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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Complete M3 subframe swap



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      11-30-2012, 10:44 AM   #23
Nigelo
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Wonder what happened? A few folks have managed it so far.
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      12-05-2012, 06:40 PM   #24
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I guess I'm just wondering whats driving you to want the 335 hubs if you have everything from the m3 subframe? Otherwise, you haven't bolted the subframe up yet? I've got the driveshaft on the way but I'm also wondering why you've decided to join the shaft at the gearbox end, just looking for insight and figuring out what people will need pictures of...

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      12-05-2012, 06:49 PM   #25
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Hi!

Reason for the 335i hubs is to keep the 335i brakes. Otherwise you will have larger brakes on the rear than the front as well as them being designed for the M3 brake cylinder which is bigger. You could keep the M3 rear hubs but you'd need either M3 front brakes+hubs or a balanced front bbk.

As for the main driveshaft / propshaft, you do have a choice. Either 335i shaft from box to after the centre bearing, joined to an M3 diff end, OR an 335i box end joined to M3 shaft before the centre bearing. It's really just to ensure the length from box or diff is correct to the centre bearing mounting point, and that only one cut and join is needed.
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      12-05-2012, 10:16 PM   #26
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ok, I see. My front bbk is already on the way. I had just figured the easiest way to keep the center bearing in the same place was to keep the 335 front half. Guess I'll be able to tell which half would make more sense once its all bolted up and I have both shafts there. Now I just have to figure out if my offsets will still work for fitment...
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      12-25-2012, 12:19 PM   #27
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Definitely see it now, back half of the M3 is correct length for dct diff and lines up with the bolt holes in the frame. M3 shaft needs about 2cm cut off and 105/12mm guibo instead of 110mm. Finding somebody in Florida to balance it is also turning out to be tricky. Have an extra M3 shaft if anybody needs one...
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      01-02-2013, 02:46 PM   #28
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Quote:
Originally Posted by skyguy View Post
Definitely see it now, back half of the M3 is correct length for dct diff and lines up with the bolt holes in the frame. M3 shaft needs about 2cm cut off and 105/12mm guibo instead of 110mm. Finding somebody in Florida to balance it is also turning out to be tricky. Have an extra M3 shaft if anybody needs one...
So are you saying that rear part of M3 DCT drive shaft fits perfectly from diff to center bearing? And just front part of the drive shaft should be shortened welded and balanced?

Did any of you who did this... By how much and which part you had to shorten driveshaft? (Was it from DCT drive shaft?)

Last edited by RimasRS; 01-02-2013 at 03:01 PM.
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      01-11-2013, 10:21 AM   #29
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The spacing from the m3 diff to the center bearing frame mounting holes is correct for the appropriate m3 shaft. The spacing from trans to center bearing is correct for the 335 shaft. You could do it either way, put the m3 diff end on the 335 shaft or put the 335 trans end on the m3 shaft. Either way it needs to be shorter. For the M3 dct shaft its about 2 cm shorter. Once you see the 2 shafts side by side you'll probably choose to use the beefier m3 shaft.

-Sky
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      01-12-2013, 01:11 PM   #30
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Great info there skyguy!

How close is it to 2cm shorter - if you can get it down a little more accurate thatd be amazing - means driveshafts could be made up without having to measure up with everything preinstalled and then wait for the driveshaft company.
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      01-20-2013, 11:55 AM   #31
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We're still trying to decide the best way to measure it, measure twice cut once I guess? Wish Georgesmooth or Idnan would just post their driveshaft lengths, not like I'm going to blame or hold anyone liable if it doesn't fit correctly on the first attempt.
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      01-20-2013, 05:18 PM   #32
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Hi Guys,

Well I'm planning the same thing although I haven't started ripping things apart yet I am just getting my facts straight before I start

So one of the questions some people may have is WHY? and WHAT ABOUT A QUAIFE?

Well in short this route is cheaper for below reasons (asuming your getting a used M3 subframe)

If you install a Quaife you will have a great LSD but everything else is 335i. If you are running stock power then IMHO this works great

BUT most of us are trying to break the sound barrier RIGHT!

M3 complete subframe gives you

1, Amazing LSD
2, M3 bushing all over the rear
3, Bigger Stronger Drive Axles for the bigger power
4, Bigger Stronger Prop Shaft for the bigger power
5, Better sway bar or ARB as we call them over here
6, Rear breaks get upgraded by default if you keep them on

Add this up and for the same price or less the Quaife isn't such a great deal

So HOW do we do this and remove all the smoke from this subject.

Well if I could I would create a KIT and sell it to the 335i fraternity who want to mate a complete M3 Subframe transplant. HE WHO DARES WINS

What would the kit have (Oh! and pleae add to this idea)
Part 1, Prop conversion kit which contains the front prop shaft which mates to the M3 rear prop shaft and MISC parts etc..
Part 2, Optional Front BBK to compliment the M3 bigger rear brakes (the 3rd part is no longer required if you go with this option)
Part 3, Adjustable camber arm? so we can use our 335i hubs, disks and calipers

Some Facts that I have picked up so far (Thanks to Idnan, what a gentleman!)
DIFF RATIOS
M3 7DCT Diff FD 3.15
M3 6MT Diff FD 3.85
335i 6MT Diff FD 3.08
335i 6AT Diff FD 3.46

(FD) means Final Drive for those googlers

So when looking at this data, 335i guys with 6AT trans have there pick of both M3 diffs as they are 0.30 between the two ratio's. BUT IMHO 6MT guys should use the 7DCT M3 diff or else the final drive will be way to short and 1st gear will be unusable

I've opted for the 7DCT Diff as I feel with my power mods, 1st gear is too torqued and I end up starting with 2nd. With this in mind the drop from 3.46 to 3.15 will give 1st gear slightly longer gearing but not as long as the current 2nd gear. Once the 6AT is rolling it makes no odds as the Torque converter will sort things out.
Maybe it might improve MPG on highway cruises

So another important factor is the Prop Shaft modification which is playing on everyones mind.

Which M3 prop to use and how to measure and cut weild it

I have noted that the M3 has two sized props. I believe 7DCT diffs carry the longest prop so maybe for the sake of a cm here and there get the longer one

How to measue it? Well I'm no expert but my theory is to offer it up to the car decide which end to cut (I'm siding with the Trans end) and cut as close to the end as possible. You will then need to use your 335 prop as a donnor to mate this to the 335 tranny

I would measure with some form of solid wire which has zero stretch and clamp it to the diff and then pull it over to the tranny. I would also cut less which may mean more cutting but also means you have options if you cock it up.

Weilding it? well obviously get a professional prop shaft company to weild and balance the prop but until meanwhile I would tack the cuts together like a prototype so you can install it to the car and turn the wheels and see if your prop is fitting in all the right places.

Well good luck to all attempting this and once my project is underway I will detail my steps and offer up real measurements for those of you interested with pictures and all

Thanks
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      01-22-2013, 11:53 AM   #33
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Update

I have sourced two prop shafts and after my install may have a complete M3 prop for sale.

Please express your interests
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