A4 loaner I filled up today as well. A4 said 570 miles to empty (highway) and the RS 3 climbed as high as 390. I'll take the RS mileage everyday over that A4! Man that car was boring.

[Jon B.]

Finally back and fixed. Whole rear diff replacement definitely made the difference finally. Hopefully nothing else is needed for a while!

[Flying Pig]

Jon B,
Glad to hear the problems were fixed. It’s nice to read happy endings - especially when it involves a dealer performing competently and professionally!

Pig

[Jon B.]

Yeah, they really realized that I wasn't an owner that was going to overlook shoddy work. I dropped it off this week to get that done and mentioned that it had a new noise they created when it was in last. As in, I dropped it off without that noise, and picked it up with it. So it was something they did. The service advisor said he made the tech(s) drive it multiple times to ensure it was 100%.

[vanvan]

Quite old thread, but I have the same issue and since I don't have the option to replace the whole diff+haldex I was wondering if the mechanic was able to pinpoint the location of the issue? Was it the haldex clutchpack, the controller or something in the diff itself?

[mtwallace85]

Quite old thread, but I have the same issue and since I don't have the option to replace the whole diff+haldex I was wondering if the mechanic was able to pinpoint the location of the issue? Was it the haldex clutchpack, the controller or something in the diff itself?

Having had mine fully replaced under warranty, I can almost guarantee OP didn’t get an explanation as to what happened. The dealership most likely won’t know what the issue was either; they install the new one, send the busted one back, and Audi figures out what happened for their own benefit but they don’t share any details. All I got from the dealership was my clutches were binding when it got hot enough but they didn’t know why.

[vanvan]

Thanks @mtwallace85 !

That's good enough info for me.