clrA6

This is a picture I took tonight under my car, I recently noticed this when it was on a hoist a few weeks ago. I dont know what is leaking? Transmission? Rear differential?? I have no idea, all I know is that I need to fix it and I want to know what it is before I go fixing things. Also, there is a nasty burning smell coming through the vents when vehicle is stopped sometimes, no smoke, just the smell... could this be the culprit? Any input on this problem would be greatly appreciated. Thank you.

A6Gary

Hard to tell what you're looking, e.g., looking forward or reverse? From the picture, it would appear that the leak is oil, which might mean the rear main seal is leaking. And if you're leaking engine oil and it is dripping on your exhaust pipe(s), then you'll smell it.

zwopunktacht

Don't get the complete picture, but I would start looking very closely at the input drive shaft seal of the rear differential.
Differential gear oil sprayed on the hot exhaust during driving might be the cause for the smell.

For reference (it shows the details from an A8): http://www.audipages.com/Tech_Articl...placement.html

I had mine done at 120'000km.

DLCroft929

The picture you posted is of your rear differential. The wet spots are most likely caused by a small/minor leak of gear oil. Its hard to tell where the leak is coming from beacuse the area is dirty. Most likely the leak will be from either the rear differential input shaft seal or one of the rear axle output flange seals. If you degrease and clean the area first, then drive the car a bit it will be easier to tell where the fluid is leaking or seeping from.
P.S. I did refer to it as a small/minor leak because you did not indicate that there was any fluid or wet spot on the ground beneath the car.

AUJ

The rear propeller main seal has been redesigned. Some put in the older style because of the much cheaper price assessing the demonstrated longevity since purchased when the car was new. Clearly, like the ATF, it is not a lifetime part.

clrA6

Thanks so much for all if the replies and suggestions. The picture is from the rear of the car looking towards the front. I had my boyfriend take a look at it and he got some of the oil on his hand to try and see what it is, but to our surprise there is a fluid (probably differential fluid) and also a grease that is much thicker than the fluid...(maybe from the boots on the axles?) If it is the differential, will that be okay to just make sure the level is okay until I can afford to fix it? And as for the grease... What kind of damage could that be causing? Also, when he was looking at it he said it looks like whatever is leaking has been leaking for a long time...

zwopunktacht

Here are my suggestions:

1. Clean the rear differential housing and check the rubber boots around the drive shafts for tears or missing clamp.

2. Check fluid level in rear differential as described on the last page in this doc:
http://www.audipages.com/Tech_Articl...eckingrev1.pdf