[Bims328i]

After a lot of research I am beginning to suspect my rear differential is going out or something. While changing the transmission fluid a few weeks ago I did the differential fluid as well. Noticed a surprising amount of metal flakes in the fluid, wasn't entirely sure what to make of it as I put a magnet down and poured the fluid over it in which I didn't see so many flakes.

Well fast forward to this weekend I am browsing some things and find something talking about all my symptoms relating to a bad differential (bearing and/or seals going out)

Mainly, I hear two different tones under acceleration and deceleration and nothing when hovering the throttle so there is no load. On top of this the evidence of metal flakes in the fluid. Right after I popped the fill plug you could see flakes pouring out along with the fluid.

Has anyone rebuilt a differential on their E90 328i before? New diff is about $2k while I don't think buying a random one off ebay would even be a wise decision. How could you trust it would last?

Is it possible to get a rebuild kit and fix it yourself without a bunch of specialty tools? I know bearing carriers can be a pain to remove on some.

[whyzee125]

I would trust a used one over a rebuilt one unless it was by a few certain shops. Almost nobody sets them up as well as they are from the factory. They don't commonly fail, so IMO get a used one or use this opportunity to step up to an LSD

[Bims328i]

That's surprising to hear honestly. This one has 98k miles on it though I did find one of the wheels were bent so perhaps whatever led to that might have caused some damage to the differential leading to premature failure.

I've read the E90s have some issues with differential failure. How is the process to change over to an LSD? I know what they are, but I have not looked into swapping one or setting up on an E90 in the least bit.

Still curious though, is it possible to rebuild one yourself without a press or special tools?

Thanks for your advice!

[whyzee125]

Originally Posted by Bims328i

That's surprising to hear honestly. This one has 98k miles on it though I did find one of the wheels were bent so perhaps whatever led to that might have caused some damage to the differential leading to premature failure.

I've read the E90s have some issues with differential failure. How is the process to change over to an LSD? I know what they are, but I have not looked into swapping one or setting up on an E90 in the least bit.

Still curious though, is it possible to rebuild one yourself without a press or special tools?

Thanks for your advice!

I think it's possible without special tools but you need shims, bearings, etc. that are hard to get and require a lot of skill to set up perfectly. There are a few youtube videos, one of which was doing a DIY install of an LSD.

I'm fairly mechanically inclined--I've installed an engine, a trans, done a few clutches myself, and would have no interest in trying to rebuild my diff. I don't trust myself to get it perfect.

If you were going to go the LSD route I would get one that's already setup from Mfactory, Quaife, etc. but obviously your choice. There are a number of options on how to repair it.

[Bims328i]

Really appreciate the info! I see what you're saying. From what I can tell the E90 diffs have snap rings that hold the output bearings in which are also shims that set the backlash? They don't look too difficult to remove. Input shaft is likely the diffcult part to get right.

I just looked into those two companies, and it appears you'd still have to install the LSD part yourself. They don't provide any full assemblies I assume. Not much resource for differentials on N51 328i unfortunately.

Rebuild kit or LKQ replacement, have to make sure it is the right assembly or components which can be tricky for sure.

Both of those sites are quite difficult to navigate, though an upgrade to LSD would be nice honestly. I don't know how to even find the one I would need.

Probably would help to find a reference number on my diff if there is one.

I have an 08' 328i N51 E90 with GM AT transmission.

[e90yyc]

OP: From what I recall, diff failures were more common with the units used in some European models. Fortunately the diffs we got with models sold here in NA didn’t have this problem.

As whyzee125 said, much easier to buy a used unit. Sure it can be rebuilt, but to do a proper job you kind of do need special tools—or at least something more than just your typical shadetree mechanic setup. In addition to sourcing a rebuild kit, you’d need a press and properly-sized adapters for the job.

Check out this video for an idea of what’s involved. (Rebuild of one of the European units.)

[Bims328i]

Thanks for the help! I was actually watching that haha. You can tell that guy is doing the job right / done a few of them before.

The press, tooling and torque resistance tool along with an impact wrench are all critical to do the rebuild properly for sure.

Any tips on how I can figure out exactly what diff I have in this model? I believe the sticker is on the top of the assembly. Any indicators you could gather by crawling under the car?

AT and MTs diffs on these are different lengths, correct?

[NZE90]

Originally Posted by Bims328i

Thanks for the help! I was actually watching that haha. You can tell that guy is doing the job right / done a few of them before.

The press, tooling and torque resistance tool along with an impact wrench are all critical to do the rebuild properly for sure.

Any tips on how I can figure out exactly what diff I have in this model? I believe the sticker is on the top of the assembly. Any indicators you could gather by crawling under the car?

AT and MTs diffs on these are different lengths, correct?

If you look your car up on realoem you can find out what diff it has and what ratio it is. Failures are pretty uncommon in the 325, 328 or 330. It's the small case diff that causes all the issues, but they were only fitted to the 4 cylinder models and the 323i.

I think the 328i has a type 188 (188mm crown wheel gear) diff and 3.73 ratio if it's an auto or 3.23 if it'sa manual. Best to check that though.

[Bims328i]

Big thanks for that NZE90, wasn't aware.

Using the serial reference method, I came up with what I believe is the 3.73 there (3,73).

That really helps.

[e90yyc]

You got it! You’d have the 3.73.

The xDrive folks got the 3.38 with manual and 3.91 with auto.

[jsunma]

Well, to just inject something between "new one" and "some random diff from eBay", I do think that there's much to be had between $2300 and $200. You need to get familiar with salvage yards in your area and the used parts market in general. A decent used diff should cost around $300 and it's really quite simple to install.

[Bims328i]

Originally Posted by jsunma

Well, to just inject something between "new one" and "some random diff from eBay", I do think that there's much to be had between $2300 and $200. You need to get familiar with salvage yards in your area and the used parts market in general. A decent used diff should cost around $300 and it's really quite simple to install.

I have sourced a few already and you're entirely right though what are your thoughts on picking up one that is out of a wrecked car? Specifically, say the car smacked into something while in drive, couldn't that have potentially damaged areas across the entire drivetrain?

Would be smarter to source one from a vehicle that was not involved in an accident in my opinion.

[jsunma]

Originally Posted by Bims328i

I have sourced a few already and you're entirely right though what are your thoughts on picking up one that is out of a wrecked car? Specifically, say the car smacked into something while in drive, couldn't that have potentially damaged areas across the entire drivetrain?

Would be smarter to source one from a vehicle that was not involved in an accident in my opinion.

Well, this is fodder for much comment. Hopefully others will add to the conversation.

I'm not sure what an accident would do to the differential unless it were a catastrophic front and rear crash. But, whatever. There are lots of cars wrecked from side and corner damage..plus for cars the age of yours and mine, they're just in the yard because of engine, transmission, "it's just too old", issues.

[Bims328i]

Same here, I really have no idea but rather a suspicion that certain accidents might affect or damage other components in the vehicle. Mine has no accidents reported but I know it had some sort of front end damage as a few parts were broken, missing.

Specifically, I used to have a leak on the driver's side front door which would get droplets on it after heavy rains, sometimes it would puddle up on the floor mat. I discovered it was the vapor guard/seal between the door card/panel and the door frame. I cleaned the foam vapor seal and re-beaded with fresh butyl tape but while I was looking inside the door, you could see some of those "hot-spots" from the little nails they weld on the body to pull out dents.

Someone had been in the door and comprised a lower portion of the seal. I also discovered the rear drivers side wheel was bent which was replaced a while ago. I brought it in to get the TPMS sensor replaced and the guy was like "uh, your wheel is bent pretty bad" to which he showed me while it was on the balancer and only hand spun it.

So given that some say the differentials are pretty solid and others saying they have issues I'm not entirely sure but mine only has 98k on it now. Never drove hard myself, car was in good shape when I bought it. With what I know now I'm thinking whatever happened to the car might have affected the differential.

For a donor car I'm suspecting with front-end collisions there is a good chance the car was in drive and I mean, a sudden impact or stop while the car was in drive would possibly cause some unnoticeable damage to it. Just my opinion though. If that's not the case, it's good news because I would rather spend $300-$500 than the $2.4k obviously.

Thanks for all your help!

[whyzee125]

I know at least Mfactory offers the whole diff unit (or did at one point. I have one in my car). It was like $1,200 but their pricing has varied a lot. I think getting one out of a local yard esp from a front end hit is a good move. Or a part out on CL or marketplace. IMO diff failures are not common on these cars. If you search it you'll find some failures here and there but for the most part they go 200k+ even with no fluid changes.

[Efthreeoh]

Toms Foreign Auto Parts.

[mattanderson]

Originally Posted by whyzee125

I know at least Mfactory offers the whole diff unit (or did at one point. I have one in my car). It was like $1,200 but their pricing has varied a lot. I think getting one out of a local yard esp from a front end hit is a good move. Or a part out on CL or marketplace. IMO diff failures are not common on these cars. If you search it you'll find some failures here and there but for the most part they go 200k+ even with no fluid changes.

Unfortunately, seems that Mfactory is no longer offering that service. I contacted them a few months ago and they said it's "not a unit we currently work on" (though they still offer the LSD).

Diffsonline seems like the best option I've found for a rebuilt diff (+ LSD install), but they are not cheap.

[rbryantaz]

Originally Posted by mattanderson

Unfortunately, seems that Mfactory is no longer offering that service. I contacted them a few months ago and they said it's "not a unit we currently work on" (though they still offer the LSD).

Diffsonline seems like the best option I've found for a rebuilt diff (+ LSD install), but they are not cheap.

I would just find a good used unit.

I don't think failures are that common. The difference in the full mfactory rebuild and them installing it was just the bearings and they claimed that they rarely see a bearing failure anyway....

When I did the mfactory LSD I just bought a used diff and sent that in to limit downtime. The used diff shipped from ebay wasn't much more than shipping them my diff anyway... If it had been a bad core then mfactory would have rejected it and I would have gotten another from the seller so it made sense. I got it from ey-autoparts on ebay who I have dealt with many times and had very resonable costs. I think it was $125 shipped or something really cheap like that at the time for a 188 auto bolted diff...

If you want to spend a bit more for a known good unit I still have my original clean 80k diff from my 335 auto that I need to sell but it might not be the right gear ratio for you. I would rather put it in a corner than sell for $125 though.

-Rich

[Bims328i]

Thanks for the info my guys! While I feel a bit silly saying it, I can't put my own tires on.

After doing some other needed maintenance and changing the oil I noticed I needed a front tire bad, fast forward and I am paying for four new tires, balance and alignment to be safe.

I literally have the akibono zimmerman rotor / pad set for the rear and was waiting for the sensor to go off to replace them.

The shop told me they noticed the passenger rear pad is metal to metal on the rotor so maybee that is what the sound is from.

I have to wait until this weekend to get to it. I told them that's good news haha. Going to replace the pads and rotors and see how it sounds then.

One of the pads must have gotten stuck or something. Sensor is on the opposite side.

Thanks again for all your help!

[Bims328i]

To update, I serviced the rear brakes while flushing the system this Friday and unfortunately, the noise is still present.

The rear pads were not down to metal while the CBS system reported some 33% availability, there were also no "gouges" in the rotors like the shop said.

Why I really do not like taking my car anywhere. So much rushed, careless work ethic in so many shops, and many try over charge you.

Pretty much all of the time I do my own repairs it will be solid for a long time. Should have bought the tires myself.

I had a friend ride along recently and they were saying it sounds like the sound is coming from dead center in the rear.

When putting the car on stands I did notice there is some sort of leak on the differential. I didn't snap any pics as I was super busy, but it could be the input shaft bearing as the saturation of oil looks to come from the front of the diff.

[Bims328i]

Managed to find a replacement differential which I now have in my possession. I've been checking a lot of resources for the removal and installation. Picked up a set of new bushings & bolts for diff along with the tool to pull and install them.

Now I was sitting here thinking I'm mostly ready to tackle the job this weekend and while perusing some more info I come to learn the drive axle and drive shaft bolts are possibly torque-to-yield? Meaning I should have picked up a full set of replacement bolts. Anyone have additional info or opinions on this?

From everything I've read until today, there were no clear indications that these bolts need to be replaced. Is this only for M type 3-series or something?

Thanks again!

[Efthreeoh]

Originally Posted by Bims328i

Managed to find a replacement differential which I now have in my possession. I've been checking a lot of resources for the removal and installation. Picked up a set of new bushings & bolts for diff along with the tool to pull and install them.

Now I was sitting here thinking I'm mostly ready to tackle the job this weekend and while perusing some more info I come to learn the drive axle and drive shaft bolts are possibly torque-to-yield? Meaning I should have picked up a full set of replacement bolts. Anyone have additional info or opinions on this?

From everything I've read until today, there were no clear indications that these bolts need to be replaced. Is this only for M type 3-series or something?

Thanks again!

Just reuse the bolts, no need to replace them.