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Old 06-16-2021, 11:14 PM   #1
jeepmor
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Bucking after new clutch install

I had a stage 2 SouthBend clutch installed a few months ago after the TOB failed. This is an Exedy clutch with 6 segments of their Feramic compound.

14 FRS at 87k manual trans car for reference. Put all new parts in down to a cerakoted bearing retainer, Verus fork and new subie TOB and flywheel. Only part I didn’t replace is the clutch pivot boss if I missed something.

Since then I can get some nasty bucking if trying to launch hard. It gets worse when after spirited driving for a good session. It’s tamed a bit since installation, but still occasionally it gets obnoxious. I was thinking it was break in norms, but it it has not stopped yet.

Also, I did have a Whiteline trans mount bushing installed. And lately, an HKS supercharger which has shown me how soft the bushing package really is making the issue more prevalent.

Now, to the solution space. I’m not sure if this is the engine/trans mount set or the rear end suspension bits. Any comments appreciated as to where to start. Which might just be buying a GoPro to see the problem.

My car is stock suspension wise other than the Whiteline trans bushing. I’d prefer an STI parts solution, but not sure if they address the rear end bushings with different parts like the STI grade engine and trans mounts.
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Old 06-17-2021, 12:18 AM   #2
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Originally Posted by jeepmor View Post
I had a stage 2 SouthBend clutch installed a few months ago after the TOB failed. This is an Exedy clutch with 6 segments of their Feramic compound.

14 FRS at 87k manual trans car for reference. Put all new parts in down to a cerakoted bearing retainer, Verus fork and new subie TOB and flywheel. Only part I didn’t replace is the clutch pivot boss if I missed something.

Since then I can get some nasty bucking if trying to launch hard. It gets worse when after spirited driving for a good session. It’s tamed a bit since installation, but still occasionally it gets obnoxious. I was thinking it was break in norms, but it it has not stopped yet.

Also, I did have a Whiteline trans mount bushing installed. And lately, an HKS supercharger which has shown me how soft the bushing package really is making the issue more prevalent.

Now, to the solution space. I’m not sure if this is the engine/trans mount set or the rear end suspension bits. Any comments appreciated as to where to start. Which might just be buying a GoPro to see the problem.

My car is stock suspension wise other than the Whiteline trans bushing. I’d prefer an STI parts solution, but not sure if they address the rear end bushings with different parts like the STI grade engine and trans mounts.
Nasty "bucking"?

Please describe "bucking" in reference to an automobile?

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Old 06-17-2021, 12:40 AM   #3
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Clutch chatter. Stock clutch is rated to let go before the transmission frags, and engages smoothly.
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Old 06-17-2021, 03:53 PM   #4
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Nasty "bucking"?

Please describe "bucking" in reference to an automobile?
Feels like wheel hop on a leaf spring suspension. It is clutch chatter of some sort, just expected it to wear in by now and go away. The feeling from the driver's seat is that the tailshaft of the trans is moving, or the rear suspension connection to the unibody is bucking to and fro its range of motion.

It is a 350 ft-lb clutch.
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Old 06-18-2021, 09:45 PM   #5
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So on one drive I purposely gave it a lot of clutch slip a few times to wear it in a bit more. Not obnoxious, just a few slow engagements making it slip a lot. It is improving the 1st gear takeoffs.

This clutch doesn't make it easy. Feels the same weight wise to the leg, but engages like rock compared to stock. Learning curve on the break in, I think I'll be fine in another month or so of commuting.

Last edited by jeepmor; 06-19-2021 at 11:48 PM.
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Old 06-25-2021, 01:36 PM   #6
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Quote:
Originally Posted by jeepmor View Post
I had a stage 2 SouthBend clutch installed a few months ago after the TOB failed. This is an Exedy clutch with 6 segments of their Feramic compound.



14 FRS at 87k manual trans car for reference. Put all new parts in down to a cerakoted bearing retainer, Verus fork and new subie TOB and flywheel. Only part I didn’t replace is the clutch pivot boss if I missed something.



Since then I can get some nasty bucking if trying to launch hard. It gets worse when after spirited driving for a good session. It’s tamed a bit since installation, but still occasionally it gets obnoxious. I was thinking it was break in norms, but it it has not stopped yet.



Also, I did have a Whiteline trans mount bushing installed. And lately, an HKS supercharger which has shown me how soft the bushing package really is making the issue more prevalent.



Now, to the solution space. I’m not sure if this is the engine/trans mount set or the rear end suspension bits. Any comments appreciated as to where to start. Which might just be buying a GoPro to see the problem.



My car is stock suspension wise other than the Whiteline trans bushing. I’d prefer an STI parts solution, but not sure if they address the rear end bushings with different parts like the STI grade engine and trans mounts.
It's the Whiteline trans mount 100% I had the stage 2 sb clutch in prior to doing the mount and Perrin insert. Take offs are still smooth but I do get some low speed bucking in 1st gear. Never had that before. So guessing that's what your feeling. Clutch feels OEM and take off is the same for me

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Old 06-30-2021, 10:57 PM   #7
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It's the Whiteline trans mount 100% I had the stage 2 sb clutch in prior to doing the mount and Perrin insert. Take offs are still smooth but I do get some low speed bucking in 1st gear. Never had that before. So guessing that's what your feeling. Clutch feels OEM and take off is the same for me

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I had my suspicions, I'll have to yank it and test again to be sure. I have slipped the clutch a bit figuring I was having a long break in as I'm pretty easy on clutches. But I never felt any shuddering that way, just first gear or reverse when trying to be brisk on take offs.
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Old 06-30-2021, 11:00 PM   #8
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Originally Posted by jflogerzi View Post
It's the Whiteline trans mount 100% I had the stage 2 sb clutch in prior to doing the mount and Perrin insert. Take offs are still smooth but I do get some low speed bucking in 1st gear. Never had that before. So guessing that's what your feeling. Clutch feels OEM and take off is the same for me

Sent from my GM1915 using Tapatalk
I had my suspicions, I'll have to yank it and test again to be sure. I have slipped the clutch a bit figuring I was having a long break in as I'm pretty easy on clutches. But I never felt any shuddering that way, just first gear or reverse when trying to be brisk on take offs. The bushings on this car seem really soft, I'm considering some STI bits.
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Old 06-30-2021, 11:06 PM   #9
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Originally Posted by jeepmor View Post
I had my suspicions, I'll have to yank it and test again to be sure. I have slipped the clutch a bit figuring I was having a long break in as I'm pretty easy on clutches. But I never felt any shuddering that way, just first gear or reverse when trying to be brisk on take offs. The bushings on this car seem really soft, I'm considering some STI bits.
Go with the STI n-group stuff. I have gotten used to my Whiteline+Perrin mount. It seems to have broken in but the bucking is there from time to time in low speed first gear driving.

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Old 07-01-2021, 12:36 PM   #10
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@jeepmor you might need the whiteline positive traction kit (subframe and differential bushing) to stiffen the rear. IMO it makes my car much easier to drive at low rpm, can lug the engine and the (stock) clutch doesn't make a peep on my 130k mile car. Though will make the car stiffer than coilovers and very loud and sometimes you'll get noisy vibrations from the rear.


I also notice that the clutch might act differently after some heat has gotten into the clutch or bushings. Maybe more deflection, compliance, etc.
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Old 07-01-2021, 10:41 PM   #11
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Was thinking I was all alone with this issue. I'm getting used to it as well and it has greatly reduced. I definitely put a large bit of that on breaking in the clutch. 350 ftlb of holding power is a lot more than stock, and when it bites, there is zero slip. My new routine of slipping the clutch on purpose is in 6th gear going 60ish. Not tortuous, just making it slip a bit, run a few miles to let it coole, slip it again routine. This helped a lot more than trying to do it in lower gears.

That said, It hasn't disappeared just yet, but I'm adapting well and not as concerned about it now. Pretty new to sports car stuff like this, but an old hat in regards to my jeep. And, now that I've driven enough, it's very similar in nature to wheel hop on the jeep leaf springs.

Thanks for the STI parts reference and Whiteline rear bushing suggestions. I've read the STI parts are stiffer, but still have low NVH. Not thrilled about the NVH feedback from radroach, but good to know it addresses a lot of this issue. It always felt like it was in the back end, not the clutch, but this type of issue can be difficult to pinpoint.

As stated before, it really feels like leaf spring wheel hop.
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Old 12-04-2022, 08:20 PM   #12
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I had the clutch opened back up recently, this root cause was the Verus fork with sloppy tolerances. The shop put in an OEM fork and all is well again, no more serious bucking.

Expensive mistake, but finally have this issue resolved. Also, the OEM throwout bearings still suck. At 30k, it's throwing rust dust out of it. Had the Exedy throwout bearing I saved from the Southbend clutch put in this time.
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Old 12-05-2022, 09:59 AM   #13
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I had the clutch opened back up recently, this root cause was the Verus fork with sloppy tolerances. The shop put in an OEM fork and all is well again, no more serious bucking.

Expensive mistake, but finally have this issue resolved. Also, the OEM throwout bearings still suck. At 30k, it's throwing rust dust out of it. Had the Exedy throwout bearing I saved from the Southbend clutch put in this time.

What in the tolerance was sloppy?
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Old 12-05-2022, 12:17 PM   #14
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That is an extremely weird source for something like this...
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