For those who don't know, there are two sizes of ring and pinion for the E9X(and others), 188mm and 215mm. A later post explains the differences between models, but most people with an auto have the smaller, 188mm which I'm told also has thinner axles. Currently I have the 188mm, but I'd like to convert while I am doing my LSD so I bought a 215mm auto pumpkin out of a 2006 production auto 335i. After asking, Jesse(@Darklabs ) informed me that the 188mm axles and driveshaft will fit in the 215mm differential, so this may be a direct swap.
The reason for doing this is the potential strength benefit as well as being able to add a differential cover with fins and a drain plug, which mine does not have.
As far as differential cover options, excluding the $800 cover made by VAC, there is the M3 diff cover p/n: 33112283010 which has no fill/drain hole and is quite pricey. And my current favorite, the E63 650i finned cover which fits the big diff. Keep in mind, if you're auto, you'll need to either have the 215mm differential, convert from the 188mm diff like I'm trying to do, or see if the 188mm finned diff cover mentioned at the bottom of this post will fit. Please keep in mind, I don't know how any of these covers work with diff lock down kits. Here is a picture from @PC Racing
This cover has a 1.25" lower clearance and requires a spacer and longer bolt to prevent it from being pulled out of the subframe when tightned, since it is not as thick as the stock cover. You may also need to trim a few fins so the exhaust does not interfere, just depending on what exhaust you have. @PC Racing is making me a 15.5mm spacer which I'll be testing and see if it works.
What you'll need:
650i Cover: 33117519661
M14X1,5X130 Grade 8.8 Bolt: 07119914854 (Or the recommended grade 10.9 Bellmetric Bolt BH 14 X 1.5 X 130)
M10x25 hex bolt: 33117521292
And a spacer that needs machined: @PC Racing can make them, see pics of it Here
Here are some comments from Pig Farmer on making the spacer:
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As for the auto guys with the 188mm diff, there is also another part number: 33117516280
This apparently fits the 188mm 128i with a 15mm spacer, but I don't know if there is any compatibility with the '35i small 188mm diff.
This photo is from Bimmer-Bob
The reason for doing this is the potential strength benefit as well as being able to add a differential cover with fins and a drain plug, which mine does not have.
As far as differential cover options, excluding the $800 cover made by VAC, there is the M3 diff cover p/n: 33112283010 which has no fill/drain hole and is quite pricey. And my current favorite, the E63 650i finned cover which fits the big diff. Keep in mind, if you're auto, you'll need to either have the 215mm differential, convert from the 188mm diff like I'm trying to do, or see if the 188mm finned diff cover mentioned at the bottom of this post will fit. Please keep in mind, I don't know how any of these covers work with diff lock down kits. Here is a picture from @PC Racing
This cover has a 1.25" lower clearance and requires a spacer and longer bolt to prevent it from being pulled out of the subframe when tightned, since it is not as thick as the stock cover. You may also need to trim a few fins so the exhaust does not interfere, just depending on what exhaust you have. @PC Racing is making me a 15.5mm spacer which I'll be testing and see if it works.
What you'll need:
650i Cover: 33117519661
M14X1,5X130 Grade 8.8 Bolt: 07119914854 (Or the recommended grade 10.9 Bellmetric Bolt BH 14 X 1.5 X 130)
M10x25 hex bolt: 33117521292
And a spacer that needs machined: @PC Racing can make them, see pics of it Here
Here are some comments from Pig Farmer on making the spacer:
---------------
As for the auto guys with the 188mm diff, there is also another part number: 33117516280
This apparently fits the 188mm 128i with a 15mm spacer, but I don't know if there is any compatibility with the '35i small 188mm diff.
This photo is from Bimmer-Bob
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