Advice for Differential?

[melloh]

Lately I've been hearing some noises coming from the rear - louder and faster with increased speed (and unrelated to engine speed as it remains unchange if in neutral/idle at speed).

At first, I thought/hoped it was just wheel bearings.

But, when I went under to check my rear brakes, I noticed the diff had a wet look - telling me the diff has a slow leak (there has never been a drip or pool of oil).

So, my theory has changed - is the noise really coming from the diff?  (Also to refute bearings, it does not change or get worse during turns.)

I know it at least needs a top-off of oil.  But, how hard is it to repair?  On e21s there's one main gasket that usually is the culprit, but I have been unable to find the corresponding gasket for this diff's design as there are many more gaskets!  I have some pics and it doesn't appear to be leaking from the left or right output, but I'd like your expertisesss.  Can a driveway mechanic like myself accomplish this by myself, or am I better off sending to a mechanic.  Also, what price range might I expect to pay for a BMW indi?

Thanks in advance!

[ak96ss]

The very first thing I would do is clean it. You can't tell where the leak is coming from when the whole thing is caked in goo.

Then, check again after a fair-to-middlin' length drive. I would bet a donut that the diff is not in fact leaking - that looks like oil that has migrated down from an engine leak to me.

It may be leaking, but there's just too much junk on there to tell where.

If worse comes to worse, I have an open 4.10 diff for sale...  

[melloh]

Ha ha... good point.  I guess I didn't want to clean it because

1) I just spent 5 hours tinkering with the wur from my e21

2) and I didn't want to 'destroy the evidence'

Let the de-gunking begin... (can't wait til I can afford a steam cleaner!!!!!)

[D. Clay]

If it's coming from the front of the differential it's a pinion seal. This does not necessarily mean the pinion bearing is bad. Check for pinion backlash by turning the driveshaft. Mine has play and will turn freely about one eighth turn.
You can rock a wheel at 3 and 9 o'clock with the car jacked up and see if the rotor moves in relation to the caliper. If it does, it's play in the bearing. If both are bad, they'll make noise even when turning.

[melloh]

A few questions to help me visualize and clarify:

1) I only need to jack up one wheel (not both rear), yes?

2) should the car be in gear or with the parking brake on?  Fron what I gather, it seems having the parking brake one would hel pme see if the shaft will give any.

Thanks for your input.

[Vladi]

Most chances are your profile gasket has gone bad. I've had a 4.27 with this exact gunk "shield".
33.11.1.210.428    this is the part number for your gasket.

[melloh]

If it is this gasket, what's the difficulty level in replacing it?  It looks MUCH more involved that what would be required for the e21...