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Discussion Starter #1 (Edited)
Just pulled the trigger on a DSS Carbon Fiber Driveshaft.

Any personal experiences with this one? I've read a lot of favorable experiences with people saying it's one of their favorite modifications as it really changes a lot with driveability and responsiveness.

I confirmed when ordering you do have to drill larger holes for the 10 mm bolts supplied to bolt at the rear diff flange. The stock bolts are 8 mm so the only way to bolt the CF driveshaft is by enlarging the holes. I guess reversability wouldn't be necessarily easy if you wanted to revert back to stock, but I don't plan on selling my car anytime soon, or ever, so I guess it becomes a moot point.

Really excited, looking forward to getting this sucker on.

**UPDATE**

Finally had some free time this morning to install the DSS Carbon Fiber Driveshaft. Just wanted to give my thoughts and opinions on installation and the driving experience.

Here are some photos during installation:

Stock driveshaft


DSS CF Driveshaft


Very small (insignificant?) difference in DSS flange (10 mm holes) and rear diff flange (8 mm holes)


DSS CF bolted to rear diff with stock hardware






Transmission yoke end of the driveshaft


Thoughts/Impressions:

Installation-wise I think this was fairly easy. Took me about 1 and 1/2 hours from start to finish and I was going slow to make sure I didn't screw anything up. I reused stock hardware (at least for now) so that in the off-chance something didn't jive right with my car I could revert back to stock with no issues. There is obviously a very small (~1 mm on either side) gap on the DSS flange side where the stock bolts don't make contact with the hole edges being that the flange has 10 mm holes and stock bolts are 8 mm. But, the middle of the driveshaft flange seats onto the center of the rear diff via a small lip so everything is centered with no slack from the get-go. I guess the end user assumes the risk and repercussions of not drilling out larger holes for the supplied 10 mm hardware by DSS. However, I would venture to say you shouldn't experience any issues down the road as I've heard from many people that reused stock hardware with no issues to date. YMMV. I don't think I'd notice a difference in feel if I drilled out larger holes, though I was ready, drill in hand, to bore out larger holes and decided against it, for now.

With regards to impressions on driveability. As of right now, I have only driven for a short period of time on main roads and a little highway time. I have taken the car up to about 90 mph and have not yet experienced any resonance or vibrations, so that is a plus. As far as wow-factor, I'd be hard pressed to say I'm thoroughly impressed. While the shaft is lighter and 1-piece, I wasn't taken back by any monumental changes to driving feel. Unless my butt dyno isn't as sensitive as others, I can say I didn't notice that much of a difference in driveability, at least not $1000-worth. Yes, there may be a little less driveshaft play in between shifts, but nothing that is going to blow you out of your seat. You notice a little less bucking from throttle input and slightly smoother transition when letting go of the gas and decelerating, but nothing extraordinary. Honestly, I was thinking to myself while driving if I were to test drive the car not knowing the CF driveshaft was there, if I would even notice a difference in driveability. Maybe? Maybe not.

It's hard to say having only had a little time behind the wheel. I will say though, that some people's reviews of the product are way over-hyped or at least they've got some super sensitive butt dynos. There definitely isn't a 100% decrease in drivetrain slack, contrary to some opinions I've read saying all bucking between shifts is gone. Yes there is a driver component to it and how well you finesse your shifts. But even before installation of a CF driveshaft, you could manage to have smooth transitions between shifts with minimal to no bucking if you wanted to . Keeping driver input constant, I would cautiously say the change in driveability is satisfactory at best. I would have to definitely think long and hard about the cost/benefit ratio if I had to purchase again knowing everything I know now. Maybe swapping out transmission/motor mounts and/or bushings would add to the overall change in feel. Then again, you wouldn't be able to say the change in driveability was all due to the CF driveshaft.

I will continue to analyze my driving experience in the coming weeks, maybe it's a change that will become more apparent in different driving situations. Hopefully, this helps some people considering making such a big purchase. I can't say it isn't worth it as I haven't given myself sufficient time behind the wheel to properly analyze every aspect of the driving experience. However, I'm a little skeptical to see where there could possibly be any room for change in feel.

Anyways, I'll try to update this again in the coming weeks if I deem it necessary. For now, I'm going to go wash my car; a car definitely feels better after giving it a good wash ;) :lol:.
 

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I'd say it was worth it. Low speed bucking/lurching is anything but gone however... :( I reused stock hardware. Didn't feel like drilling into the flange.
 

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Discussion Starter #3
I'd say it was worth it. Low speed bucking/lurching is anything but gone however... :( I reused stock hardware. Didn't feel like drilling into the flange.
Almost every review I read said that bucking/lurching was eliminated. Do you think it has anything to do with reusing stock hardware? I'm under the impression that the flanged end on the drive shaft has 10 mm holes. So if you're putting 8 mm bolts through it, it might not be creating a good fit.
I was going to ask how you managed to fit stock hardware. I made sure to ask when ordering and it didn't seem like drilling the flanges was optional.
 

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Almost every review I read said that bucking/lurching was eliminated. Do you think it has anything to do with reusing stock hardware? I'm under the impression that the flanged end on the drive shaft has 10 mm holes. So if you're putting 8 mm bolts through it, it might not be creating a good fit.
I was going to ask how you managed to fit stock hardware. I made sure to ask when ordering and it didn't seem like drilling the flanges was optional.
Its possible, but I'm not sure that the hardware would make that drastic a difference. Hopefully someone else can chime in on this. I'd like to get rid of the bucking and hopefully there isn't something else mechanically wrong with the car.
 

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Absolutely the best drive ability mod you can do. Especially if you drive in any bit if traffic. It's fantastic. You can resuse the stock hardware no problem. In fact mine didn't come with any hardware at all. It's perfectly fine. You'll love it and think you have a different car!
 

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Love mine...no issues bolting up with stock hardware. It has a raised lip that seats in the rear diff yoke and then it is bolted tight so no misalignment.
 

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Except cost, there is no downside to the DSS. If your car needs a drive shaft its a no brainer. But anyone who believes this is their best mod either has no other mods, or has made especially poor choices. It's a lot of money for a small difference. If you done most everything else, its a nice finishing touch. Yes I've driven one since they first came out - a two or three years.
 

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Discussion Starter #9
Absolutely the best drive ability mod you can do. Especially if you drive in any bit if traffic. It's fantastic. You can resuse the stock hardware no problem. In fact mine didn't come with any hardware at all. It's perfectly fine. You'll love it and think you have a different car!
Love mine...no issues bolting up with stock hardware. It has a raised lip that seats in the rear diff yoke and then it is bolted tight so no misalignment.
So I specifically asked when buying and the guy confirmed you would have to drill out a larger hole; maybe I'll call again tomorrow and try confirming with someone else there. Did your driveshafts come drilled with 8 mm holes or did it come with the 10 mm holes and you used the OEM 8 mm bolts through it with no problem? I'm having trouble visualizing how that would work since you would have that hollow space within the flange thickness of where the bolt isn't making direct contact. I assume this would lead to instability and probably wouldn't be safe? Or can you ask them to specifically drill 8 mm holes at the flange? Sorry I'd rather have it be plug and play, but it seems I'm reading mixed reviews where some people such as the thread linked above a guy added a modified spacer around the 8 mm bolt so that it fit the 10 mm hole on the flange?

Please also note I want to confirm this for the DSS driveshaft specifically, I don't know if other brands make it so you don't have to drill anything extra out.
 

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I was not supplied any extra hardware. I used stock hardware. It was years ago, but there was nothing that looked like it would be an issue. Don't know if DSS or Subie has changed anything since then - mine is on an 05.
 

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I have a DSS CF shaft...

Different size bolts? :confused: Not sure who you talked to, but it was a direct swap in and the stock bolts fit with no issue. I have no issues, no bad fitment, no vibrations or anything. Also, while the low speed "bucking" has been reduced, a lot of that comes down to finessing the clutch when taking off, with smooth throttle inputs. Driving an STi smoothly takes some diligence on one's part :) I find that if I'm lazy in any way on the shifting, the car will let me know.

If you still have vibrations at higher speeds, the DS could be out of balance. They say to rotate it 90 degrees and test. If that doesn't help, you send it back.

Except cost, there is no downside to the DSS. If your car needs a drive shaft its a no brainer. But anyone who believes this is their best mod either has no other mods, or has made especially poor choices. It's a lot of money for a small difference. If you done most everything else, its a nice finishing touch. Yes I've driven since they first came out - a few two or three years.
I'd agree that the CF DS isn't a "top of the list" mod. It's expensive as hell for a little smoother drive at low speed. It's nice, don't get me wrong, but I'd do a number of other mods before recommending one. Such as:

- 2015 steering rack
- Stumble fix
- GOOD Protune: this makes more difference in smooth driving than a CF DS
- Lighter weight wheels
- Engine mounts/pitch stop/trans bushings
- Shifter bushings and short shifter
 

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Ya I have installed two of them (one on my friends and my own) and we just reused the stock hardware and neither of us have had any issues.

As for my comment on best mod - please go back and look at the defining word I said - I said best DRIVEABILITY mod. Overall it would not be on the top of my list BUT If you are DD your car and are consistently in heavy traffic for your commute - its well worth every single penny.

If I wasn't in traffic every day - then I would notice it less and probably wouldn't care all that much. But I tend to spend the majority of my commute home in its most noticeable power and driving range.

Also - ditto on the finessing the clutch. I do occasionally get some bucking but as you stated - Its when you are being lazy - the car will let you know.

Basically - I have never met a single person who regretted the DSS once it was installed. Also the install is a piece of cake and takes 20-30 minutes if you study what you have to do and are somewhat mechanically inclined.
 

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Also - ditto on the finessing the clutch. I do occasionally get some bucking but as you stated - Its when you are being lazy - the car will let you know.
If someone is have problems driving the car, a CF DS isn't going to cure it.
They need to learn how to drive the car. Might it help? Perhaps a bit.

Basically - I have never met a single person who regretted the DSS once it was installed. Also the install is a piece of cake and takes 20-30 minutes if you study what you have to do and are somewhat mechanically inclined.
Completely agree here except it took a bit longer - not long, but longer.
Takes me 20 min to jack the car and secure it.
I only did mine cause long ago a dealer told me I needed a new drive shaft. Rather than pay $800 for them to install a stock DS, I did the CF myself. The dealer was probably wrong. But As BJJMark95 wrote - I still don't regret it. It's an improvement in NVH, and a small performance enhancement - just significantly noticeable.
 

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As for my comment on best mod - please go back and look at the defining word I said - I said best DRIVEABILITY mod. Overall it would not be on the top of my list BUT If you are DD your car and are consistently in heavy traffic for your commute - its well worth every single penny.

If I wasn't in traffic every day - then I would notice it less and probably wouldn't care all that much. But I tend to spend the majority of my commute home in its most noticeable power and driving range.
Totally, it makes low gear driving a much easier affair. When I drive my gf's WRX, it's a heavy handed experience. While it drives smooth, it takes more effort for the car to pick up momentum, and more effort to bleed it off (in stop/go traffic) when you aren't leaving 1st gear. With the CF DS in my car, the revs build smoother and with less effort, and the reduced mass when engine braking lets the car slow down smoother.

I've recently added a lightened crank pulley, and the car is now even better in the driveability department. I can drive lazy sometimes and it's more forgiving :lol:
 

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I have both the lightweight pulley and the DSS - awesome sauce but I dont think the pulley plays much in that.

The only other driveability mod I would argue is up there with the DSS is my DAMD wheel cuz I get to put my hands all over it everytime I drive... :D

And you're correct - there were 3 of us doing the work when we did it. One handing us the parts, and 2 under the car doing the positioning. Suppose that makes a difference hahahaha.
 

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+1 on the DAMD wheel. Amazing.

I guess I should have been more specific. I realize the STI is not a "smooth" car by nature, but I was expecting the off throttle bucking to be completely eliminated. Other than that every other pro listed is :tup:
 

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FWIW I'm running a ACT streetlight - a marginally lighter flywheel. It's a bigger difference than the drive shaft, far bigger difference than pulley I'm sure. Another noticeable but not night and day performance enhancement.

Unlike the drive shaft it does have the downside that it take s few more revs to get moving. It's fine here in the flatlands of SJ. I wouldn't recommend it to anyone who regularly travels big hills or mountains. Adds character to my ridiculously harsh GD :) I feather at most starts Vvrrhh . . Vvrrhh . .Vvrrhhh o o m m . .

It would drive many here crazy :) :) :)
 

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Discussion Starter #20
I have a DSS CF shaft...

Different size bolts? :confused: Not sure who you talked to, but it was a direct swap in and the stock bolts fit with no issue. I have no issues, no bad fitment, no vibrations or anything. Also, while the low speed "bucking" has been reduced, a lot of that comes down to finessing the clutch when taking off, with smooth throttle inputs. Driving an STi smoothly takes some diligence on one's part :) I find that if I'm lazy in any way on the shifting, the car will let me know.

If you still have vibrations at higher speeds, the DS could be out of balance. They say to rotate it 90 degrees and test. If that doesn't help, you send it back.



I'd agree that the CF DS isn't a "top of the list" mod. It's expensive as hell for a little smoother drive at low speed. It's nice, don't get me wrong, but I'd do a number of other mods before recommending one. Such as:

- 2015 steering rack
- Stumble fix
- GOOD Protune: this makes more difference in smooth driving than a CF DS
- Lighter weight wheels
- Engine mounts/pitch stop/trans bushings
- Shifter bushings and short shifter
Ya I have installed two of them (one on my friends and my own) and we just reused the stock hardware and neither of us have had any issues.

As for my comment on best mod - please go back and look at the defining word I said - I said best DRIVEABILITY mod. Overall it would not be on the top of my list BUT If you are DD your car and are consistently in heavy traffic for your commute - its well worth every single penny.

If I wasn't in traffic every day - then I would notice it less and probably wouldn't care all that much. But I tend to spend the majority of my commute home in its most noticeable power and driving range.

Also - ditto on the finessing the clutch. I do occasionally get some bucking but as you stated - Its when you are being lazy - the car will let you know.

Basically - I have never met a single person who regretted the DSS once it was installed. Also the install is a piece of cake and takes 20-30 minutes if you study what you have to do and are somewhat mechanically inclined.
Yeah, I mean I called again today a 2nd time and asked for technical support. Again, I got the answer that you need to drill the bolts holes larger. If I call anymore they're gonna start recognizing me as the crazy guy who keeps calling about the same thing. Unless you guys got yours years ago and something is different now. Feel free to call yourself, but I'm not mistaken. It even mentions on the website that modification will be required for the supplied 10 mm bolts in the description. They said if people are reusing stock hardware they're doing it at their own risk.

If you can confirm one thing for me at least, when reusing stock hardware, the holes on the driveshaft, are they at least bigger? Meaning do they look like 10 mm bolts would go through them, but you fit the 8 mm through anyway?
 
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