TheAvgBear

Bit of backround:
So after I purchased my allroad I drove home (~2 hr drive), I parked it in my garage and was just looking over things. I had it idling and I noticed there was a puddle forming on the ground. So i rolled underneath it and it appeared to me (first time audi owner) that the output shaft was leaking (which it was as well). So i did my research and i went about replacing the tailshaft seal. I put it all back together and went for a drive, but noticed that it was still dripping and making the puddle. During the output shaft seal change I learnt that the gear oil for the diff is honey color. The fluid on the ground was a reddish brown color (The previous owner had used the Castrol LT71141 ATF, which is red). So it must be transmission fluid. I looked under the car and this is what I seen,


The left side of the pic is the tranny pan, and the right side of the pic is towards the rear of the car.

Just left of the gear fluid drain plug is a shiny piece that looks cleaned (due to the leak I imagine?) and dripping. It looks like there is a paper gasket inbetween the two housing secitons there. But my confusion is why the tranny fluid is leaking from there? Shouldnt it be gear fluid? There is a few other spots that look like they have pretty big drips hanging off of them as well, so what could be causing these leaks?

It is leaking fairly badly I'd say, here is a picture of the puddle that formed after about 20 mins of idling in my driveway, 10mm wrench for scale (Note, there is a slight slope on my driveway so it kind of started to run):




I also feel I should mention that a transmission fluid cooler line that wraps around the front of the engine's oil pan is dented pretty much flat. I doubt fluid could pass through it, maybe a small amount. Could this be causing built up pressure issues? and causing a leak farther back on the tranny?

While i was under the car I also noticed that this sensor on the front edge of the tranny pan is leaking as well. Not sure what sensor it is, or if it could be related at all but i thought i should mention it:




I apologize for the large post. I am pretty worried about the condition of this transmission as i havent put much mileage on it since buying it (the car already has 183,000km or 118,000miles). I seem to keep finding more and more leaks, I hope it isnt something major. So if anyone has any insight on this it would greatly appreciated. I pretty unfamiliar with audi and their massive transmissions haha but I'm eager to learn. My plan is to hopefully solve these leaks, replace the dented line, then replace the filter and add new fluid.

jjrichar

The sensor you have is actually the main plug to the sensors and solenoids inside the transmission. If it's leaking here, you will need to get replacement O rings for the plug. This can be done when you do the filter, but I think the valve body needs to come out to be able to remove the plug and the O rings. This is starting to get a little bit involved if you aren't familiar with the setup.

Unless the breather hole on the top of the transmission is blocked, which would be very unusual, there should be no pressure inside the transmission cavity to push oil out. It's probably just a seal somewhere that is shot. This can either be simple or a nightmare to replace, but you are stabbing in the dark until you can identify exactly where the leak is coming from. Clean up everything, and get underneath to see where it's coming from.

Definitely replace the crushed pipe. This is going to hinder the oil cooling which is critical. I wouldn't think it would create a leak, but I'm not entirely sure.

PetrolBear

Uh, it is very ugly. Very uncommon....and unsafe for the Tiptronic... do as jjrichar wrote.
Question is, why do you have leaks at uncommon places and why the tip cooling line is dented? Both are uncommon and refers to something frumpy work around the tranny. Just prior to selling? You could/should take a notice towards the seller and he should cover all of your costs (at least).

TheAvgBear

Thanks for the insight, I appreciate anything I can get right now. I took your advice, and spent a good hour cleaning absolutely everything up. And then I let it idle to see exactly where it was coming from. Its leaking from ontop and trickling down the side to the bottom, basically right along the seam that separates the central diff and the mid housing.

Before idling, cleaned up:


After idling:
https://i.imgur.com/yCufmNA.jpg

Side view of the left / drivers side:


Another shot:


The puddle that formed after 10-15 minutes of idling:


#1=central diff
#2= Mid housing
#3= Transmission

TheAvgBear

The cooling line looks like it was just dented when someone parked to close to a curb at some point. I have a new one and am ready to replace it.

There was some work done to the tranny before I got it. The previous, previous owner unknowingly let the gear fluid leak out of the output shaft seal to the point where it got so hot it smoothed out the teeth on the output shaft, and became immobile, so they sold it for cheap to a friend of mine. He took it to a transmission shop and they diagnosed it/replaced everything that needed replacing. Then I came along and bought the car. The tranny feels great, and shifts awesome (for the small amount of time that I've actually driven it).

The only thing ive noticed that looks fishy while underneath that area that was worked on, is it looks like there is a red goop or adhesive where there should be a green paper gasket. I dont know if maybe this could be causing it to leak? Its odd that it is atf from there, and that it is leaking out from that high up.

PetrolBear

i advise do not try to fix yourself. Take the car back to the tranny shop.
BTW, there should not be any kind of sealant material (glue) only the new greenisch paper / composite seals (in the OEM and aftermarket kits). So if you see adhesives at the edges, they did an improper work. Basicly there should be a warranty on such kind of work! In Europe there is 6-12 months of warranty on such servies.

jjrichar

From the pictures, the leak doesn't seem to be coming from the transmission but from the center diff. Have a look at the video link below of one of these being pulled apart. I don't know why it's red. It would normally be a honey colour like you say. I'm not sure if you can fix this with the transmission in the car. Personally I would be filling both the center diff and transmission to see which takes oil to confirm where the leak is coming from.

TheAvgBear

I just wanted to update this post for anyone that was curious. I think I found where the leak is coming from.. A friend of mine hooked me up with the center diff housing, and the mid transmission housing from his parts cars so I could have a look at them. In the mid housing there is two seals, one that keeps ATF on the tranny side, and another adjacent seal that keeps gear fluid on the diff side of things (I believe these seals are 01V 409 400a, and 01V 409 400b. Respectively. They are on order right now, so i will confirm when they arrive). I noticed on the driver side of the midhousing (where my leak was coming down from) there is a small hole, that leads right to the middle of these two holes. I have no idea why, but im assuming its to divert ATF out of the transmission rather than back into the diff, if one of the seals were to fail? I also noticed that my gear oil is darker than I expected it to be. I recently changed it, so maybe ATF is leaking back into the diff as well?

Here is a pic of my leak, running down the drivers side of the boundary b/n the central diff and the mid housing:
#1) Central Diff
#2) Mid housing


Here is a pic of the extra mid housing I just got, the seal on this side is the 01v 409 400b (you can also see the inside lip of the 01v 409 400a 'brownish' seal just on the other side of this seal):


And here is the little hole, that leads right to the center of those two seals:


So now I just have to educate myself enough to replace these seals. Any info or tips on that would be greatly appreciated.

Bo

There are 2 seals: one in the aluminum housing (01v 409 400a) and one inside of the shaft (01v 409 400b). Outside seal 01 v 409 400a
01v 409 400b - centerline of the seal must be aligned with the hole in the shaft
01v 409 400b - seal inside of the shaft





[QUOTE=TheAvgBear;24665169]I just wanted to update this post for anyone that was curious. I think I found where the leak is coming from.. A friend of mine hooked me up with the center diff housing, and the mid transmission housing from his parts cars so I could have a look at them. In the mid housing there is two seals, one that keeps ATF on the tranny side, and another adjacent seal that keeps gear fluid on the diff side of things (I believe these seals are 01V 409 400a, and 01V 409 400b. Respectively. They are on order right now, so i will confirm when they arrive). I noticed on the driver side of the midhousing (where my leak was coming down from) there is a small hole, that leads right to the middle of these two holes. I have no idea why, but im assuming its to divert ATF out of the transmission rather than back into the diff, if one of the seals were to fail? I also noticed that my gear oil is darker than I expected it to be. I recently changed it, so maybe ATF is leaking back into the diff as well?

Here is a pic of my leak, running down the drivers side of the boundary b/n the central diff and the mid housing:
#1) Central Diff
#2) Mid housing


Here is a pic of the extra mid housing I just got, the seal on this side is the 01v 409 400b (you can also see the inside lip of the 01v 409 400a 'brownish' seal just on the other side of this seal):


And here is the little hole, that leads right to the center of those two se


So now I just have to educate myself enough to replace these seals. Any info or tips on that would be greatly appreciated.