Since there's no reference whatsoever in this forum about differential servicing, beside occasional advices "needs to be done", "do all front/C/rear at the same time", etc, etc, I decided to put together a thread...
Probably it will be unimportant for people who have done it, but I take my chances...
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I had/have a "rattling" noise right after start-up for quite sometime, and when I changed the oil on 12/23 I finally traced it to the "transmission" area.
After reading more about it, I suspect/ed the differential, although I haven't touched it yet ever since I got the car.
In the hind sight, it makes now more sense why I have all the "oil" leaks in that general vicinity. I'm pretty sure now that my flange and rear seals are shot, as I read these are extremely common for the ZF models used in the C4s.
I purchased some synthetic 75w-90 (Mobil1) and today, poised by a gung-ho attitude, I got the car on the ramps. I knew exactly where the fill plug is (per Bentley), so ...Bonzai!
Man....what a progressive disappointment...
1) No drain plug
- Back in the house to look again in Bentley... "Drain" plug still pictured in the stupid illustration..."WTF?" I thetorically asked myself..
Got on the forum and searched...not much (as said before); Got on AudiWorld - C4 forum (thanks), and found indeed plenty information, although without pics or a diy. C4s - indeed the front defferential has no drain plug; not that's important much.
Also, it sounds (and after going back under the car, it also looks) like are two alternatives:
a) Remove the CV axle, AND the flange (and have the opportunity to change the seal - however difficult it may be without the proper VAG tools); or
b) Remove the downpipes/cats.
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2) My WalMart ramps don't "lift" the car high enough on the garage gravel floor, so I'll need to find a different place to do it, with a concrete floor where I can raise it higher.
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Hence I'll continue the thread when making some progress on the matter.
I had also two unrelated discoveries:
- Found the source of the "thuds" I experience, even after replacing the struts all-around: a control arm bushing
- Although I was living under the impression that my ZF box is FLE (when I changed the ATF 1 1/2 yr ago didn't bother to wipe clean the serial number tag), in reality my ZF box is:
4HP18CJE. Needless to say that I let out another WTF?...
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(to be cont'ed)

 

By the way, Bob, Jim, HCW, or whomever else with C4s that have changed the seal/s, do you guys know by any chance the part number/s for the seal/s?
(is there any other seal -a "rear" one in the heat shield area? I know I mentioned it, but is just a supposition as there's no mentioning of it in Bentley)
Thanks much in advance.

 

If we are talking about the seal on the output shaft of the transmission. I have replaced both of mine on my 02-A6 and 00-A8.
BTW- I though the idea was they they drain themselves, usually on my driveway

The front final drive has no drain on mine either I just filled it until it dripped out.

Over time the rear trany seal sags at the bottom allowing oil to seep by. I don't know if your model has the heat shield on the tail of the trany but easy going on the removal or you will break it when you break the bolts loose. Might be a good idea to spray it good first and have some aluminum scraps and a rivet gun available to put it back together somehow. The new seal probably wouldn't last long with the heat from the exhaust pipes right there.

Do yourself a favor either go to Audi for the seal or order it from world impex I also think ecstuning has them too. Both mine were the same part and it shows yours as being the same as well. part # 018409399B

Here's a couple links

http://www.ecstuning.com/Audi-C4_A6-...rain/View_All/

http://www.worldimpex.com/search_by_...9399B&x=40&y=4

 

Jack,
yes I'm talking mainly about the front final drive - so passenger side.
My pos is not a Quattro, so I deal only with the "front".
I see now that left side (driver) can also develop a leak - why am I not shocked?, and apparently there's a leak inspection hole below the drive flange.
I guess I need to check that sucker out too, which I hope is not leaking. From what Bentley shows, that seal is behind a bearing on the drive axle, which drive axle appears to come out anyway. The illustration is with the TConvertor out, so makes you wonder how the f. could you slide the drive axle back in the tiny whole inside the transmission without seeing what you're doing?
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- I don't want to speak foolishly, but the Intermediate Drive appears to be on this non-quattro a "sealed" box - the tail of the tranny you're talking about, I bet? - which propably has a gasket, instead of a seal. After "re-intalling" they talk about refilling with ATF, so I'll have to check that out since I'll pull down the cats/downpipes anyway.
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Thanks much for the seal part #. Cheers

 

OK, mine are quattro so That doesn't help you much. Funny how that hole where you would normally tap and install a drain plug has a purpose... odd

Lets see I don't think we need a drain plug just a hole so we know when it leaks


I can tell you that my front axles seamed to wiggle around when I was playing with the front final and it freaked me out. Apparently there is play in those so that would be normal. It's a real nice thing to know before you grab those and start seeing dollar signs

 

Ok...
It took me a while to sort through unclear information. Some vendors have no idea, same as some dealers... Some dealers don't want to share the part numbers, like is a big f. mystery... Finally I got a nice dealer that gave me the right parts.
Also, I e-mailed on a whim ZF North America, and a very nice gentleman (thanks, Steve Jaffe) provided me with the ZF part numbers, although I can't do much with them since the ...ZF distributors don't carry those parts!
Is a strange world out there, believe me...
Nevertheless, here's what I found:
- 01F409399 -> Left (driver) side seal
- 01F409400 -> Right (passenger) side seal
Both of these are listed only for Manual Transmission on lots of part vendors' websites, but according to Audi are listed for my automatic box as well.
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- 018409399B -> is listed as Rear AT Seal, and I don't need it since my POS is not a quattro (4WD).
- 016409399B -> listed as Output Seal, returns on lots of websites the same item as the one above it -sounds like are interchangeable part #s.
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Lastly, The ZF part #s are as follows:
- Left Side seal: 0750111195
- Right side INNER: 0750111126
.............OUTER: 0750111262.
As aforementioned though, I wasn't able to find anything via the ZF route. I may call tomorrow the "corporate office" in Vernon Hills, IL and inquire about parts, since it is the place that distributes the parts/kits to the distributors...LOL
It may take a while until I get my parts and start tearing the stuff down.