Drivetrain clunk
 

Hi all, long time no post.

I’ve recently noticed a clunk and a noise in the rear of my car. It seems to happen on cold starts, when I first roll out of my garage and right when i fully let the clutch out in first, literally within 10-20 feet. After this I can’t seem to be able to replicate it on the ground. I put the car up and tightened all of my PPF bolts and diff fasteners with no change. Posted to Trackable Miatas on FB with a few different suggestions, the worst of which being a broken tooth in the diff. I had a driveshaft go on me last year that I found under different circumstances and it was a very different sound, although I’m suspicious this one may be a u-joint issue as well. There is no obvious play in it, but again last year it was the same story - sound went away when I replaced my driveshaft. I hope my video has attached correctly. I have the car in the air and letting the clutch out in first. Thanks guys.

Further edit: there is only ONE clunk when it is on the ground. The rattle is different when in the air. I figured they were relevant.
Here is a YT link to the video:

My NB1 has a bit of driveline clunk when letting the clutch out in first from a dead stop. I decided to just live with it and nothing ever came of it. I figured it was just driveline slack.

I have the same damn thing. Cant figure it out but if I keep the rpm higher it doesnt happen

I also have this issue. Living with it as I haven't found a cure, think its just normal drivetrain noise.

While I don't know the answer, I wonder if reclocking the drive shaft 90 degrees would yield any positive or negative effects.

I'm going to go out on a limb and guess it's the pinion spacer (if OEM). I'm speculating that after several hard turbo launches and decel during autocross or track, the spacermight not be able to keep the bearing preload

I made this up, no clue. Symptom would probably be a screaming diff, not a clunk.


https://i.ebayimg.com/images/g/pfsAA...8GA/s-l640.jpg

Thanks all, I’m glad I’m not the only one. I think I’m just gonna live with it. I tracked the car last weekend and it was perfectly fine. Full send.

I wonder if adding a PPF brace would change the noise, or maybe stop it entirely? Also could cause something important to break instead of a noise being made

Pretty sure this will end up having something to do with that clunk.

https://cimg1.ibsrv.net/gimg/www.mia...f79a11ff2b.jpg

Selling these if interest
https://cimg9.ibsrv.net/gimg/www.mia...b58bbcf697.jpg

My car does this exact same things for the last 2 years , never found the problem.. still drive good with it ..

Gonna revive a dead thread and say to check if your flywheel is loose. My car made a nearly identical sound, and had what I thought was a rear main leak. When I pulled the transmission to replace the rear main, I found the flywheel had a loose bolt. Turns out my rear main wasn't leaking, as the oil was coming from behind the loose bolt. FYI the crank shaft leaks if you don't use thread sealant with loctite on the flywheel bolts.

Oh shit, I just I installed a new clutch/flywheel... I'll check my bolts when I install the new diff.

Did the sound go away when you tightened the bold? Also, was it making any other noises? Just to note: loose flywheel bolts are a SERIOUS and DANGEROUS problem.

Now I am literally in the same situation you are. Just swapped my clutch for a Supermiata Sport Organic Sprung clutch. I am also getting ready to swap in another diff. I will say that I had the sound before the clutch install. Why are you pulling your trans when you install your new diff?

When I put my car back together, the sound stopped, and was only making a noise similar to the video, but it did get a bit louder as I limped the car home. I was extremely lucky I didn't get a saw blade of a flywheel through the floorboard.

I'm having a drive line issue when I launch. Horrible shaking/lurching. (Been lurking on this thread for ideas) One of the Old Farts™ at the shop I use said it sounded like oil on the clutch. I don't think that's it... BUT I always listen to Old Farts™ and I'll have the diff out (1.6 -> 1.8 diff swap) anyways. I torqued the bolts to spec but did not use lock tight on them. For just a few bolts I figure it's worth pulling the trans to check. /2¢

I didn't notice any oil on my clutch assembly, just the backside of the flywheel, however as soon as my car made a new noise, I limped it home and didn't drive it again until it was fixed.

Im just trying to clarify sot here isn't confusion. The noise was continuous as you were driving? and then only made the noise consistent with the video after you tightened the bolts?

From what I understand, lubricant on the friction surfaces can do this. What clutch are you using? Definitely go back and put thread locker on those bolts Permatex #24300 or Loctite 243. As I think someone else stated, besides adding breakaway torque strength, it also acts as a sealant for oil.

I'm definitely going to go back and remount the flywheel. I have a FM clutch and a FX (I think) 1.8 flywheel. I can bang gears and clutch kick like normal, it's only from a dead stop where I have the issues. And it was fine on the 1.6 clutch...

It will be a while before I get to use the lift again but I'll post back then.

My noise was like the video and was only when I was using the clutch, or taking off from a stop. After I had tightened the bolts, it went away.