Diff oil seal leak?

[roadvoyager1]

Whilst checking under the car the other week I noticed oil contamination around the inboard drive shaft coupling to the diff. There is more contamination than shown in the photo below as the shaft is rotated and some oil has flicked onto the underbody.

Having spent a fair amount of time searching forums etc, I have found very little information about this type of leak and would appreciate your comments on my thoughts and if I am right or not, and how to repair.

To help with the location of the problem I have included a couple of screen shots from RealOEM also

Oil leak


Output shaft picture


Output shat text

Drive flange picture

Drive flange text

The oil is coming from the output shaft gasket (left element of 6 in Pic 1) and the drive flange (1 in Pic 2).
I think that the shaft seal with lock ring (6 in Pic 2) has failed.
From what I have read, to release the output shaft the 6 torx screws (3 in Pic 1) are removed and the shaft is then free to separate from the drive flange which can then be pulled from the diff housing using a 3-leg puller and some spacers.
To remove the shaft seal there is a lock ring (10 in Pic 2) which is a circlip that sits inside the inner groove shown on the shaft seal. Can anybody confirm this or explain the actual arrangement/method please? Are there any parts other than the oil seal and lock ring that must be replaced at the same time?

Thanks in advance for any guidance you can give.

 

[Low Rider]

@Lee might be able to help out with this issue

 

[roadvoyager1]

@Lee might be able to help out with this issue

I was hoping @t-tony, @Brian4, @Brian H, @Antm72, @gookah or one of our other resident mechanical experts may be able to chip in on this one.
Failing that if anybody has the relevant pages from the Z3 Bentleys Manual they could photograph and post that would be most helpful.

 

[t-tony]

Hi, I've never done this job but following the exploded view you posted I would agree with your perspective. If I were to do this I would most definitely replace the "O" ring (no. 9) where this assembly contacts the diff. housing while I was doing it.

Tony.

 

[Brian H]

Not sure this is a diff leak, the flange on the diff is sealed so no oil can get through there. There is a brake hose above the output shaft, is this leaking? Other thought is that it could be grease leaking from the CV joint?

 

[Antm72]

I would say the circlip actually fits on the output drive shaft.
They normally have a circlip set up to stop them popping out it's not like a circlip more just a sprung steel band that locates in a groove on the shaft to lock it in or it would just fall out.
Found a picture you can see the groove on the shaft it locates in to...

It doesn't look like the diffs leaking the oil it is on the wrong side of that flange it would show behind it in my view.

 

[gookah]

Yes I would agree, that is not where I would expect a diff oil seal leak to show. It would show on the back of the output shaft rather than on the half shaft.
I would say it looks like grease transfer from the gaiter on the cv joint nearest to the diff. Check those gaitor clips.
You diff looks to be dry as a bone.

 

[roadvoyager1]

Many thanks for all of your feedback. Took the car into our local independent garage, real old school place with a mechanic who has around 30 years on the clock. They regularly work on older cars like the Z3. The verdict was that it is not a leak from the diff seal, if it were the oil would be on the back of the output flange (so he agrees with most of your comments). Possible grease from the CV joint but he advised that it looks like old contamination and suggested we clean it off and check it again in a few weeks to confirm it is not an active leak.
As always great support from our forum experts when a call for help goes out.

 

[t-tony]

Many thanks for all of your feedback. Took the car into our local independent garage, real old school place with a mechanic who has around 30 years on the clock. They regularly work on older cars like the Z3. The verdict was that it is not a leak from the diff seal, if it were the oil would be on the back of the output flange (so he agrees with most of your comments). Possible grease from the CV joint but he advised that it looks like old contamination and suggested we clean it off and check it again in a few weeks to confirm it is not an active leak.
As always great support from our forum experts when a call for help goes out.

Sounds like a good plan. Hope it turns out to be nothing.

Tony.