Complete E92 M3 rear end swap into 335IS... stay with XHP or go M3 GTS software???

Mvaccarelli01

Specialist
Apr 18, 2020
78
Hello everyone, I was looking at Facebook forums last night and found a deal I couldn't refuse. Someone a couple hours from me was selling a complete E92 m3 rear end, and I mean complete as in everything possible was there. 3.15 diff, brakes, rotors, driveshaft, axles, subframe, control arms ect everything bolted together in one unit ready to go. I drove straight down after work and I picked it up for $1450. Will post pictures soon!!

The question I have is what is the best route to go as far as software. I already have the XHP flash should I stay with it, as of now we can adjust the rear diff ratio to the correct settings from 2.56 to 3.15 and keep everything XHP has to offer, or should I get all the other necessary requirements to complete the m3 GTS flash. need some help.

Also while the whole rear end is out, I will be refreshing bushings to

Turner Solid Rear Subframe Bushing Set
I heard m3 guys love this setup with no increase NVH.

Purple poly powerflex differential bushings

after research saw this was best setup for performance with little NVH

Roque engineering transmission mounts
Nothing but great things from these on fourms

I already have a S55 Flywheel that has been waiting to go in. will be doing that

I want to sandblast and powercoat the subframe as there is some rust. There is also rust on driveshaft and LSD so will be cleaning that.


Also I have ST XTA coilovers all around, I saw that shock will not fit in the rear anymore, does anyone recommend what shock i can get, can i keep the ST spring and just get a different shocks for the m3??

Do you think the control arms bushings and everything need to be replaced? I am not sure how long this been out of the orginal car it looks like at least a year or more.
Let me know what other suggestions i should be doing while subframe is out.
 
Last edited:

derekgates

Lieutenant
Feb 23, 2018
654
NW FL
I am not sure how to sum up the process in a single reply. I spent 9 months swapping things over after aiding in 2018 with the discovery from @dyezak


If you want stronger axles, diff, driveshaft then go for the full swap with 3.15 (or change the R&P to 2.81).
If you want less work then try xHP and 2.56.


The downsides to 3.15 is the extremely short gearing and top end. 80MPH is close to 4k rpm when I am going down the interstate.
The downsides to xHP is 'odd behavior' at times. See https://bmw.spoolstreet.com/threads/xhp-dct-experience-thread.6637/

I love the M3 GTS software.
xHP is NOT compatible with the M3 GWS, btw.

I laugh at people that say Purple Powerflex diff bushings have 'little NVH'. That is the part of my install that I loathe at times. The diff whine is real.
I have poly subframe bushings, do not have experience with solid bushings.
I am also laughing at changing transmission mounts. I have some RE mounts that I had on car for less than 10k if you are interested. :p


Here are my notes in Evernote that I have collected when I did my last swap:


Be sure to buy new bolts for driveshaft and other bolts marked as 'must replace'. You will also need to sacrifice your driveshaft (cut it and weld onto the M3 driveshaft) if you are trying to swap the M3 rear. The M3 driveshaft is NOT a 'bolt in' replacement!

I do not think the M3 subframe is worth it; it is a ton of extra work, suspension is changed in rear so that strut/springs are incompatible... and you can't use a diff lockdown anymore (I have a custom diff lockdown on my setup).


I started the swap at around ... https://bmw.spoolstreet.com/threads/n54-dct-w-m3-conversion.3380/post-93937

Let me know if I can help with any info or photos...
 

Mvaccarelli01

Specialist
Apr 18, 2020
78
I am not sure how to sum up the process in a single reply. I spent 9 months swapping things over after aiding in 2018 with the discovery from @dyezak


If you want stronger axles, diff, driveshaft then go for the full swap with 3.15 (or change the R&P to 2.81).
If you want less work then try xHP and 2.56.


The downsides to 3.15 is the extremely short gearing and top end. 80MPH is close to 4k rpm when I am going down the interstate.
The downsides to xHP is 'odd behavior' at times. See https://bmw.spoolstreet.com/threads/xhp-dct-experience-thread.6637/

I love the M3 GTS software.
xHP is NOT compatible with the M3 GWS, btw.

I laugh at people that say Purple Powerflex diff bushings have 'little NVH'. That is the part of my install that I loathe at times. The diff whine is real.
I have poly subframe bushings, do not have experience with solid bushings.
I am also laughing at changing transmission mounts. I have some RE mounts that I had on car for less than 10k if you are interested. :p


Here are my notes in Evernote that I have collected when I did my last swap:


Be sure to buy new bolts for driveshaft and other bolts marked as 'must replace'. You will also need to sacrifice your driveshaft (cut it and weld onto the M3 driveshaft) if you are trying to swap the M3 rear. The M3 driveshaft is NOT a 'bolt in' replacement!

I do not think the M3 subframe is worth it; it is a ton of extra work, suspension is changed in rear so that strut/springs are incompatible... and you can't use a diff lockdown anymore (I have a custom diff lockdown on my setup).


I started the swap at around ... https://bmw.spoolstreet.com/threads/n54-dct-w-m3-conversion.3380/post-93937

Let me know if I can help with any info or photos...
Thank you for the reply, yeah your notes and info on your swap will be super useful. So you have stock transmission mounts back in your car as the Roque mounts were to much NVH? Do you have any idea what is the top speed at around 7k with the 3.15? If I did want to keep the m3 diff but go with the 2.81 How do i go about changing the R&P 2.81?
 

Lofuel

New Member
Feb 18, 2018
7
Philly
I’ll try to give you some of my insight, I did the whole swap pre XHP. The m3 gts software has worked flawless, love the adjustable LC on the cruise stick ,love drivelogic , new shifter setup , love the upgraded DS , axles , brakes, sway bar so on. I did the whole subframe swap like your looking to do. Just have to reuse your lower arms as the m3 are different where the strut bolts down , unless you get rear m3 struts. I run kw v2s what transformed the cars handling / feel with then LSD along with all the m3 suspension pieces. As derekgates said it is a lot of work / reading / parts but it’s all out there. I loved hardware upgrade , that was a big selling point to me.

would I have done it all of Xhp was out? Not sure since I never drove a car with it on to compare but both have its own pros and cons.The 3.15s are violent lol , with the dct your just banging the gears away but with the oem turbos is where it’s bad. Obviously they make no power after 5500 rpm so your always short shifting when all you want to do is wind the car out to redline.

I do have 2.81 gears I’m going to put in but I’m just finishing up a single turbo overhaul so I want to feel the 3.15s making power to redline before I swap them out. Top speed with the 3.15s on stockers I tried pushing hard to try to keep up with my brothers f10 m5 but I was out around 160 max on speedo so with speedo error prob 150s, in 7th at 6000rpm car makes no power. So If your keeping it to digs / 1/4 mile your fine. Half mile events forget it unless you have turbos to make power to redline. Anyway msg me if your need help if you go the m3 swap route or more detailed questions , I’m near Philly if your close by.
 

Mvaccarelli01

Specialist
Apr 18, 2020
78
I’ll try to give you some of my insight, I did the whole swap pre XHP. The m3 gts software has worked flawless, love the adjustable LC on the cruise stick ,love drivelogic , new shifter setup , love the upgraded DS , axles , brakes, sway bar so on. I did the whole subframe swap like your looking to do. Just have to reuse your lower arms as the m3 are different where the strut bolts down , unless you get rear m3 struts. I run kw v2s what transformed the cars handling / feel with then LSD along with all the m3 suspension pieces. As derekgates said it is a lot of work / reading / parts but it’s all out there. I loved hardware upgrade , that was a big selling point to me.

would I have done it all of Xhp was out? Not sure since I never drove a car with it on to compare but both have its own pros and cons.The 3.15s are violent lol , with the dct your just banging the gears away but with the oem turbos is where it’s bad. Obviously they make no power after 5500 rpm so your always short shifting when all you want to do is wind the car out to redline.

I do have 2.81 gears I’m going to put in but I’m just finishing up a single turbo overhaul so I want to feel the 3.15s making power to redline before I swap them out. Top speed with the 3.15s on stockers I tried pushing hard to try to keep up with my brothers f10 m5 but I was out around 160 max on speedo so with speedo error prob 150s, in 7th at 6000rpm car makes no power. So If your keeping it to digs / 1/4 mile your fine. Half mile events forget it unless you have turbos to make power to redline. Anyway msg me if your need help if you go the m3 swap route or more detailed questions , I’m near Philly if your close by.
Thank you so much for the reply! Great info I do have the doc 6266 full E85 with enough fuel to run however much boost I want can make power to redline. My worry is my mile per hour is going to be high 160s-low 170s possibly at the 1/2 mile don’t know if 3.15 to short of a gear unless I really rev out. Where do you source the 2.81 gears? You can just open the m3 differential up and drop in the 2.81 gears instead?
 

derekgates

Lieutenant
Feb 23, 2018
654
NW FL
Thank you so much for the reply! Great info I do have the doc 6266 full E85 with enough fuel to run however much boost I want can make power to redline. My worry is my mile per hour is going to be high 160s-low 170s possibly at the 1/2 mile don’t know if 3.15 to short of a gear unless I really rev out. Where do you source the 2.81 gears? You can just open the m3 differential up and drop in the 2.81 gears instead?


2.81
Tyre Circumference = 2077.22 mm
1st Gear = 60.31 km/h - 37.39 mph
2nd Gear = 94.34 km/h - 58.49 mph
3rd Gear = 133.9 km/h - 83.02 mph
4th Gear = 171.81 km/h - 106.52 mph
5th Gear = 207.41 km/h - 128.59 mph
6th Gear = 239.65 km/h - 148.58 mph
7th Gear = 262.09 km/h - 162.49 mph


2.56
1st Gear = 66.2 km/h - 41.05 mph
2nd Gear = 103.55 km/h - 64.2 mph
3rd Gear = 146.98 km/h - 91.13 mph
4th Gear = 188.59 km/h - 116.92 mph
5th Gear = 227.66 km/h - 141.15 mph
6th Gear = 263.05 km/h - 163.09 mph
7th Gear = 287.68 km/h - 178.36 mph



3.15 really sucks. On the straight at NOLA Motorsports I was coming close to redline at around 130MPH, so maybe 140-145MPH on 3.15?

 

Mvaccarelli01

Specialist
Apr 18, 2020
78
2.81
Tyre Circumference = 2077.22 mm
1st Gear = 60.31 km/h - 37.39 mph
2nd Gear = 94.34 km/h - 58.49 mph
3rd Gear = 133.9 km/h - 83.02 mph
4th Gear = 171.81 km/h - 106.52 mph
5th Gear = 207.41 km/h - 128.59 mph
6th Gear = 239.65 km/h - 148.58 mph
7th Gear = 262.09 km/h - 162.49 mph


2.56
1st Gear = 66.2 km/h - 41.05 mph
2nd Gear = 103.55 km/h - 64.2 mph
3rd Gear = 146.98 km/h - 91.13 mph
4th Gear = 188.59 km/h - 116.92 mph
5th Gear = 227.66 km/h - 141.15 mph
6th Gear = 263.05 km/h - 163.09 mph
7th Gear = 287.68 km/h - 178.36 mph



3.15 really sucks. On the straight at NOLA Motorsports I was coming close to redline at around 130MPH, so maybe 140-145MPH on 3.15?

How do you get the 2.81 to work with the m3 differential??? What do you have to do to get the 2.81
 

derekgates

Lieutenant
Feb 23, 2018
654
NW FL
How do you get the 2.81 to work with the m3 differential??? What do you have to do to get the 2.81
You have to find a R&P and get it installed in the diff. @LMB335is used one out of 850i but diffsonline.com can also help (for more cost): https://diffsonline.com/bmw-e9x-m3-dct-transmission-differentials.html

The 2.81 gear is 210mm and is a direct swap for the 3.15 gear. It came out of a 850i diff. Almost all the V8 BMWs of the 90's used 210mm gears.
$300 shipped. Diffsonline has their used ones starting at $500 and that's if he even has one. I got mine yesterday. Looked in excellent condition, teeth were all good, no obvious wear. Found a place to get the elusive pinion bearings as well. The only other place I found in the US was Diffsonline and the pair was $260 plus shipping. I found them for $100 cheaper.
 

derekgates

Lieutenant
Feb 23, 2018
654
NW FL
I would say that if the top MPH is important to you, try xHP. You can give it a shot without needing to do the swap.

Get a nice helical LSD for your current diff and rip it.
 

Mvaccarelli01

Specialist
Apr 18, 2020
78
I would say that if the top MPH is important to you, try xHP. You can give it a shot without needing to do the swap.

Get a nice helical LSD for your current diff and rip it.
Yes that’s the info I need awesome, I am going to stick with xhp and try to source a 2.81. I want to be best of all worlds and cannot do 1/2 mile track events at my power level with 3.15 will run out of gear lol. Will update thread with updates. Thanks a lot big help
 

Lofuel

New Member
Feb 18, 2018
7
Philly
2.81
Tyre Circumference = 2077.22 mm
1st Gear = 60.31 km/h - 37.39 mph
2nd Gear = 94.34 km/h - 58.49 mph
3rd Gear = 133.9 km/h - 83.02 mph
4th Gear = 171.81 km/h - 106.52 mph
5th Gear = 207.41 km/h - 128.59 mph
6th Gear = 239.65 km/h - 148.58 mph
7th Gear = 262.09 km/h - 162.49 mph


2.56
1st Gear = 66.2 km/h - 41.05 mph
2nd Gear = 103.55 km/h - 64.2 mph
3rd Gear = 146.98 km/h - 91.13 mph
4th Gear = 188.59 km/h - 116.92 mph
5th Gear = 227.66 km/h - 141.15 mph
6th Gear = 263.05 km/h - 163.09 mph
7th Gear = 287.68 km/h - 178.36 mph



3.15 really sucks. On the straight at NOLA Motorsports I was coming close to redline at around 130MPH, so maybe 140-145MPH on 3.15?

Yea I doubt I was even in the 150s when I was pushing it so hard to try to stay with my brothers m5 lol it is
Thank you so much for the reply! Great info I do have the doc 6266 full E85 with enough fuel to run however much boost I want can make power to redline. My worry is my mile per hour is going to be high 160s-low 170s possibly at the 1/2 mile don’t know if 3.15 to short of a gear unless I really rev out. Where do you source the 2.81 gears? You can just open the m3 differential up and drop in the 2.81 gears instead?

Awesome setup , I did the 6466 gen 2 BB with the jpworkz twin scroll top mount , with a good amount of fuel also (twin 450s bucketless with the Holly hydramats) and been running the helix for 5 months now with no issues so I’ll continue to use that for now. So here’s some pics with the dct with a 285/30 19 tire what I been running. With the 2.81s @ 7200 your knocking on 200 mph , but you can compare to the 3.15s at the higher rpms with those charts . I really want to drive a dct with xhp to compare them, but good luck ! Either way as long as you do the LSD it transforms the car
 

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