F8X M3/M4 CF Drive shaft mod

[0-60motorsports]

Hello everyone. Stumbled across this thread about a week ago and was inspired to get to work.
Would like to preface the following by saying that I was the first (at least to document it) to retrofit an F8x driveshaft onto my E82 back in September 2021 so I had a good idea of what I'm up against here. All measurements and weights posted were taken by me as in the past I've learned (the hard way) that internet measurements can be misleading.

Began by purchasing an F8x driveshaft off of a 2016 M4 coupe, part number 26107857629. It's important that you get this one, NOT part number 26117855000 as 7629's transmission-side flange is a slip-on joint that allows for 2" of travel, thus absorbing any play in the drivetrain (also making installation easier) instead of the now-missing center support bearing. 5000 does not feature the slip-on joint but instead is a fixed, welded piece. Our OEM E46M3 guibo does not fit this F8x flange so some modifications had to be done-- a local machine shop ovaled out the flange holes to accomodate the guibo holes. Worth mentioning that I ran the same style modification on the F8x driveshaft that ended up on my 790whp 8k RPM 200mph 135i 3 years ago-- no issues. Local driveshaft shop welded shortened the F8x driveshaft to my desired length and welded on the diff-side portion of the E46M3 shaft allowing for the traditional OEM CVJ to be used.

Now some measurements--
OEM guibo: 32mm
Fully dressed E46M3 DS: 1,403.5mm
Naked E46M3 DS (no guibo): 1,371.5mm
Resting position F8x DS (with guibo): 1,463.5mm
Fully compressed F8x DS (with guibo): 1,433.5mm
Fully expanded F8x DS (with guibo): 1,483mm
F8x slip-on joint play: 54mm
Modified F8x DS resting position: 1,397mm
Modified F8x DS fully compressed: 1375.5mm
Modified F8x DS fully expanded: 1,429mm

Weights:
Guibo: 1.4lbs
CVJ: 3.1lbs
Install-ready OEM E46M3 DS: 18.7lbs
Install-ready F8x DS (+E46M3 CVJ): 18.3lbs
Install-ready modified F8x DS: 17.6lbs

Cost:
F8x DS: $180
Flange holes machining: $100
DS shortening/balancing: $200
OEM CVJ: $360
OEM Guibo: $90
Donor E46M3 DS: $100
Total: $1,030
If your guibo and CVJ are in good shape and you don't mind sacrificing your existing E46M3 DS this mod can be done for $480, worth it in my opinions considering you never have to worry about your center support bearing ever again and frankly, it's just plain cool.

In conclusion, I was definitely surprised to learn about the weight differences between the F8x CF DS and our oem (steel by the way, surprisingly not aluminum!) E46M3 DS. I thought they would be more drastic. Either way I'm gearing up to install the new piece tomorrow and if all goes well I've got a spirited drive planned for Thursday morning, will update regarding installation difficulty and driving impressions.

Awesome post! Thank you for all the data. Would the shop you used do this for us if we shipped them the DS and parts?

[Bry5on]

Wonder if you could just swap the transmission output flange and use the bigger guibo instead of redrilling while still avoiding shift selector contact. Interesting info on the telescoping version of the shaft.

[1spool]

Hello everyone. Stumbled across this thread about a week ago and was inspired to get to work.
Would like to preface the following by saying that I was the first (at least to document it) to retrofit an F8x driveshaft onto my E82 back in September 2021 so I had a good idea of what I'm up against here. All measurements and weights posted were taken by me as in the past I've learned (the hard way) that internet measurements can be misleading.

Began by purchasing an F8x driveshaft off of a 2016 M4 coupe, part number 26107857629. It's important that you get this one, NOT part number 26117855000 as 7629's transmission-side flange is a slip-on joint that allows for 2" of travel, thus absorbing any play in the drivetrain (also making installation easier) instead of the now-missing center support bearing. 5000 does not feature the slip-on joint but instead is a fixed, welded piece. Our OEM E46M3 guibo does not fit this F8x flange so some modifications had to be done-- a local machine shop ovaled out the flange holes to accomodate the guibo holes. Worth mentioning that I ran the same style modification on the F8x driveshaft that ended up on my 790whp 8k RPM 200mph 135i 3 years ago-- no issues. Local driveshaft shop welded shortened the F8x driveshaft to my desired length and welded on the diff-side portion of the E46M3 shaft allowing for the traditional OEM CVJ to be used.

Now some measurements--
OEM guibo: 32mm
Fully dressed E46M3 DS: 1,403.5mm
Naked E46M3 DS (no guibo): 1,371.5mm
Resting position F8x DS (with guibo): 1,463.5mm
Fully compressed F8x DS (with guibo): 1,433.5mm
Fully expanded F8x DS (with guibo): 1,483mm
F8x slip-on joint play: 54mm
Modified F8x DS resting position: 1,397mm
Modified F8x DS fully compressed: 1375.5mm
Modified F8x DS fully expanded: 1,429mm

Weights:
Guibo: 1.4lbs
CVJ: 3.1lbs
Install-ready OEM E46M3 DS: 18.7lbs
Install-ready F8x DS (+E46M3 CVJ): 18.3lbs
Install-ready modified F8x DS: 17.6lbs

Cost:
F8x DS: $180
Flange holes machining: $100
DS shortening/balancing: $200
OEM CVJ: $360
OEM Guibo: $90
Donor E46M3 DS: $100
Total: $1,030
If your guibo and CVJ are in good shape and you don't mind sacrificing your existing E46M3 DS this mod can be done for $480, worth it in my opinions considering you never have to worry about your center support bearing ever again and frankly, it's just plain cool.

In conclusion, I was definitely surprised to learn about the weight differences between the F8x CF DS and our oem (steel by the way, surprisingly not aluminum!) E46M3 DS. I thought they would be more drastic. Either way I'm gearing up to install the new piece tomorrow and if all goes well I've got a spirited drive planned for Thursday morning, will update regarding installation difficulty and driving impressions.

[TheElite///M3]

i'm waiting on a new guibo and diff bushings and then i'll share my findings

[bigjae46]

So I guess everyone is waiting for these results from EthanolTurbo, before they finaliex

I think so.

[x Spades x]

You can use the shop that EthanolTurbo used. All you need to supply is the carbon driveshaft. I think its less than a week turn around plus shipping.

It hasn't been tested with success yet so proceed at your own risk. I think the shaft that EthanolTurbo received hasn't been tested since it was re-done. I don't see why there would be an issue once the length is corrected.

So I guess everyone is waiting for these results from EthanolTurbo, before they finaliex

[bigjae46]

Maybe I just don't understand what the order/purchase process is now.

If we have a CF driveshaft, and we want this done... what is the process? Who is the shop doing it? If we have an SMG, are they adjusting accordingly? There was talk about needing ends from other cars, does this shop have those in stock (or can source them)? Is there a group buy set up?

You can use the shop that EthanolTurbo used. All you need to supply is the carbon driveshaft. I think its less than a week turn around plus shipping.

It hasn't been tested with success yet so proceed at your own risk. I think the shaft that EthanolTurbo received hasn't been tested since it was re-done. I don't see why there would be an issue once the length is corrected.

[Altaran]

Maybe I just don't understand what the order/purchase process is now.

If we have a CF driveshaft, and we want this done... what is the process? Who is the shop doing it? If we have an SMG, are they adjusting accordingly? There was talk about needing ends from other cars, does this shop have those in stock (or can source them)? Is there a group buy set up?

You are going to need to source a 330 shaft separately unless you don't mind sacrificing your original shaft. I guess it's possible to find a shop to search and buy one for you. But that would just jack the price up, at the end it's extra labor hours for them in front of the computer.

You do not need a different length for smg. It's essentially the same gearbox, same driveshaft length. There is also only one stock driveshaft part number, no separate version for smg. The only problem will be to see if the M4 CF shaft clears the shift actuator. Since the CF shaft is thicker, I don't know if it clears. The best solution will be if somebody doing it with a six speed has a buddy with smg to test fit it for clearance.

Since it's all manual labor with welding and balancing I don't see how a group buy would drive down cost. Only makes sense if there is machine setup involved.

Gesendet von meinem Pixel 7 mit Tapatalk

[x Spades x]

Based on this message it looks like it’s standing still at least in part because you’re not taking any action you’ve got all the same hardware and resources as the other folks in the thread. Just poking fun.

Maybe I just don't understand what the order/purchase process is now.

If we have a CF driveshaft, and we want this done... what is the process? Who is the shop doing it? If we have an SMG, are they adjusting accordingly? There was talk about needing ends from other cars, does this shop have those in stock (or can source them)? Is there a group buy set up?

[Bry5on]

Gotcha.
I guess it just seems like it's beit's a stand still. I have this driveshaft just sitting here waiting for a shop confirmation, process, and confirmed testing results of performance (zero vibration, etc). Us SMG users have an extra layer as well.

Based on this message it looks like it’s standing still at least in part because you’re not taking any action you’ve got all the same hardware and resources as the other folks in the thread. Just poking fun.

[0-60motorsports]

Gotcha.
I guess it just seems like it's beit's a stand still. I have this driveshaft just sitting here waiting for a shop confirmation, process, and confirmed testing results of performance (zero vibration, etc). Us SMG users have an extra layer as well.

LOL right there with ya brother!!!! Hopefully soon. Otherwise I'll have to get my hands dirty later on this year when I'm over there (like I did with the SMG relocation hydraulic lines drama).

[x Spades x]

Altaran's worked fine, I got mine re-shortened to the proper length, just haven't reinstalled it yet. I haven't driven my E46 in 3 months so once I get it back on the road I'll resume testing.

Gotcha.
I guess it just seems like it's beit's a stand still. I have this driveshaft just sitting here waiting for a shop confirmation, process, and confirmed testing results of performance (zero vibration, etc). Us SMG users have an extra layer as well.

[0-60motorsports]

I am sure once someone has the shop to do the mod locked down (a reliable and reputable source with shipping service) this mod will start to take off. Like I said if someone can assist with a solid shop in getting this done for me in the States i will happily buy a CF DS and ship it direct to the shop. Or i'll just wait when i am back over and have it done locally myself. I'll still need to know the length for and SMG car though.

[EthanolTurbo]

How though? This has been over a year, and it seems dead as of now. Two people testing with no word

Altaran's worked fine, I got mine re-shortened to the proper length, just haven't reinstalled it yet. I haven't driven my E46 in 3 months so once I get it back on the road I'll resume testing.

[x Spades x]

I know it's only the one account and probably not much of a mod for the faint hearted. But so far seems pretty promising.

How though? This has been over a year, and it seems dead as of now. Two people testing with no word