HELP: M3 diff

[TUN3D]

Hey guys, so I'm gearing up for a big power upgrade in the 1st quarter. I've been told that the M3 diff/rear subframe (vs. an LSD) is the best way to go.

That said, I found a bunch of old threads and mixed info on the subject. I need your help compiling a list of the bare minimum parts needed to make this happen.

Hope you can help me out.

[ilikebmxbikes]

Originally Posted by TUN3D

Hey guys, so I'm gearing up for a big power upgrade in the 1st quarter. I've been told that the M3 diff/rear subframe (vs. an LSD) is the best way to go.

That said, I found a bunch of old threads and mixed info on the subject. I need your help compiling a list of the bare minimum parts needed to make this happen.

Hope you can help me out.

It is an opportunity to upgrade more than the LSD if you go that route. I would buy used axels off of a salvage m3 and a new m3 prop shaft ( ~$660) and do the following to complete your 1m conversion and take it from being a cosmetic conversion to a cosmetic/mechanical conversion.

- complete rear m3 subframe w/ suspension w/ M3 3.15LSD ( 1M/ M3 DCT)

- adaptors to accomade non //M suspension on //m rear camber links or suspension that works on //M

- Front M3 suspension knuckles

- Front / Rear M3 brakes

- Front / Rear M3 sway bars

- 1M Driveshaft

I would also take the opportunity to put in solid rear subframe bushings.

[dcaron9999]

Originally Posted by ilikebmxbikes

It is an opportunity to upgrade more than the LSD if you go that route. I would buy used axels off of a salvage m3 and a new m3 prop shaft ( ~$660) and do the following to complete your 1m conversion and take it from being a cosmetic conversion to a cosmetic/mechanical conversion.

- complete rear m3 subframe w/ suspension w/ M3 3.15LSD ( 1M/ M3 DCT)

- adaptors to accomade non //M suspension on //m rear camber links or suspension that works on //M

- Front M3 suspension knuckles

- Front / Rear M3 brakes

- Front / Rear M3 sway bars

- 1M Driveshaft

I would also take the opportunity to put in solid rear subframe bushings.

Go big or go home ...

You are looking at a few dollars and some down time to do all this, but sounds like a nice project! Depends also if you accept getting rid of your pretty painted F/R stock Brembo calipers ... ;-)

[ilikebmxbikes]

Originally Posted by dcaron9999

Go big or go home ...

You are looking at a few dollars and some down time to do all this, but sounds like a nice project! Depends also if you accept getting rid of your pretty painted F/R stock Brembo calipers ... ;-)

It can all be done in a day. The 135i brembos are inferior to the stock m3 brakes. Everything is an upgrade.

When you consider an LSD typically costs around $2200 for a pumpkin after core, m3 suspension (front and rear) is usually in the $2k range, sway bars are ~$400 and m3 subframe bushings are ~ $900 after labor - the upgrades I suggest really do come in as a bargain if your car does not have the above items and you get the m3 parts off of a salvage.

[TUN3D]

Thanks for the quick response. I defiantly want to do the entire thing. But I also have to budget for the turbos, install and everything else that comes with that. My question is, can I do the diff first, then suspension and brakes down the road?

[TUN3D]

...or as an alternative. Get an LSD put in now...then do the whole m3 upgrade in one shot at a later point.

[TUN3D]

Found these. How's the pricing?

Subframe:
http://www.ebay.com/itm/BMW-M-COUPE-...item3a950d88b0

http://www.ebay.com/itm/BMW-E92-E93-...064ba6&vxp=mtr

Diff:
http://www.ebay.com/itm/BMW-E90-E92-...02aed6&vxp=mtr

http://www.ebay.com/itm/08-13-BMW-M3...318ceb&vxp=mtr

[aloksatoor]

Is the subframe on the 1m/m3 beefier/better than the stock 1 series one? Whats the advantage vs just putting the control arms on the stock 1 series subframe?

[TZANIDO777]

Your best bet is to look for the whole M3 rear subframe with diff, halfshafts and control arms. Do it all one shot cause you will save on the labor unless youre doing it yourself then it does not matter.

I did all these upgrades to my 1 series in September along with the M3 front control arms, AST coilovers with vorshlag camber plates, solid subframe and diff bushings and it saved alot on labor doing it all at once.

Only recommendation is to look for the sub frame with the DCT diff instead of the manual one. Ratio in the manual diff (3.85) is way too high for our cars. That is my only regret but it now gives me the opportunity to get a custom clutch lsd to swap out with any ratio, ramping, preload i like because the internals of the M3 diff are up gradable.

[ilikebmxbikes]

Originally Posted by TUN3D

Found these. How's the pricing?

Subframe:
http://www.ebay.com/itm/BMW-M-COUPE-...item3a950d88b0

http://www.ebay.com/itm/BMW-E92-E93-...064ba6&vxp=mtr

Diff:
http://www.ebay.com/itm/BMW-E90-E92-...02aed6&vxp=mtr

http://www.ebay.com/itm/08-13-BMW-M3...318ceb&vxp=mtr

Originally Posted by TZANIDO777

Your best bet is to look for the whole M3 rear subframe with diff, halfshafts and control arms. Do it all one shot cause you will save on the labor unless youre doing it yourself then it does not matter.

I did all these upgrades to my 1 series in September along with the M3 front control arms, AST coilovers with vorshlag camber plates, solid subframe and diff bushings and it saved alot on labor doing it all at once.

Only recommendation is to look for the sub frame with the DCT diff instead of the manual one. Ratio in the manual diff (3.85) is way too high for our cars. That is my only regret but it now gives me the opportunity to get a custom clutch lsd to swap out with any ratio, ramping, preload i like because the internals of the M3 diff are up gradable.

Exactly - you will want a complete m3 lsd w/ suspension components.

If you want a M3 DCT LSD (3.15) - I can get you one for $750 + ship.

[TUN3D]

ilikebmxbikes > So technically, would I be able to buy and install the M3 LSD ONLY, and do the subframe & suspensions mods later on?

[ilikebmxbikes]

Originally Posted by TUN3D

ilikebmxbikes > So technically, would I be able to buy and install the M3 LSD ONLY, and do the subframe & suspensions mods later on?

The m3 diff is not a bolt up only option. The axelshafts, propshaft etc. wont bolt in.

[TUN3D]

ilikebmxbikes > Thanks for answering my questions man. First time really looking at a subframe/LSD, etc.

Found these pics on another post. It really helped put it all into perspective. I see what you mean...

[mike082802]

Originally Posted by TZANIDO777

Your best bet is to look for the whole M3 rear subframe with diff, halfshafts and control arms. Do it all one shot cause you will save on the labor unless youre doing it yourself then it does not matter.

I did all these upgrades to my 1 series in September along with the M3 front control arms, AST coilovers with vorshlag camber plates, solid subframe and diff bushings and it saved alot on labor doing it all at once.

Only recommendation is to look for the sub frame with the DCT diff instead of the manual one. Ratio in the manual diff (3.85) is way too high for our cars. That is my only regret but it now gives me the opportunity to get a custom clutch lsd to swap out with any ratio, ramping, preload i like because the internals of the M3 diff are up gradable.

how much you think the whole rear subframe assmbly goes for through a scrap yard?

[TZANIDO777]

Originally Posted by mike082802

how much you think the whole rear subframe assmbly goes for through a scrap yard?

I found one in Texas for $3000 on eBay, I offered $2000 and they accepted the offer and I got the subframe, diff, halfshafts, control arms, rotors, calipers, wheel hub, and wheel bearings so it was not a bad deal at all.

It was on the wrecked car for 27k miles.

[TUN3D]

TZANIDO777 > That's a freakin' steel from what I'm finding. So far, I'm only finding bits and pieces. I got the subframe, LSD, Right & Left Complete Suspension Assembly (Axles, Control Arms, Spindle, Trailing Arms, etc.). I also found a complete brake set (rotor/calipers).

$0850.00 > LSD - ilikebmxbikes
$1088.94 > Rotors & Calipers
$0659.99 > R Suspension
$0849.99 > L Suspension
$0514.45 > Sub Frame
=========================
$3963.37 > Total

This doesn't include the shocks/springs or front suspension knuckles, etc.

[TUN3D]

Any of you guys have good leads on salvage yards, websites, etc.

[Kgolf31]

Personally, this is my opinion...depending on what power you're planning on making the M3 OE Diff will not hold up, and you'll want to rebuild the diff at some point.

The M Variable diff is lacking in regards to lock up response and durability. A lot of people who either make a lot of power or track the car end up rebuilding or replacing the diff.

[TUN3D]

Kgolf31 > Thanks for the input. Looking at the numbers and availability, I'm leaning towards getting the MFactory LSD (got a pretty sweet deal). I don't track the car or autoX yet. My goal is 550-600whp -- 1/4mile. Eventually, I'd like to upgrade the suspension and get the M3 parts in there. I'm committed to getting my conversion as close as possible to a true 1M. For now though, I've been sitting on the turbo-upgrade for over a year-and-a-half. Would like to experience that.

[ShocknAwe]

Seems to me I'd be worrying more about LSD functionality and getting the suspension geometry right. Actually having the real M prop shaft, axles, etc doesn't seem like much of a necessity.

Especially if you're shooting for 600ish whp (and your torque will be up there too), I'd be looking at higher strength aftermarket components that are designed to handle that kind of torture.

[TZANIDO777]

Originally Posted by TUN3D

TZANIDO777 > That's a freakin' steel from what I'm finding. So far, I'm only finding bits and pieces. I got the subframe, LSD, Right & Left Complete Suspension Assembly (Axles, Control Arms, Spindle, Trailing Arms, etc.). I also found a complete brake set (rotor/calipers).

$0850.00 > LSD - ilikebmxbikes
$1088.94 > Rotors & Calipers
$0659.99 > R Suspension
$0849.99 > L Suspension
$0514.45 > Sub Frame
=========================
$3963.37 > Total

This doesn't include the shocks/springs or front suspension knuckles, etc.

You will also need the driveshaft from an M3 in order to make it work with the diff housing of the M3. The 1 series driveshaft will not bolt into the M3 diff housing. You will also need to measure your driveshaft and have the M3 one cut and balanced by a driveshaft shop or fabrication shop to fit in the 1 series.

I found a driveshaft for $500 and the shop I gave it to charged me $300 to cut, re-weld and balance the driveshaft. So you're looking at another $800.

I would have recommended to get a custom clutch type lsd like the GT4 drexler or a OS giken which are tuneable and better suited for road racing (some good threads on the different types and benefits of lsd on the m3forum) however you did mention you will not be doing that, just thought I would throw the option out there.

I am sure the M factory one will suit your needs for everyday and spirited driving.

[..]

Originally Posted by ilikebmxbikes

It can all be done in a day. The 135i brembos are inferior to the stock m3 brakes. Everything is an upgrade.

When you consider an LSD typically costs around $2200 for a pumpkin after core, m3 suspension (front and rear) is usually in the $2k range, sway bars are ~$400 and m3 subframe bushings are ~ $900 after labor - the upgrades I suggest really do come in as a bargain if your car does not have the above items and you get the m3 parts off of a salvage.

i purchased my Mfactory LSD w/ 3.08 final drive for $1,400 shipped... And yes, that the entire pumpkin.