Leaky differential

[Goodguyili]

Hello 8ers, I got a 3.64 open differential that was installed by the previous owner that has always made a small stain underneath it from a leak. Im not exactly sure where it's coming from. Looks like it maybe from the top or from the output shaft area. The previous owner's mechanic said that its got a some kind of breather valve on top of it and that has been left open. He said that whenever he installs differentials, he always fills it up until it drips out of the fill hole then seals, but I'm pretty sure that isnt true. It's leaking somewhere.

Anyways I am looking for a gasket kit to reseal my differential, but I'm struggling to find any that actually exist. What can I look for to help seal my leaky diff? Thanks for reading my dilemma.

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[petejk]

Output shaft seals are easier to replace than the pinion shaft (input) seal.

If you wipe the leakage off the diff and drive for a few miles you may be able to determine which seal it’s leaking from.


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[shogun]

the breather valve must function, that is important because air has to come in or out depending on temperature if the oil. Example pic https://www.ecstuning.com/b-genuine-...e/33107857501/
Gaskets and other parts are available from the dealer http://bmwfans.info/parts-catalog/E3...wse/rear_axle/

[Goodguyili]

Output shaft seals are easier to replace than the pinion shaft (input) seal.

If you wipe the leakage off the diff and drive for a few miles you may be able to determine which seal it’s leaking from.


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Yeah I'll try and do that, it's gonna need a lot of wiping in the mean time. Im not home right now, but here's a photo of the leak. By the way, what kind of diff oil would you use?

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[Goodguyili]

the breather valve must function, that is important because air has to come in or out depending on temperature if the oil. Example pic https://www.ecstuning.com/b-genuine-...e/33107857501/
Gaskets and other parts are available from the dealer http://bmwfans.info/parts-catalog/E3...wse/rear_axle/

Thank you for letting me know where to find some gaskets. I wasn't sure where to order some because I couldn't find any online, but I completely forgot about asking a bmw dealer. The car leaks while it sits, so I doubt it's coming from the breather valve, but I appreciate you letting me know how it functions.

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[petejk]

75w90 for open diffs, 75w140 for LSD as far as I know.

From your picture, it looks like it could be leaking from the rear cover


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[shogun]

Rear cover leak, or could be the output shafts are leaking, what is usually the case, and when driving the oil flows backwards by air turbulence and even up the rear cover. Output shaft seal kits are also available from aftermarket.

[Goodguyili]

Rear cover leak, or could be the output shafts are leaking, what is usually the case, and when driving the oil flows backwards by air turbulence and even up the rear cover. Output shaft seal kits are also available from aftermarket.

Okay. So I looked online and I found that the OE numbers for those you spoke of:

Output shaft seals & rings - 33107510289
Differential cover gasket - 33108305033

Are those the only parts I'll need? Or should I replace other stuff while I'm at it. Keep in mind I do want to save money where I can. Thanks for the input Shogun. Also do you know what's the best way to handle differential seals, this will be my first time doing this procedure.

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[petejk]

This is a good write-up for seals replacement:
https://www.bimmerforums.com/forum/s...rial-with-pics

There are a few extra parts listed in the write-up, such as gear oil, and the rear cover gasket

[shogun]

and some more pics, output shaft seal is the usual place which leaks http://bmwe32.masscom.net/sean750/di...OutputSeal.htm
also check the input seal from driveshaft side

[dragon850]

It looks like your speed sensor o ring is leaking....
You do not need to remove the diff to take care of that.
O ring is about 2 bucks.

[Goodguyili]

It looks like your speed sensor o ring is leaking....
You do not need to remove the diff to take care of that.
O ring is about 2 bucks.

I swear if that is the problem... I already ordered 2 output shaft seals. Well that sounds like an easy fixing, can I order it at an autoparts store or do I need to order it online as well?

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[dragon850]

Its probably a bmw part, check ecstuning.


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[Goodguyili]

Well, I decided to take out my diff to work on and it was a heck of a job to take it out without removing the subframe. But I did it. I used an O2 sensor removal tool from home depot to access those really akward angles

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[petejk]

Getting it out is the hard part. Working on it now will be a piece of cake.
Are you any closer to seeing where the leak is coming from?


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[Goodguyili]

Getting it out is the hard part. Working on it now will be a piece of cake.
Are you any closer to seeing where the leak is coming from?


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I am VERY certain it's coming from the diff cover. As i was about to undo it, half of the bolts were loose... hand tighten I assume. Looks like the PO or his mechanic rushed the installation of this 3.64 diff and forgot to tighten it. Nonethe less im going to replace the seals all around since it's out already.

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[Goodguyili]

Well today has been a doozy. I installed the differential back in and took the gal for a spin! She flew on the pavement and sung like a car that's been sitting on 4 month old gas . Fortunately i did put fuel stabilizer because I knew this car was going to sit for a bit.

...however, while I did fix my differential leak, now I got a fuel leak right where I stuck the fuel check valve underneath the fuel filters. So I'm probably going to need either new fuel hoses or a new T flow valve.

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[Goodguyili]

Here's the new leak. Looking at it it seems like its spewing, but thats all water I drove over and splashed from underneath. I'm pretty sure under fuel pressure its a slow drip coming out of that T valve and a hose that isnt tighten enough or has a crack I didnt anticipate for.

[Timm]

Great work - but you need petrol-line clamps rather than Jubilee-Clips:

Fullscreen capture 10122020 132502.bmp.jpg

[rjjablo]

If you are getting gas on the bottom of the tank it is likely that the lines on the top of the tank are leaking. 4 of them and the easiest way is to drill an 1-1/4 to access the clamps. 3 Lines are normal and one is extra big and you have to order the hose.

[Goodguyili]

Great work - but you need petrol-line clamps rather than Jubilee-Clips:

Fullscreen capture 10122020 132502.bmp.jpg

Back to the rescue yet again! Thanks Timm, I will assess that asap.

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[CaifanSC]

It looks like your speed sensor o ring is leaking....
You do not need to remove the diff to take care of that.
O ring is about 2 bucks.

When you say, "you don't need to remove the diff to take care of that"...are you referring to the speed sensor o ring? or the output flange seals? Or both? Doing a little reading on this same issue. Great info here!

I had the same two issues as the original poster...but inverted. I fixed a worn out fuel line and did all new lines and filters....and then...I noticed a few dark fluid drops under the rear of the car. Weighing my options at the moment to see if I just take care of the leaks with the diff in place (if possible) or remove the diff and do those things....and then mission creep into center bearing/guibo replacement, rear suspension refresh, etc.

Le sigh. First things first, gotta pop it up on ramps, clean up and see what exactly is leaking...as I also do more reading and ask questions .

[rjjablo]

Speed Sensor O-Ring is easy to do with the Diff in the car

Output Flange seals require the Axles to be unbolted, I don't know if you can get them off with out moving something else

I would replace the two crush washers for the Diff Drain and Filler bolt and the Speed Sensor O-Ring, clean it up and see if it continues to leak

Rear cover requires the diff to come out. I would say its easier to drop the entire subframe versus trying to drop just the diff

2K just for all the parts on the rear end. You need an Impact, Torch and 12 ton press at a minimum