Light flywheel chatter
 

So I know a light flywheel creates clutch/gear chatter, but I'm not entirely to sure what I'm hearing is 'chatter'. What I'm referring to is the 'knocking' sound at around the 2nd second, and 11 seconds and on.

ACT CLUTCH XTSS (315fl lbs.) - Street Full Faced
ACT Flywheel 13lbs

Now my transmission is brand new, it was built by jomotors, and it shifts totally fine. Feels great too, just a little worried about the noise. I tried multiple times to align the PPF, but it doesn't really change the sound. Maybe I'm aligning it wrong?


When I push the clutch in, the chatter kind of fades away, but if I rev it I can still hear it. However when under load noise is pretty much gone, and sounds fine.

I don't hate the sound, just wanna know if its actually gear/clutch chatter.

Doesn't sound like flywheel chatter to me, but also doesn't sound terribly dangerous either. So full power through all the gears no issue? Just this low speed chatter?

You replaced your throwout bearing and adjusted your clutch pedal right?

Is your PPF angle correct?

yup all new. And I believe I adjusted properly. Car is unturned so I haven't really given her full beans. But it doesn't slip on 11lbs of a quick spool.

I tried to allign it acouple times, but sound doesn't go away..
Probably I'm not doing it right. I slightly jack up the trans when I tighten up the PPF.

Can't give it full power yet as I'm unturned at 11 lbs of boost, but when I'm accelerating. Sounds smooth.

Clutch "chatter" commonly occurs during clutch engagement.
40 years experience, I've never had clutch chatter occur when clutch is fully engaged or fully disengaged.
That sort of sounds like a countershaft bearing or maybe a PPF mis-alignment.
Next thing I would do is place car on lift and try to recreate noise.

If I could with the suspension and rear tires unloaded I'd use a mechanics stethoscope to isolate the noise in the transmission.
End of bellhousing (beginning of transmission), center plate, rear housing would be my initial check points.

A bit of knowledge, the countershaft is loaded in all of the gears EXCEPT the gear that is 1-1. on MOST 5 speeds this gear will be fourth but you should verify.
In the 1-1 gear the transmission has locked the input shaft into the output shaft and the tranny is basically a straight shaft, no gears at all are in use and the counter shaft is completely un-loaded.
If you can hear noise in every gear except this one the problem is inside the transmission.

If I couldn't recreate the noise with suspension unloaded I'd look to PPF alignment. Try it at both ends of it's travel. Does either position vary the noise?
Or maybe the output bushing is worn/too much clearance. Is the drive shaft yoke loose in the tail housing?
Or maybe a bad driveshaft u-joint/bad driveshaft, bad 1/2 shaft, etc...

Another check would be "can I feel the noise in the clutch pedal?" Bad TOB, bad pressure plate, mis-aligned TO fork, CLUTCH CHATTER (I've always been able to feel clutch chatter in the pedal).
I don't think this is the case with the short video you posted.
Feel the noise in the shift level-transmission, shifter turret...
Feel the noise in the "seat"- drive line.

Lots of threads mention PPF alignment. Just lifting it slightly is not correct. There is a measurement from bottom of frame rails to bottom of PPF bracket at mount on transmission. As I remember it's something like 60mm.
If I was aligning one I'd look through those old posts to verify this measurement as even I don't fully trust my memory...

Is the disc solid or is it "sprung". A solid disc can transmit/create noises. It may be just that.
I don't like solids for street use, too much noise...

I think what he meant is, the transmission raises a little as the PPF bolts are tightened.
This happened to me, too. Starting from a lower point or forcing the trans down while tightening the bolts helps.

Just for kicks:
Could lug nuts be loose?

Also throwing it out there, but check unrelated things. My GT500 I swore with it's new clutch had some horrible chatter. Turned out one of my cat's had broken in exhaust and was rattling in muffler and I could hear it by the head. I wish you luck in your search.

Throwing out some other ideas. My 3" downpipe sometimes comes in contact with my subframe and makes the exact same noise. I feel it in my feet near the trans side of the footwell.

Edit: It usually happened to me when in cruise/light load, or in decel. It varied depending on how the downpipe was feeling. Never under load though.

Custom downpipe?

Oh no, not sure why I made it sound like my own. It's the Kraken 3in with the cast elbow. My old custom 3in exhuast would physically apply a torque on the downpipe and twist it in the vband clamp which eventually led it to contacting the subframe. I think my stock motor mounts are a little worn out too and make it rock around quite a bit.

Just went through some old videos. The rattle in the video is a little different from your vid, but your vid sounded just like mine when it wasn't so extreme.

I actually just took the car out and did a couple of donuts and pretty much abused it a bit. And the sound went away lol. Not a single knock anymore. soooooooooo, idk what was causing it. Maybe just break in noise? Although sounded pretty extreme for break in noise.

However I'll be jacking the car up later and making sure everything is tight.

Well good thing I checked, the one bolt at the end of the trans was just chilling, ready too unscrew itself off the car lol.

I guess it was misaligned and the power moved it in the right alignment. But unscrewing a bolt in the process.


Edit:
Turns out my impact gun isn't very good tightening bolts. All my PPF bolts needed extra torqueing with a wrench.

Aligned it and torqued it down. Car feels waaay better now. Also no knocking!

DO DONUTS AND ALL THINGS WILL FIX THEMSELVES!!!!

Let this be a lesson to us all, donuts. That is all for now.

Glad it's fixed. I'll try donuts next time I hear some rattles.

Don't forget to double check your bolts afterwards 😅

GLAZE ALL THE DONUTS!
and check your ppf angle

Turns out the Godless one was correct!
He is sort of a bad ass. I loved his car under all those lights!
It wasn't loose lug nuts but it was a loose fastener...

After 40 years of wrenching I use almost NO air tools anymore.
For tear downs maybe
Never for installations