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      02-15-2018, 01:25 PM   #1
Differentiall
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e90 330i 6MT to auto 328i differential swap

hey guys. i have an e90 330i 6mt and i happened to get a 328i auto differential from a buddy for free. would it be a direct p&p? tried looking it up here but couldn’t find an exact answer. thanks for your help!

Last edited by Differentiall; 02-15-2018 at 01:36 PM.
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      02-15-2018, 02:01 PM   #2
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You must not have looked very hard, lol. Yes, it will work.. as long as they're both RWD models.

EDIT: Nope, looks like it is not a direct swap due to different input shaft bolt pattern.
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      02-15-2018, 02:05 PM   #3
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why would it matter if it was RWD? the rear diffs are the same.
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      02-15-2018, 02:19 PM   #4
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Quote:
Originally Posted by atmosphericM View Post
You must not have looked very hard, lol. Yes, it will work.. as long as they're both RWD models.
apparently haha. I saw that it was direct for the 328i 6mt and 328i auto diff but wasn't sure about the 328i auto diff into the 330i. both are rwd
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      02-15-2018, 02:43 PM   #5
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Quote:
Originally Posted by hassmaschine View Post
why would it matter if it was RWD? the rear diffs are the same.
Is this true, you're sure? When I was browsing a while back I thought I noticed that the XI's input shaft had a different bolt pattern. I also could have sworn I read that the XI's weren't compatible...

If they are, that means we can get a 3.91 FD because that's what I'm seeing for the XI models (at least for the 328xi).

EDIT: I hate to disagree but I just re-checked eBay and I'm seeing a 3 bolt pattern for the 328 XI-AWD models whereas the 328i RWD models have an 8 (4) bolt pattern on the input shaft to the differential pumpkin. So I'm going to say again that I don't think the AWD carrier would work (sure you might be able to change the input shaft but why bother with all of the extra work?).

Last edited by atmosphericM; 02-16-2018 at 12:16 PM.
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      02-15-2018, 02:43 PM   #6
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Quote:
Originally Posted by Differentiall View Post
apparently haha. I saw that it was direct for the 328i 6mt and 328i auto diff but wasn't sure about the 328i auto diff into the 330i. both are rwd
AFAIK, the only difference between the 328i and 330i AT RWD Differential is the FD: 3.64 for the 330i AT and 3.73 for the 328i AT.

EDIT: This is actually incorrect! It appears that the 330i/330xi (and 328xi) uses the 3 bolt pattern input shaft whereas the 328i (rwd) unit uses the 4/8 bolt pattern input shaft.

Last edited by atmosphericM; 02-16-2018 at 12:18 PM.
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      02-15-2018, 03:04 PM   #7
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Quote:
Originally Posted by atmosphericM View Post
Is this true, you're sure? When I was browsing a while back I thought I noticed that the XI's input shaft had a different bolt pattern. I also could have sworn I read that the XI's weren't compatible...

If they are, that means we can get a 3.91 FD because that's what I'm seeing for the XI models.

EDIT: I hate to disagree but I just re-checked eBay and I'm seeing a 3 bolt pattern for the XI-AWD models whereas the RWD models have an 8 (4) bolt pattern on the input shaft to the differential pumpkin. So I'm going to say again that I don't think the AWD carrier would work (sure you might be able to change the input shaft but why bother with all of the extra work?).
I'm was going off part numbers - 330i and 330xi both have the exact same diff at least.

it's not easy to tell because the gear ratios are usually different between RWD and AWD models.

All the flex disks in the rear are the same:
http://www.realoem.com/bmw/enUS/part...&q=26117527392

I have to believe the input shaft isn't different or they couldn't share flex disks.
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      02-15-2018, 03:12 PM   #8
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Some of the diffs have different pinion flanges. I noticed this when I was shopping for my diff.

You can swap the pinion flanges from one to another though.
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      02-15-2018, 03:41 PM   #9
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Quote:
Originally Posted by atmosphericM View Post
AFAIK, the only difference between the 328i and 330i AT RWD Differential is the FD: 3.64 for the 330i AT and 3.73 for the 328i AT.
i was thinking the same exact thing. but i always want to double check to make sure on these types of things. i appreciate the feedback!
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      02-16-2018, 12:05 PM   #10
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Well I'm glad you brought this up, because actually I think I was totally wrong (I blame the other thread here ).

Quote:
Originally Posted by hassmaschine View Post
I'm was going off part numbers - 330i and 330xi both have the exact same diff at least.

it's not easy to tell because the gear ratios are usually different between RWD and AWD models.

All the flex disks in the rear are the same:
http://www.realoem.com/bmw/enUS/part...&q=26117527392

I have to believe the input shaft isn't different or they couldn't share flex disks.
Interesting. You are totally right. I'm really glad you brought this up. In the other thread going, the consensus seemed that one could use 330/325 units interchangeably with 328 units, but after digging through the link you just posted, it looks like the 330i flex disc is the same as that of the 330xi. And the more I looked around... it appears that the 330i, 330xi, 325xi all share the same 3 bolt input shaft (looks like the 325i RWD unit uses the 4/8 bolt pattern found on the 328i RWD.. just to make things more confusing). I didn't see anything about 328's for that part number (except for XI's and EURO models), so I would now say that the 328i diff would not be a direct swap into the 330 platform, as the 328i unit has the 4/8 bolt pattern input shaft vs. the 3 bolt pattern found on the XI's (all models?) and 330i. Thanks BMW... thanks. lol they really don't make it easy for us do they?

As biginboca said, you could probably swap the input shafts; however I've never done that personally so I don't know how involved it would be. Not super hard, I'm sure.. maybe someone here can chime in. I do know that swapping the shafts usually involves new seals.. all of which can be kind of a pain at times I've heard due to possibility of leaks, etc.

The good news here is that you 330i guys now seem to have an even more aggressive option for swapping final drives via changing the entire pumpkin - the 330i auto RWD diff (3.64), as well as the 328xi auto XI diff which is 3.91 (however I cannot commit to saying 100% for sure that the 328xi unit works, as perhaps there is another difference between the 325/330 and 328 platform.. hopefully someone with a 330i can chime in here)! That'd be a jump, heh. I'd also imagine the 330xi auto XI diff would be a direct swap; I'm not sure what the final drive on that unit is though.

I suppose this also means that one could rock the 3.91 328XI rear pumpkin in a 328i, however you would need to swap the input shaft.

I wonder if there are any other differences internally, regarding the actual differential itself. (Probably not, but the XI diff would not need to handle as much power as the RWD diff, so who knows?)

Disclaimer: This is all based upon internet reading though, just to be clear. What we really need is someone who has personally done a swap between the 330/325 platform and the 328 platform to confirm these findings.
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Last edited by atmosphericM; 02-16-2018 at 01:27 PM.
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      02-16-2018, 12:29 PM   #11
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      02-16-2018, 01:12 PM   #12
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Quote:
Originally Posted by atmosphericM View Post
Well I'm glad you brought this up, because actually I think I was totally wrong (I blame the other thread here ).



Interesting. You are totally right. I'm really glad you brought this up. In the other thread going, the consensus seemed that one could use 330/325 units interchangeably with 328 units, but after digging through the link you just posted, it looks like the 330i flex disc is the same as that of the 330xi. And the more I looked around... it appears that the 330i, 330xi, 325xi (looks like the 325i RWD unit uses the 4/8 bolt pattern found on the 328i RWD.. just to make things more confusing) all share the same 3 bolt input shaft. I didn't see anything about 328's for that part number (except for XI's and EURO models), so I would now say that the 328i diff would not be a direct swap into the 330 platform, as the 328i unit has the 4/8 bolt pattern input shaft vs. the 3 bolt pattern found on the XI's (all models?) and 330i. Thanks BMW... thanks. lol they really don't make it easy for us do they?

As biginboca said, you could probably swap the input shafts; however I've never done that personally so I don't know how involved it would be. Not super hard, I'm sure.. maybe someone here can chime in. I do know that swapping the shafts usually involves new seals.. all of which can be kind of a pain at times I've heard due to possibility of leaks, etc.

The good news here is that you 330i guys now seem to have an even more aggressive option for swapping final drives via changing the entire pumpkin - the 330i auto RWD diff (3.64), as well as the 328xi auto XI diff which is 3.91 (however I cannot commit to saying 100% for sure that the 328xi unit works, as perhaps there is another difference between the 325/330 and 328 platform.. hopefully someone with a 330i can chime in here)! That'd be a jump, heh. I'd also imagine the 330xi auto XI diff would be a direct swap; I'm not sure what the final drive on that unit is though.

I suppose this also means that one could rock the 3.91 328XI rear pumpkin in a 328i, however you would need to swap the input shaft.

I wonder if there are any other differences internally, regarding the actual differential itself. (Probably not, but the XI diff would not need to handle as much power as the RWD diff, so who knows?)

Disclaimer: This is all based upon internet reading though, just to be clear. What we really need is someone who has personally done a swap between the 330/325 platform and the 328 platform to confirm these findings.
Yeah it looks like only the RWD 328s have the different bolt pattern.

For swapping the input, you would need to mark the position of the nut, count the number of turns when you remove it, put in a new crush bearing, then tighten it back down to the exact same spot.. Otherwise the pinion bearing lash won't be right and it will fail. It's not impossible, but for many people they probably shouldn't try it themselves unless they know the consequences..
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      02-16-2018, 03:22 PM   #13
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Quote:
Originally Posted by hassmaschine View Post
Yeah it looks like only the RWD 328s have the different bolt pattern.

For swapping the input, you would need to mark the position of the nut, count the number of turns when you remove it, put in a new crush bearing, then tighten it back down to the exact same spot.. Otherwise the pinion bearing lash won't be right and it will fail. It's not impossible, but for many people they probably shouldn't try it themselves unless they know the consequences..
In my experience when swapping pinions on diffs you need to use a new crush sleeve and check backlash as you torque the pinion nut. You continue torquing in small increments (5ft/lbs or so) until you get the right backlash. This is a science and the longevity and performance of your diff depends on accuracy. That is the best and correct way.

But...

I’ve also done it myself the shortcut way Hass described a few times and never had a problem. I agree with the way he described above but with a small exception...

For the shortcut way I was taught and have always done it like this. I marked the nut position and REUSED the same crush sleeve. If you use a new crush sleeve you need to do the other procedure I described above and torque to spec measuring the backlash. Using a new crushsleeve requires starting over with setting the backlash. That’s how I was taught anyway.
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