F8X M3/M4 CF Drive shaft mod

[EthanolTurbo]

If the shaft is too long or too short, even by a few millimeters, your CV could be bottomed out. Worth asking Kevin how much free travel there was in the CV on install.

Also, if the flange at the transmission wasn’t welded very orthogonal, or the CV coaxial, it could balance well but still vibrate, depending on how they fixtured it for balancing.

These questions and the ones Epsilon posed are why I have to discontinue effort on this project. The juice isn't worth the squeeze at this point being this deep in.

Edit: the more I think about this, the more I think they botched the job. People have done this mod on E9x M3s with no vibration issues. These driveshafts were mostly pulled off running cars. It sounds like even one thing can set the balance off on these things so who's to say they took that into account?

[Bry5on]

If the shaft is too long or too short, even by a few millimeters, your CV could be bottomed out. Worth asking Kevin how much free travel there was in the CV on install.

Also, if the flange at the transmission wasn’t welded very orthogonal, or the CV coaxial, it could balance well but still vibrate, depending on how they fixtured it for balancing.

[Epsilon]

Here's my impressions and notes now having driven the converted shaft.

I guess the next question is WHY? It was balanced by the driveshaft shop and they said it balanced fine. Is the CF driveshaft itself causing vibration? Wouldn't a vibration this bad turn up on the balancing test?

Totally bummer to hear.

What's the RPM at which they tested to balance the DS. Was the test visual or computer aided? Nuts and bolts torqued to spec? Did you double check the length of the welded carbon DS? Guibo installed in the proper direction?

Probably need more data points from other folks to see if this is a single occurrence.

[discoelk]

X2 on thanks for the effort.

Having chased driveline vibrations on other cars, Id be weary to try a mod like this given how much of a pain removing the driveshaft is on an E46M.

[ugaexploder]

Here's my impressions and notes now having driven the converted shaft.

First, the good: it does indeed tighten everything up, makes the car feel more powerful, and makes shifting better. It further reduces M Clunk, and is overall very beneficial for drivetrain feeling and connectedness.

Now, for the bad: past 80 mph it vibrates like crazy through the whole chassis and gets worse as speeds increase. I'm very sensitive to NVH so this is completely unacceptable to me.

I guess the next question is WHY? It was balanced by the driveshaft shop and they said it balanced fine. Is the CF driveshaft itself causing vibration? Wouldn't a vibration this bad turn up on the balancing test?

I'm frustrated because this is a great mod that helps tighten up the clunky stock drivetrain and it's relatively cheap. Unfortunately I can't recommend it at this time because it's a dice roll: is the shaft bad already? Does the conversion potentially cause vibration? I wouldn't want anyone else to feel this frustration and disappointment. Plus it's annoying to have to swap back and forth.

For me personally, I don't have the time, patience, or money to take it back, have it rebalanced and try it again. I guess if I had to do it over again, I would grab one of Matt@Euroconnex's YMCA CF shafts and put it on a credit card for peace of mind in case it's a POS.

Sorry guys. I wanted this to be a great mod for the community. If someone else wants to step up to the plate and try it themselves, YMMV but there is potential. If someone else tries it and it works, maybe I can take mine to get fixed.

Really appreciate you going through all the trouble to make this happen and report your findings.

[EthanolTurbo]

Here's my impressions and notes now having driven the converted shaft.

First, the good: it does indeed tighten everything up, makes the car feel more powerful, and makes shifting better. It further reduces M Clunk, and is overall very beneficial for drivetrain feeling and connectedness.

Now, for the bad: past 80 mph it vibrates like crazy through the whole chassis and gets worse as speeds increase. I'm very sensitive to NVH so this is completely unacceptable to me.

I guess the next question is WHY? It was balanced by the driveshaft shop and they said it balanced fine. Is the CF driveshaft itself causing vibration? Wouldn't a vibration this bad turn up on the balancing test?

I'm frustrated because this is a great mod that helps tighten up the clunky stock drivetrain and it's relatively cheap. Unfortunately I can't recommend it at this time because it's a dice roll: is the shaft bad already? Does the conversion potentially cause vibration? I wouldn't want anyone else to feel this frustration and disappointment. Plus it's annoying to have to swap back and forth.

For me personally, I don't have the time, patience, or money to take it back, have it rebalanced and try it again. I guess if I had to do it over again, I would grab one of Matt@Euroconnex's YMCA CF shafts and put it on a credit card for peace of mind in case it's a POS.

Sorry guys. I wanted this to be a great mod for the community. If someone else wants to step up to the plate and try it themselves, YMMV but there is potential. If someone else tries it and it works, maybe I can take mine to get fixed.

[Obioban]

I grew up in Glenside, PA...the home of Beaver College. Which was a woman's liberal art college. They've since changed the name to Altria or something.

Intercourse, PA is next to Blue Ball, PA... and not far from Hand Place, PA.

None of the above is made up.

We should probably get back to talking about shafts.

[ugaexploder]

...

There's a town called cumming?

I thought Intercourse, PA was bad.


If I didn't already have one, I'd pay the extra for a BNIB one for $750.

It’s definitely something you never get used to! 🤣🤣🤣

[bigjae46]

...

There's a town called cumming?

I thought Intercourse, PA was bad.


If I didn't already have one, I'd pay the extra for a BNIB one for $750.

I grew up in Glenside, PA...the home of Beaver College. Which was a woman's liberal art college. They've since changed the name to Altria or something.

[Obioban]

...

There's a town called cumming?

I thought Intercourse, PA was bad.


If I didn't already have one, I'd pay the extra for a BNIB one for $750.

[ugaexploder]

Oh then that's a bargain.

thinking about picking one up
unsure about this mod though, waiting for the brave souls to try this out first!

[0-60motorsports]

In all fairness, they are brand new

Oh then that's a bargain.

[ugaexploder]

Nice rip off deal. They weren't more than $300 on eBay. What's a shame.

In all fairness, they are brand new

[0-60motorsports]

For the ATL guys, there is a guy in ATLBIMMERS with (12) new f8x driveshafts for sale in Cumming. 750 obo

Nice rip off deal. They weren't more than $300 on eBay. What a shame.

[ugaexploder]

For the ATL guys, there is a guy in ATLBIMMERS with (12) new f8x driveshafts for sale in Cumming. 750 obo