Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - View Single Post

vfrqqq · 06-29-2021, 04:08 PM

So I recently replaced my stock clutch with an SBC Stage 2 Daily clutch since I was going in to replace the failed clutch release fork. In doing so, I had the flywheel resurfaced versus replacing it with a new flywheel. After I completed the installation and tested everything out, I discovered that I have a new slight sort of shuddering vibration from the engine/transmission that starts right around 2,800 rpm and goes away at about 3,200 rpm. Based on what people have described, it does not seem like this is due to clutch chatter, particularly since it occurs regardless of whether the transmission and engine are engaged and is repeatable. I would also note that, before the new clutch, there was no such vibration at any engine speed.

As such, this really makes me think that there is a rotational mass imbalance somewhere that I didn't account for. The problem is that I'm not sure what else I could have done to prevent this from happening during the install, save for not realizing I needed a special piece of equipment to balance the flywheel, clutch, and clutch cover before installing it on the car. I marked the flywheel at the 6 o'clock position before removing it and then installed it in exactly the same orientation. I have a hard time believing the clutch and/or clutch cover have any significant imbalance as there are only three orientations you could choose from as the flywheel posts are separated by 120 degrees, but an imbalance could be at any point in between those orientations. As such, I'm wondering if that implies the flywheel and clutch have to be balanced together, presumably on some specialized equipment. If so, it would seem I have one of two options:

1. Install a new flywheel with my new clutch (i.e., ~100 break-in miles on the clutch) and hope it is balanced; or

2. take the existing or new flywheel, clutch, and clutch cover to get balanced at a shop, if that is in fact a thing.

I'm of course loathed to take my transmission down again, especially without having a sure success path, but I also recognize ignoring the problem could lead to bigger issues down the road as a small imbalance in the rotational mass can have big consequences at high engine speeds, or even just around those engine speeds where the vibration is most prominent.

06-29-2021, 04:08 PM	#184
vfrqqq Ultra Senior Member Join Date: Feb 2014 Drives: 2014 BRZ Premium, WRB Location: East Coast, US Posts: 209 Thanks: 43 Thanked 60 Times in 37 Posts Mentioned: 6 Post(s) Tagged: 0 Thread(s)	Replaced Clutch and Now Have Apparent Rotational Mass Imbalance So I recently replaced my stock clutch with an SBC Stage 2 Daily clutch since I was going in to replace the failed clutch release fork. In doing so, I had the flywheel resurfaced versus replacing it with a new flywheel. After I completed the installation and tested everything out, I discovered that I have a new slight sort of shuddering vibration from the engine/transmission that starts right around 2,800 rpm and goes away at about 3,200 rpm. Based on what people have described, it does not seem like this is due to clutch chatter, particularly since it occurs regardless of whether the transmission and engine are engaged and is repeatable. I would also note that, before the new clutch, there was no such vibration at any engine speed. As such, this really makes me think that there is a rotational mass imbalance somewhere that I didn't account for. The problem is that I'm not sure what else I could have done to prevent this from happening during the install, save for not realizing I needed a special piece of equipment to balance the flywheel, clutch, and clutch cover before installing it on the car. I marked the flywheel at the 6 o'clock position before removing it and then installed it in exactly the same orientation. I have a hard time believing the clutch and/or clutch cover have any significant imbalance as there are only three orientations you could choose from as the flywheel posts are separated by 120 degrees, but an imbalance could be at any point in between those orientations. As such, I'm wondering if that implies the flywheel and clutch have to be balanced together, presumably on some specialized equipment. If so, it would seem I have one of two options: 1. Install a new flywheel with my new clutch (i.e., ~100 break-in miles on the clutch) and hope it is balanced; or 2. take the existing or new flywheel, clutch, and clutch cover to get balanced at a shop, if that is in fact a thing. I'm of course loathed to take my transmission down again, especially without having a sure success path, but I also recognize ignoring the problem could lead to bigger issues down the road as a small imbalance in the rotational mass can have big consequences at high engine speeds, or even just around those engine speeds where the vibration is most prominent.