BMW Front Differential Failing?

[edyvw]

It depends on whether the car has signs of track use - alignment, tire wear, etc. My experience with BMW is out of date to some degree so
I don’t know the cost of a front differential, but I am sure they aren’t cheap, particularly when you factor in labor, and so it would not surprise me that they might look at the service records in the BMW network and pull the engine log. In my experience, BMW gives the customer the benefit of the doubt, but they make a quality product so driveline failures are uncommon and I would not be shocked if they look over the car. I haven’t seen your car so I really don’t know. Some idiots leave the window numbers and inspection stickers on because they think it looks cool . . . .

You may not want to hear this, but if you were interested in a lot of track use, a new BMW is not really a good choice. Too much power and capability will hide the defects in your techniques, and the cost / risk of totaling or significantly damaging a new car is significant. If I were starting today, I would buy a cosmetically ugly E36 or E46, strip the interior, put in at least a roll hoop (can add a cage later if you want to go wheel to wheel in a series like Lemons or AER) and go through the suspension, cooling system, and other wear items. A good seat with proper harness will allow you to properly feel the car and focus on driving instead of restraining yourself with the weak factory / street belts. Keep the power under 200hp and leave the brakes stock, suspension too. This will make you learn. Learn to drive that car at the limit, and if you put it into a tire wall or have another agricultural excursion that is a little
Ugly, it won’t really matter. The car is fixed pretty easily and you don’t have to worry too much about the cosmetics. The new cars, and the new BMWs are so capable that it is difficult to really learn and the reality is that they are road cars - the service intervals and some of the more finicky hardware on the car isn’t designed for true track use, particularly if we aren’t talking about parade laps.

Good luck with it.

E82 128i with stick. It is new track darling.

 

[RAVL]

E82 128i with stick. It is new track darling.

I am dating myself as an old guy. I will go back to yelling at the kids to get off my lawn . . . .

 

[edyvw]

I am dating myself as an old guy. I will go back to yelling at the kids to get off my lawn . . . .

Lol. E36 is long in tooth I would say. E46 for all its advantages when it comes to nimble drive, has issues with rear subframe. It has to be reinforced, especially on track. And considering age, it might be too late.
128 has bulletproof engine (no pesky issue around oil pump nut like on M54), strong chassis, and you can borrow brakes from 335, M3, F30 335/340, get 3 stage intake (I did all that on my 328) and I know some people who lowered weight to some 2,800lbs.
But, I mean, requires DIY work.

 

[m240.to]

Hello friends,

I hope you are all doing well. I wanted to provide an update on my most recent drain interval, which was 264 km with 12,699 unit time. During this interval, I removed the magnetic plugs, as I promised before.

After some simple calculations, I noticed that the differential is wearing out at the same rate as before. If I were to extend the current sample to 1,600 km like the previous one, it would also show 360 PPM of iron. Additionally, there seems to be some amount of water in the oil.

What’s puzzling are the phosphorus levels—they don’t make any sense. The discrepancy in PPM is massive, and cross-contamination seems unlikely since the front differential has a dedicated drain and fill hole, with no need for a suction device. Could it be that my shop mistakenly put G5 in the rear and G4 in the front during my first fluid change, causing this residual discrepancy?

Polaris, the lab I use, has always provided accurate data for everything else regarding this car. However, the data for both differentials (front and rear) looks off and inconsistent, which is quite frustrating.

 

[m240.to]

Attached to this reply, you will find the rear differential baseline and the two samples taken as of the current moment. I'm sure you can see by the data where my suspicion of mixing the fluids comes from.

Photo 1: The data for the two rear differential drains I have done.
Photo 2: Baseline that has to be resubmitted due to water contamination (odd, considering I had these fluids special ordered in order to avoid this from happening and getting old fluid that has been sitting on the BMW parts department shelf. I check the expiry dates of all the fluids and they were all packaged within a 6 month interval and were not due to "expire" till June of 2026).

 

[97prizm]

The fluid in my M240, like all BMWs, is considered "lifetime," but I’m skeptical of that claim, especially for gear oil. Keeping a gear oiI in for the "lifetime" of the car is stupid, and no such thing exists… every single member here would surely agree with me. Anyways, I thought about showing the oil analysis reports to prove something is wrong, but I'm worried BMW might use it against me. They could argue that I did the fluid changes because I drove the car hard, changed the fluid preventively, and broke something as a result of driving the car hard, then tried to get a warranty repair. At BMW’s labor rates, this could easily become a CAD$10,000 repair, even though I could get it done elsewhere for a fraction of the cost, maybe a little more than a quarter. BMW NA isn't as lenient as it used to be, and they might look for any excuse to void the warranty.

If I don’t show the oil analysis reports, I’ll need to change the fluid for a third time at my shop. Both the fill and drain plugs have magnetic plugs, so I would need to put the old ones back in to cover my tracks.

The pan is also upgraded, and although it utilizes original BMW parts, it is original to a BMW M5 Competition. To swap that out as well would add to the cost (all BMW ZF8speed pans are interchangeable, you just have reduced clearance as a result for that specific pan). It's a double edged sword because it is completely un-related to the part where the "failure" occurred, and should hold no bearing in a warranty case… but the techs will notice that and that suggests I've touched the drivetrain of the car… at least the transmission...

While on the topic of "driving the car hard", logically, that argument would have zero basis. If it was due to that, you would see it in the rest of the drivetrain, not an isolated issue in the front diff like this one. BMW however does not give a cr*p about logic, so what I think is logical will not hold up in a warranty case, even if it is.

Someone on here posted a few years ago about vw having a "lifetime " fluid (whos lifetime?) And it definitely needing to be changed at 40k miles. Is there a tsb on the front differential or warranty on your bmw?

 

[m240.to]

Someone on here posted a few years ago about vw having a "lifetime " fluid (whos lifetime?) And it definitely needing to be changed at 40k miles. Is there a tsb on the front differential or warranty on your bmw?

Yes, the car is currently under warranty, but the front differential noise is so minor that any technician will likely dismiss it. I am very in tune with this car and noticed something was off long before I received the oil analysis reports. When I got close to the wheel arch, I heard a clack/grind that was not there before, so I know what I am hearing is not a placebo effect. Additionally, the significant wear in my front differential indicates that something must be wrong.

I haven't had the time to fully investigate the entire (most recent) fluid sample (I have it in a jar currently), but with such a short drain interval, I doubt I'll find anything visually apparent.

I have not brought the car to BMW yet because I recently took it to the track and plan to continue doing so. The car currently reads 13,000 km. I don't want BMW to perform an oil analysis, dismiss the wear as "normal" for the car's mileage, and overlook the fact that the sample they test actually has around 1,500 km on it (give or take when I decide to bring it to them), not what the cars milage is reading.

Essentially, I want enough wear to be present so that it isn't dismissed as normal wear relative to the milage.

 

[RAVL]

Either let BMW handle it under warranty or find something else to worry about.

 

[SEBZX79]

I have 3 BMWs according to a friend that's a master tech they see more front diff failures then rear. ( Not unusual at all)

On the fluid front I use redline in all my bmw diffs and only OE fluid in the transfer case. ATC45l transfer case is prone to failure around 100,000-120,000 miles.
I'm dealing with one now

 

[m240.to]

Update:

I brought it into BMW, and the road test came back inconclusive. They did a visual inspection, checking the control arms, links, etc. Once again, inconclusive, but the decided to ignore the fact that while my cars alignment is not only in spec, but perfectly within spec, the front right outer tire is completely bald while the rest have tons of tread.

Last time I checked, a bad diff can lead to different wheel speeds, causing that type of wear. I brought this up several times but of course, the dealership people lack the intellectual capacity to understand what I'm telling them.

Based on these observations, nothing could be done.

I did not mention the oil analysis, but pushed for one to be done on the diff and offered to pay all labour costs + analysis costs associated with doing so. They told me that they only do this on transmissions in the rare case BMW authorizes them to. I told them that is not true because you can open any part of the drivetrain on the BMW TIS and it will leave a warning for technicians that in the event of a warranty claim to keep a sample of the fluid for testing.

Master tech told me the only thing I can do is reach out to BMW Canada and have them give me permission to drain the fluid at the dealer, submit it off to analysis, then forward the results to BMW to see if it can be used in a warranty case. I have not contacted BMW Canada yet, but I will on Monday.