DIY Clutch Replacement

[zberz]

Replaced my clutch over holiday season 2019. Not very hard if you're mechanically-inclined. I'm not a pro mechanic, but I dabble. If you have specific questions, ask and I'll do my best to help.
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[vfrqqq]

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.

[vfrqqq]

So it would seem that my vibration issue is more related to the clutch disk being out of alignment since it was installed with the inadequate plastic alignment tool that comes with the kit. I don't remember how much play there was when I first installed the SBC clutch, but from a handful of videos, it would seem there is substantial play that can easily lead to misalignment. I don't fully understand how that works since I would expect a misaligned clutch disk to essentially realign itself on the input shaft after the first time the pressure plate is disengaged, but maybe someone can educate me on how that works.

I'm trying to find a billet or forged metal clutch alignment tool that is not a universal alignment tool, but not having much luck. It's a bit surprising since this would seem to be quite a common problem, unless people just deal with it and don't worry about it.

So does anyone know where to buy a billet or forged metal clutch alignment tool for the BRZ/FR-S?

[pope]

Originally Posted by vfrqqq

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.

Originally Posted by vfrqqq

So it would seem that my vibration issue is more related to the clutch disk being out of alignment since it was installed with the inadequate plastic alignment tool that comes with the kit. I don't remember how much play there was when I first installed the SBC clutch, but from a handful of videos, it would seem there is substantial play that can easily lead to misalignment. I don't fully understand how that works since I would expect a misaligned clutch disk to essentially realign itself on the input shaft after the first time the pressure plate is disengaged, but maybe someone can educate me on how that works.

I'm trying to find a billet or forged metal clutch alignment tool that is not a universal alignment tool, but not having much luck. It's a bit surprising since this would seem to be quite a common problem, unless people just deal with it and don't worry about it.

So does anyone know where to buy a billet or forged metal clutch alignment tool for the BRZ/FR-S?

Clutch alignment tool positions the disc so the input shaft will go in and everything will slide into place so the transmission can be mated to the engine. If the transmission is bolted to the engine, the disc alignment was fine.

I'd say, either the clutch disc and/or pressure plate were improperly balanced from the manufacturer or your flywheel was not properly balanced by whoever surfaced it.

[vfrqqq]

Actually, the machine shop didn't rebalance it after I had it resurfaced, probably since I didn't think to ask. If they only removed 0.030 in of material from the contact surface, would it really be that easy to unintentionally remove more or less in one spot than another? I'm struggling to understand how they could have messed it up so much that I wouldn't have probably seen the error when they were finished, and it looked very uniform when they gave it to me. But I could be wrong.

As far as the pressure plate being out from the manufacturing process, I understand it's not impossible for it to have been missed, but I also tend to have a hard time seeing how a manufacturer would allow parts that need to be precision balance go out the door without having met their specifications. That would seem to give them a garbage reputation for reliability.

Regarding the clutch disk alignment tool, I was able to get my transmission back on the engine eventually, but not before I had made some unsuccessful forceful attempts. So if the clutch plate was out of alignment, but I was able to ultimately install the transmission, it sounds like you are saying the transmission essentially got the clutch disk back into position on the input shaft splines, no?

I'm concerned about rebalancing the flywheel and pressure plate as I was under the impression the flywheel is balanced together with the crank shaft during the assembly process. As such, wouldn't balancing the flywheel/pressure plate, but not together with the crank shaft potentially put them out of balance?

[pope]

Originally Posted by vfrqqq

Actually, the machine shop didn't rebalance it after I had it resurfaced, probably since I didn't think to ask. If they only removed 0.030 in of material from the contact surface, would it really be that easy to unintentionally remove more or less in one spot than another? I'm struggling to understand how they could have messed it up so much that I wouldn't have probably seen the error when they were finished, and it looked very uniform when they gave it to me. But I could be wrong.

Ideally, removing an even layer of material would not change the balance. But was the layer removed an even layer? .030” from the highest point might have only been .025” from another point. The whole reason for surfacing is to make a non-uniform surface uniform. Did the material removed have enough variance to create an imbalance

Originally Posted by vfrqqq

As far as the pressure plate being out from the manufacturing process, I understand it's not impossible for it to have been missed, but I also tend to have a hard time seeing how a manufacturer would allow parts that need to be precision balance go out the door without having met their specifications. That would seem to give them a garbage reputation for reliability.

Shit happens all the time in manufacturing. It’s it likely the new clutch and plate were imbalanced, probably not. Is it possible, yes.

Originally Posted by vfrqqq

Regarding the clutch disk alignment tool, I was able to get my transmission back on the engine eventually, but not before I had made some unsuccessful forceful attempts. So if the clutch plate was out of alignment, but I was able to ultimately install the transmission, it sounds like you are saying the transmission essentially got the clutch disk back into position on the input shaft splines, no?

If the disc is on the spines and the transmission is bolted to the engine, it’s aligned. However, depending on what happened during your “forceful attempts” you may have bent or otherwise damaged the clutch disc, pressure plate fingers, throw out bearing, input shaft, etc…

Originally Posted by vfrqqq

I'm concerned about rebalancing the flywheel and pressure plate as I was under the impression the flywheel is balanced together with the crank shaft during the assembly process. As such, wouldn't balancing the flywheel/pressure plate, but not together with the crank shaft potentially put them out of balance?

No. I mean technically yes it’s possible, but as long as the individual parts are balanced within spec, they will remain balanced when assembled. Subaru isn’t perfectly machining individual flywheels for each engine. If that was a necessity, aftermarket flywheels would be nonexistent.
In general, pistons, rods, and crank will be matched to each other to a target spec (although in a boxer configuration matching crank throws to rods/pistons isn’t even a necessity an long as the crank is balanced to itself). Flywheels (etc) will be balanced to the target spec (0oz, 28oz, 50oz, etc. imbalance (can anyone tell i grew up around fords)). Then, if the manufacturer is building engines to a (let’s say) 50oz spec, any 50oz flywheel for that engine model is going to be fine. 0oz (aka neutral balance) engines will use 0oz flywheels, 28oz will use 28oz, etc…

If you’re certain the vibration originated with the clutch replacement, start by dropping the trans and looking for damage. If nothing is obvious, have the flywheel balanced. Then, reinstall and see if the vibration is gone.

Actually, first, unbolt the driveshaft, rotate it 180* relative to the rear-end, re-bolt and torque to spec. I have no idea why this sometimes works, but sometimes this works.

[vfrqqq]

Thanks for the feedback. At a minimum, I'll be removing the trans today to inspect for visible damage. Beyond that, since I bit off a little more than I could chew, I'm thinking I may just take it to a shop and have all new parts installed by certified mechanics and hope I can salvage something from first install. Regarding the case where there's no visible damage to the clutch plate or pressure plate, you wouldn't say the pressure plate also needs to be balanced as well as the flywheel?

[pope]

it wouldn’t hurt, but probably not essential.

[ermax]

I’ve never heard of someone surfacing a FW without also making sure it’s balanced but if I had to guess, this is where your problem is if it’s not the driveshaft. Did you mark the drive shaft before removing it?

[vfrqqq]

Yes, I marked the drive shaft and reinstalled it in the same orientation. Same with the resurfaced flywheel.

[vfrqqq]

Ok, so I removed the transmission and I can't see any visible signs of damage. When inspecting the clutch disk, I used a straight edge to check both side in four orientations 90 degrees apart by simply placing it flush across the clutch disk material. I also measured the thickness in about 8 to 10 different spots around the clutch disk and all measurements came up to 0.32 in with a variance of about plus/minus 0.002.

Something did catch my eye on the pressure plate as shown below in the picture. The pressure plate surface look uniform except for one spot that maybe showed some slight discoloration. I'm kicking myself because I have zero pics of the pressure plate surface before the install and ~100 miles I already put on the clutch, so I don't know if it was pre-existing. Perhaps it came about as a result of the vibrations I was experiencing, but I guess I'll never know. Anyway, otherwise the pressure plate and clutch cover looked to be in original condition.







As far as the flywheel is concerned, I could see no discoloration in the surface material and otherwise no visible signs that there was a hotspot. Below is a pic of it on the engine.



So anyway, I'm quite torn.

On the one hand, it seems a safe bet to just remove the flywheel and have it balanced at a machine shop, which will cost me $100 bucks.

On the other hand, I'm wondering if I should just bit the bullet and get a new flywheel (I can pick up an Exedy OEM flywheel from Subispeed.com for about $140), which presumably will be neutrally balanced, and so that both the flywheel and clutch are new. But that assumes the engine is also neutrally balanced. I tend to lean toward this option, especially since I'm already $75 in for the resurfacing of the OEM flywheel.

I'm also just wondering if I should just reinstall the clutch and transmission and see how it goes now that I have a forged metal clutch alignment tool. The metal alignment tool is certainly more precise than the goofy plastic one that comes with the clutch; however I didn't see that much difference in the play of the clutch disk between the two when installed on the flywheel, but perhaps that small difference is really all it takes.

Anyway, happy 4th of July. I hope people are having more fun than I am

[ermax]

As already stated, the alignment tool is only used to get everything to align just enough to get the shaft through. As soon as you press and release the clutch it all moves freely. It isn’t like you align the clutch with the tool and it’s locked in that spot forever. It’s solely for installation. This isn’t the source of your vibrations. A machined alignment tool is totally worth having though. It’s annoying when you align with a sloppy plastic one and then can’t get the shaft through and then have to loosen all those damn PP bolts all over again.

[Feezz]

Great!!
Perfectly and detailed described, Thanks

[blsfrs]

IMO. It's not the flywheel or the "alignment". I'd replace the pressure pate and disc. It's new. see if your supplier will give you an exchange.