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Differential Question

Two months ago, I changed the Differential Oil on my '04 325i... I have since checked it for leaks on a few occassions and have found none. 3 or 4 weeks ago I checked the oil level (by attempting to add to it) and it was at "full"... (and YES, I torqued the drain & fill plugs back to spec).

This morning, and just before exiting the Freeway at my regular exit I thought I smelled that unforgettable Gear Oil odor... Wishfull thinking led me to think it might have been another car. A couple of miles later and when I got home and exited the car, I could tell that it was my car that put out the odor in question.

I just went out to the garage and as I moved it to a spot where I can jack it up (so I can check fluid level and how much of it has leaked out)... but I can hear it making this sort of humming noise that seems to be coming from .... yes, the rear axle area - Differential.

Not really sure how to go about diagnosing it (instead of OR before taking it in to a shop)!!!
Do I drain what's left and look for metal shavings?
Do I drop the whole differential, open it up and check for damage?

Not realy sure what to do or what to look for. Any input would be greatly appreciated.

Last edited by 3-2-5-i; 06-12-2006 at 10:10 AM..
Old 06-09-2006, 02:42 PM
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What makes you think it has leaked other then the smell? Have you checked it yet to see if any leaked out? Did you replace, or at least reuse, the crush washer on the drainplug? What fluid did you use, brand and viscosity?

Cut an under shirt in half and drape the cloth over a clean pan. Drain the diff into the pan then pull the edges of the shift up to filter the oil and check for shavings.
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Old 06-12-2006, 08:10 AM
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First, let me thank you for responding.
Quote:
Originally posted by Jeron
What makes you think it has leaked other then the smell? Have you checked it yet to see if any leaked out
There is some residue on the Differential Cover, and there are a few drips on the floor directly beneath the Drain Plug & where the Cover & Gasket are located. (Not sure whether itís leaking from the Drain Plug or between the Differential and itís cover).
Quote:
Originally posted by Jeron
Did you replace, or at least reuse, the crush washer on the drainplug?
I replaced it with a new one I picked up from the Dealer.
Quote:
Originally posted by Jeron
What fluid did you use, brand and viscosity?
I used Mobil 1ģ Synthetic Gear Lube LS 75W-90 <--- Link:
Quote:
Originally posted by Jeron
Cut an under shirt in half and drape the cloth over a clean pan. Drain the diff into the pan then pull the edges of the shift up to filter the oil and check for shavings.
I was getting ready to drain it right now. Iíll do that and post what I find.
Thanks again,
Old 06-12-2006, 10:08 AM
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Make sure to check the level before you drain it.

Put another new washer on the plug, clean up the diff cover and check for leaks every couple of days to try and find where it's coming from.

75w-90 is correct. You don't need the LS but it wont hurt. Many companies put LS additive in all their gear oils.
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Old 06-12-2006, 10:14 AM
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Quote:
Originally posted by Jeron
Make sure to check the level before you drain it.
Since thereís no way to view how much Gear Oil is in there now, I was gonna drain it and use an old bottle to see how much came out. Thatíll work, right?
Quote:
Originally posted by Jeron
Put another new washer on the plug, clean up the diff cover and check for leaks every couple of days to try and find where it's coming from.
Will do. Hopefully, that humming noise will go away once I refill it. And if so Iíll be checking it every day to make sure itís OK.
Quote:
Originally posted by Jeron
75w-90 is correct. You don't need the LS but it wont hurt. Many companies put LS additive in all their gear oils.
Well, according to that Mobile 1 webpage, the Gear Oil I used already has an LS additive (and hence the ďLSĒ in itís name. Hereís a quote from that page:
Quote:
the Mobil 1 Synthetic Gear Lube LS 75W-90 contains special friction modifiers designed for limited slip-type differentials. In most applications, the addition of special LS (limited slip) additives is not required.
Thanks again
Old 06-12-2006, 10:34 AM
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Pull the fill plug first then reach in with your finger and see if you can reach down to the oil level so you will know how low it got. If you cant reach the level of the oil then it is very low. Yes, you can measure it with a bottle either way.

If it isn't very low then I would just top it off and clean it all up and start looking for the leak. Once you find the leak then do a final oil change.

I'm surprised you could smell it while driving. Is it leaking from the half shaft seal, onto the boot, then slinging onto the exhaust, then burning?
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Old 06-12-2006, 10:45 AM
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I'm curious why you were changing the diff oil on an '04? BMW recommends changing it at 100k miles, I think, while more conservative estimates put it at 75k. Have you already racked up those kinds of miles? (I've only got 23k on my '03.)
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Old 06-12-2006, 03:19 PM
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Quote:
Originally posted by Jeron
If it isn't very low then I would just top it off and clean it all up and start looking for the leak. Once you find the leak then do a final oil change.
Well, I guess I am 0 for 3 .
First, and after squeezing every last drop out of there I came up with about 1/2 a Quart (Full capacity is 0.95 Quarts).
Second, upon close inspection of the white rag I used, I can see that it had some metal shaving... very little but they were there none the less.
And lastly, I did catch a few pieces of -what seemed like- rubber. (I say "what seems like" because I picked a piece of that up and it felt pretty flexible as well as stretchy).
Quote:
Originally posted by Jeron
I'm surprised you could smell it while driving. Is it leaking from the half shaft seal, onto the boot, then slinging onto the exhaust, then burning?
It's actually leaking from around the Differential Cover Gasket (Why? I haven't a clue) And from there, I could see that as it splattered, a few drops hit the Muffler although most of what leaked out was splashed over underneath the spare Tire well (beneath the trunk).

Anyhow, I'm not really sure how damaged it is on the inside (or is it safe to assume that "metal shaving" (and although I could only see a few) EQUALS "a shot Differential???")...

What I might do is take it off, open it up and visually inspect it from inside. I mean the car is not drivable either way... not until (at minimum) the gasket is replaced OR (worst case scenario) the Differential is rebuilt or replaced.

Any ideas on where I'd be able to get a few price quotes? New, used or rebuilt?

Any and all suggestions are welcome!!!

.... in fact, donations will be considered as well
Old 06-12-2006, 07:03 PM
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Quote:
Originally posted by epbrown
I'm curious why you were changing the diff oil on an '04? BMW recommends changing it at 100k miles, I think, while more conservative estimates put it at 75k. Have you already racked up those kinds of miles? (I've only got 23k on my '03.)
Actually, according to BMW (at least for an '04... not sure about an '03), the Differential Oil as well as the ATF in the Tranny are "Life-Time-Oils"... i.e. need NOT be replaced (for who's lifetime though?) {My guess for the lifetime of their 48 month/50,000 mile free maintenance period}.

And yes, your curiosity is warranted. I have approximately 78,000 miles on my '04 (purchased it in December of '03). I can see that you live in Chicago (Brrrr...) and my guess is that you have a "winter beater" that you drive around six months out of the year. I, on the other hand, live in the Los Angeles area where the sun is shining 335 day out of the year. My daily commute adds up to about 100 miles a day and I've been known to take a drive up or down the coast on a regular basis...

I have been chastised for it before but hey, I bought a nice car so I can drive it... not just look at it
Old 06-12-2006, 07:29 PM
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Quote:
Originally posted by 3-2-5-i
And yes, your curiosity is warranted. I have approximately 78,000 miles on my '04 (purchased it in December of '03). I can see that you live in Chicago (Brrrr...) and my guess is that you have a "winter beater" that you drive around six months out of the year. I, on the other hand, live in the Los Angeles area where the sun is shining 335 day out of the year. My daily commute adds up to about 100 miles a day and I've been known to take a drive up or down the coast on a regular basis...

I have been chastised for it before but hey, I bought a nice car so I can drive it... not just look at it
Umm, my 325i is my winter car - I drive a 2003 Z4 during the warmer months. And I feel the same way - I bought them to drive, not pamper But you do a HECK of a lot more commuting than me - until Novermber, I could walk back and forth to work, it's so close.
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Old 06-12-2006, 11:44 PM
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Lifetime my a$$, you cant go wrong changing your diff fluid. Don't go more than 50-60k but heck it only holds a qt and its easy so change it every 2 years.

I would replace the gasket and drive it until it starts making noise.

If you end up replacing it consider two things: rebuilt/used units and limited slip. I'm pretty sure E46M3 LSD will not work but there must be one that will, maybe even the E36M3 LSD. It wont be hard to find out what you need to get a LSD in there.
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Old 06-13-2006, 06:54 AM
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I plan on dropping it, cleaning it, replacing the Gasket, refilling it and then reinstalling it.

Hopefully that humming whine/noise it was making will dissipate until I can find a good replacement.

Thank you, Jeron. Your input has been invaluable. I'll post an update as things progress.
Old 06-13-2006, 09:47 AM
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You're welcome.

Make sure you are certain which seal is leaking. I would suspect one of the input or output shaft seals is more likely to leak than the housing seal. Also, you should be able to replace the seal without removing the diff.

Good luck.
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Old 06-13-2006, 10:00 AM
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I am fairly certain that it's a Cover Gasket leak.

And as far as replacing the Gasket while the Diff is on, and out of the 8 bolts that hold it on, 2 are not easily accessible due to the "vibration absorber" being there. Considering I should torque those bolts to specs to avoid another leak, I would prefer to go the long route by dropping the entire unit. Plus, it allows me better access to cleaning and inspecting it internally.

Thanks again.
Old 06-13-2006, 10:19 AM
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Another question;

Are there any products out there which one can use to clean/flush a Differential?

I found SEAFOAM Trans Tune which according to their Consumer Support people can be used in a Differential. However, the Diff must be in place and in working order for the cleaners to be effective.

Considering my Diff is cuurntly off the car and since I'd like to clean it prior to reinstalling it, I was hoping for some sort of spray or liquid that I can use in there.

A few people have recomended "brake parts cleaner" or an "engine degreaser" but my concern is that the solvents/chemicals in those products might be a bit too harsh for the seals and bearings inside a Differential.

Others have suggested a fill-drain-fill process might be all that is needed in this case.

Any other ideas?

Thanks in advance

Last edited by 3-2-5-i; 06-21-2006 at 09:46 PM..
Old 06-21-2006, 09:32 PM
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