XClutch Twin Disc Review & Installation (6MT N54)

martymil

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Sep 6, 2017
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So basically the metal tob is causing the middle disc to make noise but doesn't with the oem bearing ?

They both do the exact same thing push the diaphragm in and nothing else.
 

The Convert

Captain
Jun 4, 2017
1,011
So basically the metal tob is causing the middle disc to make noise but doesn't with the oem bearing ?

They both do the exact same thing push the diaphragm in and nothing else.
They’re not saying that. They’re saying specifically that the TOB is not the cause of the noise, and that the noise is coming from the middle plate.

I could see the metal TOB being a better transmitter for getting the sound of the middle plate into the cabin though.
 

The Convert

Captain
Jun 4, 2017
1,011
not saying you did, asking a question as I haven't seen one use the higher lobe, must be a US setup difference.
Not sure. I remember it being a thing back when the twin discs came out and some people used high setting and some low. There was a big debate and it turned out some people were high from factory, while others low. I can’t for the life of me remember why they varied though.
 
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martymil

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Sep 6, 2017
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So the metal tob is causing a nvh transfer from the middle disc but doesn't happen with the oem one.

So at the end of the day the metal TOB is the root of the problem by allowing NVH from the middle disc to be transferred.
 

The Convert

Captain
Jun 4, 2017
1,011
So the metal tob is causing a nvh transfer from the middle disc but doesn't happen with the oem one.
If I had to guess, that would be it.

When the clutch pedal is depressed, the TOB makes contact with the clutch release fork and pressure plate, and the middle plate is free to slip/rattle/vibrate inside the pressure plate cage. So, the metal TOB creates a full path of metal objects for the sound to travel right up into the cabin through the shifter.

Although, I don’t think my spec twin disc had that whirring with the pedal depressed when I had the aluminum TOB installed. Maybe it’s unique to the cage design or the size of the gap between the middle plate and cage?
 

GGMR2T

Private
May 31, 2018
46
Had a break in the weather yesterday and had a chance to take the car for a rip, so I thought I'd update with the fluid change results thus far. After getting the gearbox up to temp, I did notice a slight reduction in the noise at idle, probably 15-20% quieter. But where I really noticed a significant reduction in noise is during that low rpm/high load (lugging) area. It was quite loud before to where I'd shift down if I was below like 3500rpm. That has virtually disappeared. Much more drive-able now. I can't comment on changes in shifting, other than normal light driving and it seems no different. Possibly slightly smoother, but where it will really matter to me (once the clutch is broken in of course) is ripping through the gears with hopefully no grinding or "wall hitting". HTH!
 

martymil

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Sep 6, 2017
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Ok guys i'm going to share something with you which will greatly help reduce nvh in your car especially with twin plates.

What I found that if you have less than stellar down pipe fitment whilst using a standard or similar exhaust you will get excessive nvh in high load low rpm.

To get rid of it you either get an aftermarket exhaust with multiple slip joints to relive the tension or weld it flex joints like this between the bracket that holds the exhaust up next to the gearbox and the dp.

This will greatly reduce nvh, that's why the factory dp's had them.


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GreyNBlueE92

Specialist
Oct 3, 2018
88
OH
Ok guys i'm going to share something with you which will greatly help reduce nvh in your car especially with twin plates.

What I found that if you have less than stellar down pipe fitment whilst using a standard or similar exhaust you will get excessive nvh in high load low rpm.

To get rid of it you either get an aftermarket exhaust with multiple slip joints to relive the tension or weld it flex joints like this between the bracket that holds the exhaust up next to the gearbox and the dp.

This will greatly reduce nvh, that's why the factory dp's had them.


View attachment 27384
What engine/trans mounts are you running? Do you think stiff mounts would eliminate the need for a flex section?
 

GreyNBlueE92

Specialist
Oct 3, 2018
88
OH
My thought was if someone had soft mounts with a rigid exhaust it might transmit more noise than rigid mounts with rigid exhaust or vice versa
 

martymil

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Sep 6, 2017
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I run stock 1m mounts, since swapping to an aftermarket mids with multiple slip joints and taking the tension of the dp's it has reduced nvh by a min 50 %

I'm looking to install these aswell as these will help even more with the nvh after installing a set of these on a mates car but he has a stock mid pipe.
 
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fmorelli

Colonel
Staff member
Aug 11, 2017
2,214
Virginia
The stiffer the trans mount, the more NVH transmission into the cabin. Same as with stiffer motor mounts.
I would add two observations. First off trans mounts are worse than motor mounts in this regard, in my experience. On this car one can get away with Revshift 80a on the motor, but no way I'd put poly mounts on the trans. That said the trans answer is simple - Rogue Engineering cylindrical rubber mounts, and install AKG deflection cups if you feel the need. No NVH increase with the RE trans mounts and much beefier than stock. If only we could score the same on the motor mounts but, for now, Revshift 80a seems like the only viable alternative.

Filippo
 

The Convert

Captain
Jun 4, 2017
1,011
I would add two observations. First off trans mounts are worse than motor mounts in this regard, in my experience. On this car one can get away with Revshift 80a on the motor, but no way I'd put poly mounts on the trans. That said the trans answer is simple - Rogue Engineering cylindrical rubber mounts, and install AKG deflection cups if you feel the need. No NVH increase with the RE trans mounts and much beefier than stock. If only we could score the same on the motor mounts but, for now, Revshift 80a seems like the only viable alternative.

Filippo
With the stock dmfw and solid aluminum trans and motor mounts, I had very minimal added NVH. As soon as I got rid of the dmfw, however, the NVH was unbearable and the clutch was engagement was absolutely horrendous. After switching back to oem mounts, the NVH quieted down a good bit, and the clutch got better, but is still no bueno for a DD.
 

GreyNBlueE92

Specialist
Oct 3, 2018
88
OH
With the stock dmfw and solid aluminum trans and motor mounts, I had very minimal added NVH. As soon as I got rid of the dmfw, however, the NVH was unbearable and the clutch was engagement was absolutely horrendous. After switching back to oem mounts, the NVH quieted down a good bit, and the clutch got better, but is still no bueno for a DD.
Did you have a flex section in exhaust then?
 

martymil

Lieutenant
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Sep 6, 2017
919
Down Under
Most of the high load low rpm vibration is due to the exhaust and when mated with this clutch and slip joints or flex joints is almost non existent.

Its a cheap fix some of you guys that might want to try before you start changing engine and gearbox mounts and go from there.
 

The Convert

Captain
Jun 4, 2017
1,011
Did you have a flex section in exhaust then?
Yes. The motiv kits all come with a flex section integrated into the down pipe.

Most of the high load low rpm vibration is due to the exhaust and when mated with this clutch and slip joints or flex joints is almost non existent.

Its a cheap fix some of you guys that might want to try before you start changing engine and gearbox mounts and go from there.
This is only a small part of it. My exhaust has always had a flex section in the down pipe, and transmission mounts made a big NVH difference. I’ve also had the exhaust mounted to the transmission like oem and run it without that mount. Thicker gear oil will also quiet down the gear clatter of the transmission some. I’ve also used both tail shaft flex discs with no noticeable change between the two. Motor mounts made a big clutch engagement difference. I have attacked this, as well as many others, from every angle and every component.

If you want to get rid of as much NVH as possible, use thicker fluid to damp the gear clatter, oem trans and motor mounts to damp the vibration transmission into the chassis, and raise your engine idle to get out of the low rpm range that seems to be hitting a resonant frequency of the motor/trans.
 
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GGMR2T

Private
May 31, 2018
46
Most of the high load low rpm vibration is due to the exhaust and when mated with this clutch and slip joints or flex joints is almost non existent.

Its a cheap fix some of you guys that might want to try before you start changing engine and gearbox mounts and go from there.
For some reason I never realized the stock DP had that flex section. Probably because it's still pretty stiff but does absorb/allow some flex? I think if nothing else, they will allow enough adjustment to eliminate the pesky leaks at the DP/exhaust connection that are hard to get rid of without perfect fitment, Which I seem to never achieve haha! Worth a shot in both regards for me.
 

martymil

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Sep 6, 2017
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I have minimal to next to no nvh in high load low rpm situations but I run stock bushes, stock mounts and factory oil with a full titanium akrapovic exhaust, akra in their infinite wisdom put flex joints in their dp but they are tiny compared to AR design

Even though they are near a perfect fit still need some kind of flex joint to relive fitment situations.

When I ran the stock mids they where horrible and definitely need some kind of flex joint.

GGMR2T try the flex joint on both your mids and you will be pleasantly surprised how much better the fitment gets and lowers the nvh.

Not saying it will get rid of all as there is to many variables in most peoples setups but it did in mine and will definitely help a lot in most.
 
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