Apparently the Audi gods have decided I'm an ******* and have looked down on me badly, in the form of either a failing driveshaft center bearing or a worn diff mount. I'm leaning strongly toward the failing driveshaft, as it is very reminiscent of when the CSB failed on the driveshaft in my 300ZX - thumping at certain RPM or under extra load, such as going uphill or accelerating, and some vibration to accompany it. It could be the diff mount but I'm not hearing a specific clunk when shifting so I'm thinking driveshaft.

Anyone changed this out, whether to rebuild/replace the bearing, or just replace the shaft? For that matter, has anyone replaced the diff mount? If so, any pointers or lessons learned that you can share? TIA...

 

Ehhh, i would think about your diagnosis. I have only replaced two driveshafts on an audi for a clunk, BOTH of them unseccessufully fixing the noise. The center bearing (carrier bearing) is easy to replace, but you need the alignment tool when installing the driveline. You "might" get the driveshaft back where it was before by doing it by eye, but if you mess up you will end up with a larger vibration than you started with.
If you indeed blew up the carrier bearing it should have visible damage to the rubber areas. You could also try gripping the drive line and move it up and down, side to side, it should NOT move.

 

Yeah i would wonder more about a mount or a loose exhaust. My exhaust was loose so that only at driving at certain angles would make it bang around.. Hopefully it isnt a bearing, I always thought they were a pain to replace and it sounds like they are according to auditech. The vibration doesnt really fit with those i guess though so idk..

 

Good info - that's actually kind of encouraging that the shafts aren't known for failure. I'm going to get under there after work this week and see what I can find. I'm assuming that the mounts for the various drivetrain parts (diffs, transmission, etc) are stiff enough that I shouldn't be able to move any of them much, if at all. Do you know offhand if the alignment tool is available for purchase or if it's a dealership-only tool? Finally, if not the bearing, what is more likely? Center diff or transmission mounts? It's definitely coming from below and behind the driver's seat, az I can feel it through the seat and hear it behind me, but I understand that those sensations can transfer down the driveline. Thanks man - I appreciate it.

 

Transmission mounts, engine mounts, or snub mount. The tool is huge, and most people NEVER use/need it so i don't know. Its made of aluminum so i would imagine its stupid expensive. You might also want to check the torque on the subframe, if you ever loosened the subframe and didn't replace the bolts, that could be the problem. Those bolts are a stretch design, meaning they can only be used once. Alignment techs will loosen these bolts and not replace them when doing an alignment also.

 

Alright - yeah that does make sense about the tool but I figured it was worth asking. My snub is only a few months old so I'll get under the car and inspect the other mounts to see which ones warrant replacement. Thanks again for the input - nice to have a voice of experience here

 

hey. Did you get this figured out? My Audi is doing the same - under a load - especially going uphill and through a a curve at the same time. Or if you really wind out the gears - nothing insane - I have yet to have this car above 80 on an interstate - it does that easily.
But if I am super careful - story book clog up a catalytic converter grandma driving - no clunk.
Love driving this car and want to get this figured out. Thx in advance

 

For me it was a worn transmission mount - apologies for not closing the thread way back in 2010 when I wrote it lol.

 

No worries. I appreciate the reply and your description is actually the closest so far to what I am experiencing.
I'll have my son-in-law look at them and see what he thinks.
It seems so intermittent but I am assuming temp and humidity affect the mounts - or maybe what's left of them - and that's why it acts up more on some days than others.
Or... Maybe I'm flipping crazy.
Thanks again. I appreciate it.

 

Sure thing. Also, if they are compromised to the point of shifting, they may end up in more or less "solid" positions at times, which could also result in you feeling more or less of the sensation at times. While he's under there, have him look at the diff mount too - that's another fairly-well known wear item as the miles accumulate.