leaking differential? help

[xcashewx]

ive noticed that when i park my 230 on flat ground overnight in the morning there will be a light almost clear grease coming from the differntial. i cant tell exactly where the oil is coming  from but it drips right below the driveshaft on a metal plate right underneath it, it doesnt look like any seal is leaking from what i can tell from just looking and feeling on it. i have also noticed while reversing and when the car downshifts when braking i can hear a quick "knock" sound is this something bad or just normal?

[waqas]

Hello,

There are two likely possibilities for this leak.

The first is the pinion seal located at the front of the differential, where the pinion emerges and attaches to a flange, which in turn attaches to the drive shaft. If this seal is leaking then you should see a trail of oil from right underneath the front face of the differential to the point where the oil drops finally break free.

The second is the oil breather tube that sticks out vertically from the top edge of the joint between the left axle tube and the differential. This typically overflows if the oil has been over-filled (or if you recently hung your car upside-down).

There is a small felt pad inside the breather that acts as a filter or damper. This can get clogged over time, and the resulting high pressures that build inside the differential eventually cause the pinion seal (the next weakest link) to fail. So you might be looking at multiple things.

Also, if the oil is clean then it might be difficult to trace the path.

The knock sound can have many sources (also unrelated to the differential), so can you narrow down the source? (front/rear/left/right)
Possibilities include motor mounts, transmission mounts, subframe mounts, idler arm bushing, differential upper mount, muffler 'donut' mounts etc, etc.

[xcashewx]

the knocking noise comes from somewhere at the differential or driveshaft because you can hear it and feel it when it knocks

[psmith]

I cleaned the differential including the vent shaft and refilled it with the car on the ground and axles horizontal and my leaks have stopped. 

I would guess that the klunk comes from either the differential mount or the exhaust donut hangers as Wagas said.  That's where my klunk came from.

[xcashewx]

i cleaned out the breather it was clogged and switched out the oil. i filled just at or a little beneath the fill mark and ive only discovered one small drop that leaked out. and as far as the clunking, it never does it unless hard braking, down shifting in a low rpm and shifting from 2nd to 3rd when using minimum throttle

[ericlee]

Hi, can anyone tell me how to remove the cap of the breather?  it is crushed vry tight on three sides, I am afraid that I will break something if I pry hard.
Thanks
Eric

[Benz Dr.]

We seem to have two different things goinmg on at the same time.

 Don't remove the cap on the vent. Clean around it and blow throught it to clear it out. This is a normal maintance item we check on every car regardless of year or model.

  You ( the other guy I think ) may have a bad mount bushing right on the differential. This is the one that's right in front of the hinge for the two main parts of the axle. You pretty much have to remove the axle to repair this. As part of the job I usually go throuh the whole axle unless everything appears to be in good shape. It's not a small job.

[J. Huber]

Now I am confused... ok not a stretch... I sort of recall having to pop off a metal cap to get to the little mesh pad/filter. It was a pressure fit, crimped a bit that I was able to work off with a little effort. Dan, are you saying that I did not need to do that? Its been a while so maybe I am imagining things?

[Benz Dr.]

I see no reason to remove the cap. I use compressed air to blow through from the threaded end. If there's anything in there it will usually end up all over your face.

[don p]

Not sure if it was the right thing to do but I
 used brake clean on rinse mine out then air to dry it.

[Benz Dr.]

Not sure if it was the right thing to do but I
 used brake clean on rinse mine out then air to dry it.

  I think that would be OK. Always be careful when working with compressed air though, it can do you serious harm.