[Giggler]

I have just recently noticed a rear diff fluid leak on my car also. Going to schedule it for service... is there a TSB out for this yet? I would be content to wait a few more months for BMW to come up with a procedure.

[TheDudeMan]

This happens from time to time. When I picked up my f30, I started smelling burning in my garage at 8 miles lol. Next morning, small drips under my car. Turned out to be an axle seal damaged during assembly.

With that said this not an issues I would attempt to figure out on your own. Best thing to do is leave it, let it drip as evidenced and bring it in for service.

[shawntech]

Mines doing it again unsure why, sigh

[danahmedG20]

Originally Posted by BMW_Midlo_Man

So let's start this by saying - My M340i has been AMAZING to own thus far. It's gorgeous. It's beyond-my-expectations powerful. The speed and power has easily been underrated by my estimations. For me, it's the perfect blend of automotive prowess, driving dynamics, and modern technology & features.

But here comes my first mechanical gremlin... I noticed multiple drops of oil (equating to ~2 tablespoons of somewhat blackened oil in my garage. No smell to it, doesn't smell burned. But being that I only park this car in one specific orientation in my garage, I know the oil is coming from the rear axle area of the car along the centerline, and the most-likely candidate would be my rear-diff seal(s).

Car is only 7 months into ownership, with ~6,000 miles on it.

Cleaned up the drips, I've kept checking after parking multiple times and I have not been able to confirm whether any new drops have formed.

I'll be notifying BMW and taking it in for service, but I'm a bit uncertain as to whether or not they'll end up flashing the ECU (as per the open emissions recall) during my service visit, and I am still running the pre-July ECU (that, from what I gather has left me with a lot of unexpected power).

• Is anyone else seeing rear-diff leaks on the new M340i?
• Anyone have any other thoughts as to what it could be if not a rear-diff seal leak?
• Has anyone been forced to have the ECU flashed per the recall while having other service work performed? If so, how has it affected your driving experience?

Same thing happened to be after I was pushing the car pretty hard around 10k miles.

A couple of drops but nothing too serious. I took it to BMW and they cleaned it up and informed me that it was overfilled from the factory.

Haven't had the issue come back up and I'm at 17k miles nows

[samoedin]

Same problem here with only 1200 miles

[MBM340]

Originally Posted by samoedin

Same problem here with only 1200 miles

Wow, that is more than a few drops...

[SemtexGT]

I noticed my diff leaked about 3 drops this evening, exactly how it was described here, after a hard drive. First time I see it. I'm gonna call the dealership and see how that goes.

[SemtexGT]

Off to a great start to the day

[SemtexGT]

Alright, hope this thread isn't dead. Did anyone solve this problem in the end?

Mine is still leaking after rechanging the fluid at the dealership. They said it's from the breather hole at the top of the differential and that I shouldn't worry about it because it is minimal and it can't cause damage to the differential. They even gave me a report from BMW about the problem, so it seems like they are aware of it. I'll post it here so you guys can read it as well.

Let me know if anybody still has this problem and how they are coping with it.
I did 20k km, so like 14k miles I think? Car didn't skip a beat, but it still stresses me out a bit thinking about it.

[tarrant64]

For what it's worth, coming from a Focus RS it also had the rear diff leaking issue.
Kept an eye on it and it never got worse than a very minor leak - It never resulted in any problems, but it was something that ultimately was covered under warranty regardless so I tried not to stress about it either.

[baturbo]

Originally Posted by SemtexGT

Alright, hope this thread isn't dead. Did anyone solve this problem in the end?

Mine is still leaking after rechanging the fluid at the dealership. They said it's from the breather hole at the top of the differential and that I shouldn't worry about it because it is minimal and it can't cause damage to the differential. They even gave me a report from BMW about the problem, so it seems like they are aware of it. I'll post it here so you guys can read it as well.

Let me know if anybody still has this problem and how they are coping with it.
I did 20k km, so like 14k miles I think? Car didn't skip a beat, but it still stresses me out a bit thinking about it.

My dealer is trying to say that this issue is caused by my tune. A very reputable mechanic in my area said this is not the case as it is a known issue. Is there a TSB for this one?

[xnick101]

I just got my car back from the dealer for the diff leaking. They sprayed the entire thing down with tracing powder. Told me to bring it back in 250 miles. So I did. They found that the drain plug was leaking so they topped off the fluid and replaced the drain plug. They put tracing powder on it again. Been 2 days and no leak yet but I will monitor it.

[xnick101]

Originally Posted by xnick101

I just got my car back from the dealer for the diff leaking. They sprayed the entire thing down with tracing powder. Told me to bring it back in 250 miles. So I did. They found that the drain plug was leaking so they topped off the fluid and replaced the drain plug. They put tracing powder on it again. Been 2 days and no leak yet but I will monitor it.

Update: I see fresh fluid on the subframe, however not on the diff anymore. Sent pictures to the service advisor and he said to bring the car back again tomorrow.

[baturbo]

Originally Posted by xnick101

Update: I see fresh fluid on the subframe, however not on the diff anymore. Sent pictures to the service advisor and he said to bring the car back again tomorrow.

What did they say?

[naps340]

This is a very common problem, it isn't a major problem. The problem is due to the diff cover being defective under heat and cooling it sweats and causes it to leak.

[xnick101]

Originally Posted by baturbo

What did they say?

They couldn't get the car in and I had to go on a business trip this week. So will update shortly after I get back.

[xnick101]

I took the car back to the dealer last Monday. They said the diff is dry after replacing the drain plug. So that fixed some of the leak. But it's still leaking since there's fluid on my garage floor and the subframe is wet. However, they can't find the source of the leak. They cleaned it off and then the tech drove it around for 50 miles (ps..thanks to the tech for beating the fuck out of it, got the car back with only 29 miles remaining, and gave it to them with just below half tank). And they said it wasn't leaking after they test drove it. So they told me to just keep driving it.

[Giggler]

I’ve had this leak for over a year and I ignored it based on this thread saying it’s a, “BMW thing”. It’s usually just a few drips here and there after hard driving, but perhaps the leak has gotten worse just recently?

So I go for regular interval service and the dealer flags it during their inspection as a warranty repair. They’ve had the car for three days waiting for a replacement part to arrive. I’ll edit this post once I get my car back and learn what part was replaced… maybe the issue was elevated to a TSB and there’s an official fix for it.

[Insane435]

I had a decent size stain on my floor from the rear diff leak. I took it to the dealer and after 3 hours, they said they wiped it clean and said its normal. A leaking diff is not normal. If it happens again, which it will, I will be taking it back until its addressed.

Sounds like some members here got there's replaced or had some of the case replaced.

[xnick101]

I've been the dealer 3 times. The oil is blowing onto the subframe from the diff's breather holes on top. They won't acknowledge the issue and says there's no leak coming from the diff itself.

[Giggler]

My service adviser notified me that the leak was coming from both the drive shaft and wheel axle connection points to the differential. This is a bit worrying to me... but hoping the fix does the job. If they're replacing a defective part for the same part, it stands to reason the part will fail again? One of the parts is labeled "repair kit", so perhaps there's a known issue and this is meant to repair it. I will be looking for fresh fluid on my garage floor in the future but will be driving her easy for a while just in case the replacement parts need time to settle in. As others have stated, I only ever notice drops on my floor after spirited driving.

Here's the bill of materials for the work performed:

3 - 83-22-2-447-362 - HYPOID AXLE BMMI
1 - 83-19-0-404-517 - LOCTITE 5970 01BCMB
1 - 33-11-7-525-064 - SCREW PLUG W BMBIMI
2 - 33-10-7-568-368 - GASKET SET D BMRRSA
1 - 33-12-7-607-158 - REPAIR KIT I BMMIRR

Links to the main mechanical parts in the BOM.
https://www.bmwpartsdeal.com/parts/b...127607158.html
https://www.bmwpartsdeal.com/parts/b...117525064.html
https://www.bmwpartsdeal.com/parts/b...107568368.html

[cyam]

Yes - have a 2020 M340i about 20,000kms on it and I have noticed some drops of oil under the rear diff. I have it scheduled for dealer to inspect/fix next week.

I am unaware of any ECU flashes/upgrades, I had the car serviced last week and they said no software upgrades were needed. Mind you I have only had the car a couple of weeks. It was due a service which was of no charge to me. They should have noticed the diff leak IMO.

Will let you know what they say after I bring it in.

Originally Posted by BMW_Midlo_Man

So let's start this by saying - My M340i has been AMAZING to own thus far. It's gorgeous. It's beyond-my-expectations powerful. The speed and power has easily been underrated by my estimations. For me, it's the perfect blend of automotive prowess, driving dynamics, and modern technology & features.

But here comes my first mechanical gremlin... I noticed multiple drops of oil (equating to ~2 tablespoons of somewhat blackened oil in my garage. No smell to it, doesn't smell burned. But being that I only park this car in one specific orientation in my garage, I know the oil is coming from the rear axle area of the car along the centerline, and the most-likely candidate would be my rear-diff seal(s).

Car is only 7 months into ownership, with ~6,000 miles on it.

Cleaned up the drips, I've kept checking after parking multiple times and I have not been able to confirm whether any new drops have formed.

I'll be notifying BMW and taking it in for service, but I'm a bit uncertain as to whether or not they'll end up flashing the ECU (as per the open emissions recall) during my service visit, and I am still running the pre-July ECU (that, from what I gather has left me with a lot of unexpected power).

• Is anyone else seeing rear-diff leaks on the new M340i?
• Anyone have any other thoughts as to what it could be if not a rear-diff seal leak?
• Has anyone been forced to have the ECU flashed per the recall while having other service work performed? If so, how has it affected your driving experience?