F8X M3/M4 CF Drive shaft mod

[EthanolTurbo]

Just double checking, only the diff end needs to modified? The shop is thinking the transmission end also needs modification.

You have to do both ends.

[x Spades x]

I just read this whole thread and got excited... then disappointed... then excited again.

I have an SMG car, so very interested in seeing if this is possible. Should I buy a CF driveshaft??

[Radekxpl]

Just double checking, only the diff end needs to modified? The shop is thinking the transmission end also needs modification.

Although transmission side looks the same to the untrained eye, but if you closely the Gibo is larger on f8x then on the e46 therefore won't fit so you would need to do transmission side as well from my understanding 🤷♂️


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[bigjae46]

Just double checking, only the diff end needs to modified? The shop is thinking the transmission end also needs modification.

[0-60motorsports]

Any more updates from others who have done this? Any one know a shop on Jax FL who can do the work?

[Projecte46m3]

Can we share a list of good shops that are able to handle the modification?

[liam821]

There you have it. My driveshaft was done improperly. Now I have to figure out why.

That is so frustrating. What a pain in the ass

[SliM3]

There you have it. My driveshaft was done improperly. Now I have to figure out why.

I was wondering why your shop welded a new tri-flange to your DS. IMO when going that route they should've at least used the output flange from your transmission to ensure the DS centerline stays aligned with the transmission output shaft centerline.


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[EthanolTurbo]

So, I finally got around to a longer drive with my car.

As for my CF Shaft, there are no downsides I could feel.

The car does feel much more direct, however I am driving a freshly rebuild and more powerful engine, so I am not fully attributing that to the shaft.

No more clunking. I did have quite a bit before and I have not done any changes to the tranny or diff since. So that's a plus.

Due to prior feedback above I also did some runs above 130kph/80mph. No vibrations.

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There you have it. My driveshaft was done improperly. Now I have to figure out why.

[Altaran]

One more thing which may be relevant:
All my drivetrain components are running stiffer mounts that stock so there is a lot less movement.

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[Altaran]

So, I finally got around to a longer drive with my car.

As for my CF Shaft, there are no downsides I could feel.

The car does feel much more direct, however I am driving a freshly rebuild and more powerful engine, so I am not fully attributing that to the shaft.

No more clunking. I did have quite a bit before and I have not done any changes to the tranny or diff since. So that's a plus.

Due to prior feedback above I also did some runs above 130kph/80mph. No vibrations.

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[discoelk]

FWIW, I understand what you are saying. 3rd/8000 is a faster wheel/driveshaft speed than 6th/80mph. 3rd/8000 is closer to 100mph. In my limited experience, discerning drivetrain vibration at high engine speed and hard acceleration is difficult butEthanolTurbo would need to elaborate.

[Radekxpl]

Another twist, if you are in 3rd gear at 7600 rpm at 80mph and then put the car in neutral and coast, does drive shaft stop spinning or even start spinning slower at idle vs 7600 while you are still traveling at 80mph?

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Driveshaft does not stop spinning if you put car in neutral at any speed whether you going 80mph or 20mph it will continue spinning. That I know for a fact.
Which now I think about it 🤔🤦what Discoelk said makes sense is directly related to wheels speed, however it still doesn’t explain no vibrations at 80 in 3rd gear and vibrations 80mph in 6th gears since drive shaft would be spinning at the same rate no matter what gear.

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[mrgizmo04]

Another twist, if you are in 3rd gear at 7600 rpm at 80mph and then put the car in neutral and coast, does drive shaft stop spinning or even start spinning slower at idle vs 7600 while you are still traveling at 80mph?

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[Radekxpl]

Driveshaft speed is directly correlated to wheel speed. Engine speed and gear do not matter. The shaft (heh) sounds out of balance or as someone else mentioned, the flanges are not welded true (misalignment issue).

Even given what your saying is correct that still does not add up since this would mean going 80mph in 3rd gear would result same driveshaft rpm speed as going 80mph in 6th gear, given what our Tester has mentioned is true, that there was no vibration at 8k engine rpm in 1st 2nd, 3rd gears emphasis on the 3rd gear here since m3 in 3rd gear is doing well over 80mph close to redline 8k. This just proves Something it's not adding up here.


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