E9x M3 rear end swap

sizablepants · 12-22-2022, 03:56 PM

I was able to secure an e92 m3 rear end for 1,800 to swap in to my Manual 2008 135i.
I was going to just do a pumpkin differential but decided to do a complete rear end swap for better control arms, axles, bushings, subframe, sway bar. After I remove my 135i rear end I should be able to sell all parts for around 1,000 leaving me with a cheap LSD and a stronger rear end in general.

I have everything planned out for driveshaft removal (and refitting) and bushing replacement but I haven't been able to find out if I need to swap the brakes/hubs from my 135i on to the m3 rear end. Will I need to swap them or will the M3 hub and brakes be plug and play?

The M3 brakes look like they aren't as good as the 135i brakes, why is that?

amg6975 · 12-22-2022, 04:04 PM

The M3 brakes are far better than the 135, front and rear. They just don't look as flashy. You should be fine with M3 rears and 135 fronts, or swap to 335i fronts. M3 master cylinder will help your pedal feel in this configuration.

The M3 hubs are 10mm per side more narrow than the 135 so if you want your wheel offsets to be the same you'll need 10mm spacers. If not, it actually helps wheel selection quite a lot because you don't need such a high offset rear wheel.

sizablepants · 12-22-2022, 04:34 PM

amg6975 Thank you!

bbnks2 · 12-22-2022, 07:53 PM

Quote:

Originally Posted by sizablepants

I was able to secure an e92 m3 rear end for 1,800 to swap in to my Manual 2008 135i.
I was going to just do a pumpkin differential but decided to do a complete rear end swap for better control arms, axles, bushings, subframe, sway bar. After I remove my 135i rear end I should be able to sell all parts for around 1,000 leaving me with a cheap LSD and a stronger rear end in general.

I have everything planned out for driveshaft removal (and refitting) and bushing replacement but I haven't been able to find out if I need to swap the brakes/hubs from my 135i on to the m3 rear end. Will I need to swap them or will the M3 hub and brakes be plug and play?

The M3 brakes look like they aren't as good as the 135i brakes, why is that?

you just need to keep your E82 e-brake cables. The e9x cables are longer (obviously) and will be took long on the E82 chassis. Otherwise, the M3 rear-end bolts right up. I highly recommend that you do the RSFB and the rear MID brakes lines at this time. Consider adding aftermarket rear sway bar bushings too. These three things are a PITA to do with the sub frame mounted and cheap/easy enough to do while the subframe is out..

sizablepants · 01-11-2023, 11:31 AM

Quote:

Originally Posted by bbnks2

you just need to keep your E82 e-brake cables. The e9x cables are longer (obviously) and will be took long on the E82 chassis. Otherwise, the M3 rear-end bolts right up. I highly recommend that you do the RSFB and the rear MID brakes lines at this time. Consider adding aftermarket rear sway bar bushings too. These three things are a PITA to do with the sub frame mounted and cheap/easy enough to do while the subframe is out..

The brake lines that are connected to the subframe were cut by the dismantlers unfortunately, I was just going to transfer my brake lines from my 135i. (assuming everything will transfer over without any trouble.) Should I just get brand new lines?

bbnks2 · 01-13-2023, 01:26 PM

Quote:

Originally Posted by sizablepants

The brake lines that are connected to the subframe were cut by the dismantlers unfortunately, I was just going to transfer my brake lines from my 135i. (assuming everything will transfer over without any trouble.) Should I just get brand new lines?

you need to use the ones from your 135i...

amg6975 · 01-16-2023, 08:15 AM

Quote:

Originally Posted by sizablepants

The brake lines that are connected to the subframe were cut by the dismantlers unfortunately, I was just going to transfer my brake lines from my 135i. (assuming everything will transfer over without any trouble.) Should I just get brand new lines?

If you're talking about the ones between the chassis and the subframe then yes, they're all the same. If you're talking about subframe to brakes they are not.

bbnks2 · 01-18-2023, 07:52 AM

Quote:

Originally Posted by amg6975

If you're talking about the ones between the chassis and the subframe then yes, they're all the same. If you're talking about subframe to brakes they are not.

yeah mis-read that. The brake lines themselves you can keep.

sizablepants · 01-18-2023, 06:12 PM

Quote:

Originally Posted by bbnks2

yeah mis-read that. The brake lines themselves you can keep.

Great, I appreciate the help. I discovered a leak from the engine so I will be doing a ofhg, valve cover gasket, and crank seal guard and crank hub capture before getting to the the rear end swap. both should be done in 3-4 weeks.

CalvinNismo · 01-21-2023, 08:30 AM

Quote:

Originally Posted by bbnks2

Consider adding aftermarket rear sway bar bushings too.

What ones would you go for? The standard M3 ones seem loads better than the non-M ones.

A97syclone · 04-13-2023, 08:02 AM

I am also the proud owner of a new M3 complete rear subframe. Any suggestions on upgrades before putting it in the car? I plan on daily/drag/road race. It will have a 6.2L LS.
I have M4 brakes to install, I plan on swapping the M3 diff for an 8.8 axle and doing the solid subframe bushings.
Anything else I should change/upgrade?

lab_rat · 04-18-2023, 10:57 PM

Quote:

Originally Posted by A97syclone

I am also the proud owner of a new M3 complete rear subframe. Any suggestions on upgrades before putting it in the car? I plan on daily/drag/road race. It will have a 6.2L LS.
I have M4 brakes to install, I plan on swapping the M3 diff for an 8.8 axle and doing the solid subframe bushings.
Anything else I should change/upgrade?

Edit:

Just found your build thread.

I have been *really* interested in following these LS swap builds lately.

12-22-2022, 03:56 PM	#1
sizablepants Private 9 Rep 56 Posts Drives: '08 135i @Driving_This_Daily Join Date: Dec 2019 Location: Los Angeles iTrader: (0)	E9x M3 rear end swap I was able to secure an e92 m3 rear end for 1,800 to swap in to my Manual 2008 135i. I was going to just do a pumpkin differential but decided to do a complete rear end swap for better control arms, axles, bushings, subframe, sway bar. After I remove my 135i rear end I should be able to sell all parts for around 1,000 leaving me with a cheap LSD and a stronger rear end in general. I have everything planned out for driveshaft removal (and refitting) and bushing replacement but I haven't been able to find out if I need to swap the brakes/hubs from my 135i on to the m3 rear end. Will I need to swap them or will the M3 hub and brakes be plug and play? The M3 brakes look like they aren't as good as the 135i brakes, why is that?
	Appreciate 0 Tweet Quote

12-22-2022, 04:04 PM	#2
amg6975 Captain 500 Rep 645 Posts Drives: '12 M1.5, '05 ZHP, '98 M3/4/5 Join Date: May 2017 Location: Rochester NY iTrader: (0)	The M3 brakes are far better than the 135, front and rear. They just don't look as flashy. You should be fine with M3 rears and 135 fronts, or swap to 335i fronts. M3 master cylinder will help your pedal feel in this configuration. The M3 hubs are 10mm per side more narrow than the 135 so if you want your wheel offsets to be the same you'll need 10mm spacers. If not, it actually helps wheel selection quite a lot because you don't need such a high offset rear wheel.
	Appreciate 1 lab_rat394.50 Quote

12-22-2022, 04:34 PM	#3
sizablepants Private 9 Rep 56 Posts Drives: '08 135i @Driving_This_Daily Join Date: Dec 2019 Location: Los Angeles iTrader: (0)	amg6975 Thank you!
	Appreciate 0 Quote

04-13-2023, 08:02 AM	#11
A97syclone Private 68 Rep 69 Posts Drives: '11 128i Join Date: Mar 2022 Location: Phoenix iTrader: (0)	I am also the proud owner of a new M3 complete rear subframe. Any suggestions on upgrades before putting it in the car? I plan on daily/drag/road race. It will have a 6.2L LS. I have M4 brakes to install, I plan on swapping the M3 diff for an 8.8 axle and doing the solid subframe bushings. Anything else I should change/upgrade?
	Appreciate 0 Quote