Diff Leak Location? (photo included)

[jeffjassky]

Hey, y'all. Got my first Z3 a few months back and have since noticed the classic "diff whine" issue. I found this single photo in a recent service record that shows the diff case is leaking. It was not addressed at the time of service. Being a newbie I'm looking for insight and maybe some encouragement! While I'm at it I have a question:

Based on the photo where does the main leak seem to be coming from?

My newbie eyes tell me it's the main gasket - but wanted to check with y'all before I start ordering replacement parts and potentially borrowing tools.

 

[Eddie Zedder]

I would say one (or both) drive shaft seals. Oil wouldn't track back from the cover joint towards the front of car, unless it's been driven backwards at speed regularly

 

[t-tony]

But if the driveshaft seals were leaking there would be oil below the shaft(s). I would say it is the backplate gasket, but, I would clean it all down with brake cleaner and run it for a bit and re check before doing anything.

Tony.

 

[Pingu]

It's the main gasket seal that is leaking. It has moved forward by diffusion (usually, but wrongly, called osmosis). It's how water climbs filter paper.

 

[Eddie Zedder]

But if the driveshaft seals were leaking there would be oil below the shaft(s). I would say it is the backplate gasket, but, I would clean it all down with brake cleaner and run it for a bit and re check before doing anything.

Tony.

Fair point Tony, should have looked a bit closer

 

[jeffjassky]

Thanks, everyone!

I swapped out diff the fluid this afternoon and sprayed down the entire area with brake cleaner. I'll check it every so often to see if the leak is still active at all.

Fingers crossed that the fluid change helps with the diff noise. I'll update the thread after a few hundred miles and let you know how it's going.

Thanks again!

 

[jeffjassky]

If anyone wants to know about the diff oil - I ended up using Royal Purple 75w140 just because my local O'Riley's had it - though I personally wouldn't specifically recommend for or against it at this point.

I spent two hours reading through forums and found a real clusterfunk of information with conflicting data and reports and no clear consensus on what to use - which is understandable considering there are actually several variables that may be worth considering (diff design, climate, use of vehicle, etc).

I have the 2002 3.0i which I believe has LSD. However, from what I understand, there may have been several diff variants that were offered (different drive ratios, different designs, torsen, etc) that prefer different oil weights? It was not particularly clear and I could not identify precisely which one I have without taking off the diff cover.

Ultimately, I parsed that practically any 75w140 "gear oil" should with "friction modifier" be considered "safe" for both Torsen and clutch pack type LSDs. Considering how bad the grinding sound was I figured that simply changing it to anything fresh would be an improvement over where it was. If it needs rebuilding down the road I'll revisit the oil question once I have it disassembled.