F8X M3/M4 CF Drive shaft mod

[nextelbuddy]

I already sent this to a couple of people via PM, figured I would post it here in case others are interested in the future:

I did not do the actual welding, so I can't comment on that, the rest was fairly simple.

I bought the M4 driveshaft and a 330 driveshaft as donor for the flanches. Make sure you buy a 330 shaft that has the same end links as the M3. There are some weird different shaft variants out there for x drive or automatics.

I measured the OEM M3 driveshaft length in two dimensions: with the rear joint compressed and with the rear joint stretched and gave that Info to the welding company. They then mated the flanches to the m4 driveshaft and balanced it.

My measurements were:
1364 mm with joint compressed
1376 mm with join stretched

Installation was straightforward. The shaft is a bit thicker than the OEM steel pieces, but everything cleared fine. I did not have to do any changes to other parts. You will have to loosen your diff mounts to push it back and mate it to the shaft.

Unfortunately I did not weigh the part when I got it. The M4 shaft weighs 7,6 kg. it did feel considerably lighter with the E46 flanches on it (I would guess 5kg)

Also make sure to install a new ball joint and dont reuse one from some 330 shaft you buy used. It is BMW part 26117841003.

I'm curious at the end of the day, does it matter which variant of the CF driveshaft we get? there was a telescoping version and a non telescoping version. does getting the telescoping variant make it any easier to install with out having to loosen and move the differential? that just seems like an unnecessary paint point.

if the DS has 2 measurements of CV joint compressed vs uncompressed then the driveshaft shop that cuts and welds the flanges on, would be welding the CV joint end with the CV joint in the middle of its compression range right? so that when all said and done, the CF driveshaft would have the same dimensions as the M3 2 piece DS compressed vs uncompressed right?


or is the main issue that the 2 piece DS is easier to install because of the center support bearing and you can install both ends first and then push the CSB up into its mounting location vs the single one piece DS that doesn't have the CSB to allow flexibility with installing both ends first


i saw the video of the F8x CF driveshaft video installing the CF DS with the slip yoke? i assume we dont get that luxury since we are using CV joint not the slip yoke?

[Altaran]

The guy in the shop told me that he balanced it at 3500rpm. That it's the max rpm he could do, not sure if it's enough or the problem is elsewhere. Its not very noticeable, but i guess i will have adress that.
What RPM the driveshaft has at top speed?

Depends on your final drive ratio. If you have a shorter diff like me it can exceed 8k rpm at 250+ kph

There's a calculator online:

https://www.drive-lines.com/php10/dlrpm.php

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[RazorM]

I installed the driveshaft late last year, did not really have time to drive it much.
Installation was easy, i have SMG car, no problems with clearance. I am running original heat shields, did only slight adjustment of the shield on one place so it doesn’t make contact. Installed with new guibo and CV joint.
BUT there may be slight vibration in mine. Starting at 130kmh and it stopped around 150-160kmh. The guy in the shop told me that he balanced it at 3500rpm. That it’s the max rpm he could do, not sure if it’s enough or the problem is elsewhere. Its not very noticeable, but i guess i will have adress that.
What RPM the driveshaft has at top speed?

Weight of the original driveshaft without guibo and bolts was 8,21kg compared to M4 with guibo and bolts 7,38kg. Not sure how much guibo with bolts can weight, I would guess around 400-500g. Somebody can measure it. So it would total around 15% weight loss, 1,2kg/2,64lbs.

I sourced used shaft for 200€ and had it adapted and balanced for 300€. Plus new guibo 60€ and CV joint 200€.

[0-60motorsports]

Update coming soon y'all. Got a little sidetracked upgrading the M2's HPFP for some E85 boostie action, I'll have the driveshaft in this week.

Sounds good. Looking forward to the review.

[EthanolTurbo]

Update coming soon y'all. Got a little sidetracked upgrading the M2's HPFP for some E85 boostie action, I'll have the driveshaft in this week.

[x Spades x]

Bump... any update?

Also, what are the confirmed shops (and location) that can do these without issue?

[Nate047]

Bump. FINALLY Installing my revised F8x CF driveshaft this week and will be able to test and provide the details. Stay tuned.

In for details.

[0-60motorsports]

Anyone figured out or know of a place in Atlanta, GA that can do this mod for an SMG car if I provide all the parts?

[x Spades x]

Bump. FINALLY Installing my revised F8x CF driveshaft this week and will be able to test and provide the details. Stay tuned.

Where did you get yours installed again?

[Obioban]

Please drive irresponsibly quickly, assuming it feels smooth.
(since driveshaft speed is proportional to road speed, not engine speed).

not sure how viable it it for you, but I’d really like to know its smooth to at least 150, and ideally 175 (indicated).

[EthanolTurbo]

Bump. FINALLY Installing my revised F8x CF driveshaft this week and will be able to test and provide the details. Stay tuned.

[0-60motorsports]

Found a guy from Ontario on IG that has a pic with this mod done from February. Profile is @velart_motorsport
I don't know him, but if anyone here is looking for a good shop in North America to get this done, he might be worth reaching out to.

Mine now has 3500km on it and is still working fine. It survived a ring trackday, so full load is not an issue 😂

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Shipping to and from Canada is ridiculously high especially to Bahrain.

[Mike RT4]

Found a guy from Ontario on IG that has a pic with this mod done from February. Profile is @velart_motorsport
I don't know him, but if anyone here is looking for a good shop in North America to get this done, he might be worth reaching out to.

Mine now has 3500km on it and is still working fine. It survived a ring trackday, so full load is not an issue 😂

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The drive-shaft is probably wondering where all the torque went .

[Altaran]

Found a guy from Ontario on IG that has a pic with this mod done from February. Profile is @velart_motorsport
I don't know him, but if anyone here is looking for a good shop in North America to get this done, he might be worth reaching out to.

Mine now has 3500km on it and is still working fine. It survived a ring trackday, so full load is not an issue 😂

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[x Spades x]

Bump!