Transmission noise

Hello fellow mechanics!

"For some time now, I've been noticing increasingly loud noises coming from the transmission in my A3. The noises are particularly noticeable at very low speeds (between approximately 40 and 70 km/h), regardless of the gear selected. This, in my opinion, suggests a problem with the drive shaft (differential) or the bearings of the main transmission shaft. The difference between the noise produced during acceleration and deceleration is minimal. The noise is best detected when the car is rolling (with the clutch disengaged), as the engine noise is less dominant then."

I noticed the following links in the knowledge base:
/viewtopic.php?t=3970
/viewtopic.php?t=3656

In my CZL gearbox, there is definitely no hollow shaft installed on the left side.
Could the thing about the transfer case actually be true (MJ 1997), or what?
Okay, the current mileage is 140,000 km.

The gearbox appears to be sealed, and there is no visible leakage from the shaft seals or flange seals.

Who has ideas and suggestions?

Regards,
Alex.

Hmmm...

Unfortunately, I don't have an answer to your problem either.
I also experience a grinding noise at speeds of approximately 20-60 km/h.

Since it's an A3, it probably wouldn't be a bad idea if...
Please post this in the A3 forum.

Sure, here's the translation:

"Best regards."

Another question: Have you considered the wheel bearings? 140,000 miles doesn't necessarily indicate transmission damage, as long as there are no external leaks. Transmission fluid level checked; a change might help, if it's not the wheel bearings.
A differential could also be an option...

Hello everyone,

Well, it's definitely not the wheel bearings, because I had a wheel bearing failure on the front axle just about 5,000 km ago, which of course was fixed. And I can only emphasize that the background noise was completely different.

Regarding the differential: Is it possible to replace the differential relatively easily, without having to disassemble the rest of the transmission, or is the design more complicated and unfriendly?

@Julian:
I initially thought about changing the transmission fluid, as that would likely be the cheapest solution if it makes a difference.

"Does anyone have experience with gearbox repair work?"

Thank you in advance.

Regards,
Alex.

Regarding wheel bearings, I can add that they tend to become noticeably louder when cornering, whereas the transmission is less likely to make that kind of noise (unless there's a differential problem).
(disconnected, or 'N' - then it's clearly audible.)
My mileage is already at 165,000 kilometers, but they should still last a while. (Not everything that's said is necessarily true.)

As long as no gears pop out or someone tries to engage a gear, I would leave it at checking the transmission fluid level.

What is the sound of the transmission when the car is stationary/idling, with and without the clutch pedal depressed?

Hi,
My Audi 100 also has a similar "constant" noise, but at speeds of 70-100 km/h, which is probably due to the additional cylinder.
The transmissions are, of course, completely different from those in the A3.
For me, an oil change didn't make any difference. There weren't a particularly large amount of wood chips in the oil.