F8X M3/M4 CF Drive shaft mod

[Projecte46m3]

Food for thought: driveshaft is vibration free up to 8k RPM in 1st, 2nd, 3rd gear. It only vibrated at 80 mph in 6th gear and it was around 3k RPM the other night. Will test further. If it was the driveshaft wouldn't it vibrate at high RPM in any gear?

I was thinking this as well.

[EthanolTurbo]

Food for thought: driveshaft is vibration free up to 8k RPM in 1st, 2nd, 3rd gear. It only vibrated at 80 mph in 6th gear and it was around 3k RPM the other night. Will test further. If it was the driveshaft wouldn't it vibrate at high RPM in any gear?

[0-60motorsports]

They said a 3-4 day turnaround. I have to work on sending them the specifics to get pricing. A rebuild used to go for $600-ish plus $150 to modify plus core charge. They don't have to replace the u-joints or center bearing. If I had to take a wild guess...$500 to weld the end on and balance? Its not hard...they usually turn a modify and rebuild around the same day.

Alright buddy I'll give you a call soon.

[bigjae46]

Thanks for the detailed info here regarding balancing your shaft LOL.

All kidding aside I'll call you in a day or two to decide as I know a few places I can get the DS from too. It'll all come down to budget for me. Thanks brother

They said a 3-4 day turnaround. I have to work on sending them the specifics to get pricing. A rebuild used to go for $600-ish plus $150 to modify plus core charge. They don't have to replace the u-joints or center bearing. If I had to take a wild guess...$500 to weld the end on and balance? Its not hard...they usually turn a modify and rebuild around the same day.

[liam821]

Looks like you can still buy these new from BMW for about $750 or so. Search for 26109882181.

[0-60motorsports]

I might have a solution through Powertrain Industries.

I believe that there are only a couple of rebuilders that can dynamically balance a driveshaft. Which makes sense because the equipment is large, expensive, and specific to balancing long shafts (lol), likely would need to balance thousands of shafts of break even. Think two large precision lathes end to end. I believe Powertrain Industries has a proprietary setup. Or at least that what I can remember from the sales pitch they gave me years ago.

I have an account with them and have facilitated over 30 rebuilds, some include modified driveshafts for 5 speed conversions. I have not had one complaint of a vibration issue that wasn't there before. I was going to go this route if 0-60 Motorsports wanted to enlist my assistance. I think this would be a straightforward modification for them. Likely can get it done at the same or lower cost that what I've seen here.

I will say Powertrain Industries uses non-OE parts. The issue, for me, has been the CV boot and the center bearing that they use. I did supply an OEM part for a couple of rebuilds. Then god help you if you move the CV joint at all...massive amounts of grease will come out. They overstuff the CV boot with grease. The driveshaft itself has been vibration free 6 years later and lots of track time.

Thanks for the detailed info here regarding balancing your shaft LOL.

All kidding aside I'll call you in a day or two to decide as I know a few places I can get the DS from too. It'll all come down to budget for me. Thanks brother

[bigjae46]

I might have a solution through Powertrain Industries.

I believe that there are only a couple of rebuilders that can dynamically balance a driveshaft. Which makes sense because the equipment is large, expensive, and specific to balancing long shafts (lol), likely would need to balance thousands of shafts of break even. Think two large precision lathes end to end. I believe Powertrain Industries has a proprietary setup. Or at least that what I can remember from the sales pitch they gave me years ago.

I have an account with them and have facilitated over 30 rebuilds, some include modified driveshafts for 5 speed conversions. I have not had one complaint of a vibration issue that wasn't there before. I was going to go this route if 0-60 Motorsports wanted to enlist my assistance. I think this would be a straightforward modification for them. Likely can get it done at the same or lower cost that what I've seen here.

I will say Powertrain Industries uses non-OE parts. The issue, for me, has been the CV boot and the center bearing that they use. I did supply an OEM part for a couple of rebuilds. Then god help you if you move the CV joint at all...massive amounts of grease will come out. They overstuff the CV boot with grease. The driveshaft itself has been vibration free 6 years later and lots of track time.

[Slideways]

That's unfortunate. Hopefully Altaran has better luck with the one he built.

[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.