Differential Oil Leak

[PeterPortugal]

Hi All,
My differential is emptying itself out all over the garage floor. It was a filthy mess which made it hard to work out where the leak was coming from but after a clean I think I have found it. It seems to be weeping from where the rear axle tube is bolted to the differential casing as per the pictures. Is there a seal between these parts? What sort of a job is it to change it out? I am envisaging substantial !1Are their any other possibilities bearing in mind where the oil is showing itself?

My car is a 1963 W111 but I assume the diff is the same as a 230sl from this era.

Best wishes to all

Peter

[PeterPortugal]

Close up

[ja17]

Make sure it is not the rubber axle boot or its clamps. That is the normal source of leaks. Also, if the diff is over-filled, the oil can be forced out the vent at the top and drip down to the area you show. The seam (in you r picture) is not the usual source of a leak. You might try tightening those bolts a bit.

[PeterPortugal]

Hi Joe,
Thanks for your advice. The oil in the diff has leaked to such an extent that you can't feel a level at all with your finger in the fill opening. I had the car worked on by a specialist and he replaced the rubber boot and the oil. I would have assumed he didn't overfill it. I will check the fitting of the rubber boot though just to be sure and try tightening the bolts. Thanks again
Peter

[perry113]

Make sure the car is sitting on the ground when you set oil level. If its jacked up and you fill it to the filler you will be overfilling it. I use 2X8 wood planks under the rear wheels with the car on the ground if you don't have a drive on lift that gives me enough room to sneak under the car to fill and set the level.
Clean the rear end up and then give it some time to see where the seepage is coming from.
I had an issue with my boot leaking because the clamps were too loose. The new clamps from Mercedes were essentially impossible to get tight enough. I was able to come up with 9mm width zebra hose clamps that worked perfectly to resolve the issue. These clamps were hard to find and I ended up buying them in large qty so I have a set if you need them.
Let us know how you make out.
Peter

[Benz Dr.]

We had a 190SL in a couple of years ago that had a leak where the axle tube was screwed on to the diff housing. and it destroyed the gears so we had to do a lot to fix it. So, yes, they will leak at that joint.

[PeterPortugal]

Thank you all guys I really appreciate you taking the time to post. I will get to it tomorrow and report back.

[Benz Dr.]

There is one other place they can leak and it's not pretty. Aside from the boot and oil seals, the diff housing can be broken from careless workers. In this case, the right side axle can be dropped if you don't have a jack under it while changing the right shock. This will result in a leak that will appear as though it's coming from the large side of the boot. Replacing this part or the clamps will not fix this and it will be hard to see unless you pull the boot back out of the way and have a good look.

In the one case where I saw this, it had a nice bit sized ( big mouth in this case ) chunk broken out that was all in one piece. I believe the center section of the rear axle is cast or maybe ductile iron and it can be welded back into place. However, the axle will need to be removed and taken apart to do the repair. The left side axle tube would have to come off and the crown gear removed. In short it's a big job for such a small repair.

Not likely your problem but worth checking none the less. I think Joe has posted about this and may be able to add his thoughts.

[PeterPortugal]

Well after further checking and cleaning the leak is definitely coming from where I originally posted it was coming from. I have tightened the bolts a touch more but this required a tap with a lump hammer so they were certainly not loose.
In order to fix this I assume I have to separate the axle tube from the diff casing and replace some sort of seal. Is this an axle out job?
Regards
Peter

[Benz Dr.]

There isn't any seal in that area and is sealed with compound instead.  Pretty much have to remove the axle to do this repair.

[PeterPortugal]

Thanks Dan - do you think a bit of high temperature silicone applied externally would work as a temporary measure? I have all the bits needed to do a Getrag 5 speed conversion and planned this for next Winter. Repairing the diff would be a good fit to do at the same time.

[Benz Dr.]

I'm guessing that silicone won't work. I'm thinking there may be products that would work, but I don't have any names for them.
 You have to consider the possibility of a leak while driving and then burning up the gears before you realize you have a problem. If you decide to do a temporary fix, make damn sure it's a dependable one or don't do it all.

[PeterPortugal]

Hi Dan - as per your cautious approach I have decided to opt for the axle out option. When the problem is properly identified I shall post the details.
Regards
Peter