E92 M3 Rear Subframe + Diff upgrade

[135i2]

Best result is fitting the full Monty as many have done. The entire, stronger M3 cradle, diff, axles and hubs. The whole shebang is pretty much plug n play if you grab the front yoke with the diff. I tossed the M3 brakes for a big brake kit. Why would you want to keep the 135 axles over M3/1M if available? No master cylinder change required.

[houtan]

Originally Posted by 135i2

Best result is fitting the full Monty as many have done. The entire, stronger M3 cradle, diff, axles and hubs. The whole shebang is pretty much plug n play if you grab the front yoke with the diff. I tossed the M3 brakes for a big brake kit. Why would you want to keep the 135 axles over M3/1M if available? No master cylinder change required.

I'm with you. But none of the m3 diffs come close to the 2.56 ratio in the 135i dct. I have all the rear arms, rear m3 shock, my rear end feels real good and planted. Just looking ahead possibly to upgrade the brakes. A bbk is so expensive. Would be nice if I can understand if the m3 brakes will work in the rear if I use the hub carriers from an m3. Will the m3 rotor work with the 1 series e brake?

Once I understand the rear, I can just keep an eye out for a used set of parts and upgrade the brakes for low cost. Does that make sense?

[135i2]

All the info you need is at the start of this thread.

E brake is not an issue.

Plenty of after market diff centres available in a myriad of ratios.

You have to pay to play.

[Griffster]

Just checking.. does the year matter? I've found a 2007 E92 6MT M3 wrecking, an issues fitting this into a 2009 135i ?

[froop]

The year doesn't matter. What would matter however is the transmission. If you have a manual transmission you're going to want to get a DCT M3 LSD due their closer final drive ratios. A 6MT M3 LSD is ok if you have a 6AT 135i.

[135i2]

I have the 3.85 manual M3 ratio in my auto and its silly with high power levels. Come to think of it first gear is basically useless regardless, so I would opt for the DCT 3.15 even with an auto.

[flinchy]

Originally Posted by 135i2

Best result is fitting the full Monty as many have done. The entire, stronger M3 cradle, diff, axles and hubs. The whole shebang is pretty much plug n play if you grab the front yoke with the diff. I tossed the M3 brakes for a big brake kit. Why would you want to keep the 135 axles over M3/1M if available? No master cylinder change required.

If you wanted to fit the M3 brakes though, master cylinder should be changed as it's different to the original 135 one - Then could go an M3 BBK

not that it would be a major issue, just doing it all right.

[135i2]

Originally Posted by flinchy

If you wanted to fit the M3 brakes though, master cylinder should be changed as it's different to the original 135 one - Then could go an M3 BBK

not that it would be a major issue, just doing it all right.

Have rear M3 BBK on rear due to hubs and 135 BBK on front, Flinchy. Still running the 135 master cyl.

[flinchy]

Originally Posted by 135i2

Have rear M3 BBK on rear due to hubs and 135 BBK on front, Flinchy. Still running the 135 master cyl.

yeah not saying it won't work or anything, of course it will. just swapping the master cyl especially if anyone was to do the M *front* brakes is the way to go to have it properly sized.

[woosh]

Originally Posted by flinchy

yeah not saying it won't work or anything, of course it will. just swapping the master cyl especially if anyone was to do the M *front* brakes is the way to go to have it properly sized.

What are you driving nowadays?

[DR-JEKL]

I have M3 brakes with 335i master cylinder and at high speeds the pedal feel is a tad doughy...

<100 km/h you dont notice it but at high speeds it definately doesnt feel reassuring. Ive had a M3 M/C in the garage now for 6 months I'll get around to installing it eventually when I get the car back and update this thread for my feedback once fitted.

[flinchy]

Originally Posted by woosh

What are you driving nowadays?

Diesel golf

Its really hard to find a 135 with no sunroof.

[woosh]

Originally Posted by flinchy

Diesel golf

Its really hard to find a 135 with no sunroof.

lol

just get a mk4 supra man.

[flinchy]

Originally Posted by woosh

lol

just get a mk4 supra man.

Hah I wish

Haven't checked prices for them lately?

More exxy than an e82!

[woosh]

Originally Posted by flinchy

Hah I wish

Haven't checked prices for them lately?

More exxy than an e82!

Thats for an RZ haha

[flinchy]

Originally Posted by woosh

Thats for an RZ haha

When you want an RZ but all you can afford is an auto SZ

[bbnks2]

Just finished up this swap...

2011
135i
N55
6MT
3.08-->3.15

I swapped in the entire rear end of an E92 DCT M3. I used my stock driveshaft and had a shop cut and weld the M3 differential end on. The driveshaft sits recessed about 1/4" inside the diff flange. Measuring from the inside lip of the diff flange to the center support bearing mount bolt hole came out to 28 5/16".

You need to reuse your stock e-brake cable. The M3 cables are too long for the 135i. I did not think to do this and I now have a gerryrigged e-brake cable lol I will have to fix it later.

You are not supposed to re-use the ZNS bolts that are used on the diff flange. You need 6 new bolts. Make sure you have the reinforcements too (3x). There are no washers or nuts used on the diff flange. I did have blue paint marks so I threw a stainless steel M10 washer onto that bolt. No resulting vibrations as far as I can tell...

I reused my stock strut mounts so I didn't have to buy M3 struts (for now).

Brake bias feels much better with the larger M3 rear calipers and rotors. I kept the stock M3 pads in the rear and I run PFC08 up front. The car doesn't stand up on it's front end anymore under heavy braking (there was too much front bias stock). I gave it a few hard stops and the front still locks up first which is desirable so I feel it is a good move to use the M3 brakes as it creates more stable braking on a MODIFIED suspension car and did not result in the rear tires locking up. The car seems to stop shorter now with more rear bias but I did nothing scientific to prove it...

Finally, make sure you buy an M3 specific rear diff mount. That is the only bushing that is different. I ordered a 135i kit and was not able to use the rear diff mount. It was way too big.

[The Blimp]

Originally Posted by bbnks2

I swapped in the entire rear end of an E92 DCT M3.

Do you mind telling me how much you paid for the whole subframe? I just paid $950 for the drive shaft and half shafts, and am looking around for the 3.85 diff.

[135i2]

I have a low km M3 3.85 in my car and am going to swap it out for a 3.15 I have. The 3.85 might go up for sale if I like the 3.15. It has 7k on it or less.

[The Blimp]

Originally Posted by 135i2

I have a low km M3 3.85 in my car and am going to swap it out for a 3.15 I have. The 3.85 might go up for sale if I like the 3.15. It has 7k on it or less.

Why are you thinking of going with the 3.15, isnt that too tall?

[135i2]

The 3.85 combined with single turbo is a little crazy on full on boost. The 3.15 should make it a little easier to hoof, we'll see.

[bbnks2]

Originally Posted by The Blimp

Do you mind telling me how much you paid for the whole subframe? I just paid $950 for the drive shaft and half shafts, and am looking around for the 3.85 diff.

I paid $1700 for the entire rear end. I thought that was a fair price. I wouldn't have paid much more than $2k since the "part out" price wouldn't yield much more than that if at all (based off EBAY prices).

Driveshaft cost me $225 to have cut and re-tubed. The CV joint in the driveshaft that came with my rear end was a bit mangled up from being pulled. Took a bit of extra work to fix.

I also had to buy the diff bolts and flanges since they are not reusable. Got those at a dealer for $40. Brake fluid another $72. Redline Diff fluid $65. Then there is the alignment and the coding if you need to pay for those things.

All in it was a great experience. Nothing was "hard" in that I felt it was necessary to document to let others know about... Took me about 20 hours on my back in my driveway to drop the old sub-frame, prep the new one, and to install the new one. An entire day (8 hours) was spent prepping the new sub-frame (painting, pressing out bushings, cleaning, greasing, and installing adjustable arms).

I did not bother to un-do the 50mm nut on the stock shaft. I just had the shop cut the shaft off lol.

Also, I used the M3 sway. One thing to note, the bushings on the M3 sway are designed to BIND on the bar. This means the sway bar will also contribute to not only cornering roll rate but also wheel rate during acceleration (squat). This is not desirable imo so I bored out the M3 sway bar bushings a bit. The M3 rear sway bar can now rotate freely and will only contribute to the effective wheel rate during roll.