'93 miata grinding noise on deceleration

After I bought this car, the noise has become more and more prevalent. it started only in 4th gear but now it has moved to all gears in different levels of volume and intensity. sometimes the car will jerk letting off the throttle when it starts making the noise, and when it doesn't make the noise, it is a nice snooth decel. I changed oils, trans oil was fine, diff oil was dark. Some have upgraded to torsens and the issue was solved, but this sound is not coming from the rear. Drive shaft or PPF may be a culprit here too. I went ahead and ripped the center console out and the outer boot so I could hear better. It sounds like it is coming from in front of the shifter. Next step is to try and replace the clutch, though it feels fine it is the one I bought it with. There is heat shield rattle but it is a distinct tin rattle and I will remove them to see if I can take that sound out of the equation. I have had no luck and this sound seems to plague many mx-5 owners. I will try to keep a well documented video series trying to fix this problem and hopefully if I fix it it will help others in this situation.

[@iansotomayor8788]

For anybody coming back. I have not fixed it. Here is what I have done, and what has helped and not helped, and what I think may be the culprit. -Clutch change-pilot bearing was toast. Replacing that was okay, but the noise did come back anyways. -fluids- trans got redline mt-90. Did nothing to help noise but shifting is smoother. Diff is shiny every time I drain it. 75w140 in instead of 75w90 helped reduce noise. -ppf- adjusting the ppf lessened noise in 4th but made it pretty even throughout all gears, constancy is good, but I still don't like it. Driveshaft is fine, diff squeaked though the winter and no longer does now that it is warm. I'm pretty sure a bearing is going bad in it and also gear lash is bad inside the diff. However, the transmission has shown some points of wear, but it may just be shifter bushings needing replacement, but Im preparing for that to be an issue too, but less likely. The car has driven fine for a happy 8k miles or so after posting this video with no real signs of any new massive wear or damage over this time. The plan is to drive this until the motor blows then either vvt swap and turbo it. Either way a torsen is going to find its way onto this car, along with the rest of the drivetrain being swapped so hopes is that a new drivetrain will eliminate the drivetrain noise. I will update again at some point when I do more to the car, college is just expensive and time consuming.

[@liamdownes]

Pretty sure I’ve got the same issue, anything worth an update?

[@Eldon105]

I got the same noise. Swapping my transmission this week with a 1.8. I’ll let you know if it helps

[@nelsoncruz712]

I just noticed this issue with my car, I’m not mechanically inclined but I have a shop I’m gonna take it to and see if they have any answers. I literally just got my clutch and flywheel replaced and now it’s making this noise. I hope it’s not insanely expensive.

[@125squad7]

@@Eldon105any news on if it fixed your issue?

[@Eldon105]

@@125squad7it’s the diff bro

[@MrTubs1212]

Hey man. Read your comments and wanted to provide some input from my experience. I have a 91 and just changed the clutch, flywheel, throwout bearing, and pilot bearing. My car made the same noise before and still makes it after. The springs on the clutch I took out looked brand new. I also made sure the ppf alignment was within spec and it still makes the sound :/

[@iansotomayor8788]

Yeah, I did the same, I think it's gotta be differential or drive shaft related. If not that I haven't a clue other than internal transmission stuff is worn which I really don't want to be the case. If anything the sound is worse now since I've driven it despite all my work gone into trying to get rid of it.

[@MrTubs1212]

@@iansotomayor8788 I planned on putting a 4.1 out of a msm in my car hoping itd magically disappear but the guy absolutely mushroomed the threads on an axle taking it out

[@silvan1995]

So clutch is in good shape. Next things would be gearbox or diff. I'm having the same issue on NA6 and I might think this noise comes from the diff. Would be great deal to swap diff and see if it sounds good.

[@iansotomayor8788]

@@silvan1995 I think it is diff related as well, or driveshaft. Just load on it I think is the issue. I want to autocross this car so I'll probably pick up an open 1.6 for cheap and throw it on with a new driveshaft until I decide if I want to do engine performance mods then up to the torsen, or try my luck with another vlsd.

[@silvan1995]

@@iansotomayor8788 yeah... also there's people that says it is gearbox issue..... mysterious

[@laelronchiatodjk]

I too had the exact same problem (nbfl 1.8vvt sport 2003), I too bought the car that made this noise. I finally found out that it was the bearing between the driveshaft and differential, that of the differential pinion. changed the diff and the noise is gone completely.

[@iansotomayor8788]

This sounds like a very likely suspect, and one I've thought of too. Money is not here right now, but when it is that will be something I definitely will look at replacing.

[@laelronchiatodjk]

@@iansotomayor8788 I understand. I had the car with the noise for months before I could try changing the diff. I had to speed things up because while I was trying to figure out where the noise was coming from, I changed the differential oil (it was very dirty and thick even when hot) but in doing it and putting in new oil, after a few days oil began to leak from the bearing of differential pinion, so I had to change the diff, as it's the Daily car, and luckily the noise is gone too. at this point I would advise you to try changing the differential oil, even with a poor quality one, just to try if the noise fades, or if it starts to leak oil like me. Of course if it starts leaking oil like it did to me, you will find out what the problem is but at the same time you are going to have to change the diff if you want to continue using the car, so do it when you can afford it. Then maybe that's not the problem in your case, but an oil change is cheap and can help you find the problem.

[@paullomecio4428]

Hey I know that this is an old comment but do you remember what the part # for the bearing?

[@TheWoundedNinja]

Apparently the 90-93 miatas with the 1.6L engine had like a bad fitting diff or whatever and would make this noise. People are claiming it has no effect on the performance of the car but rather it just sounds super annoying. To fix, people would usually change over to the 94-97 miata Differentials which had a better build on the Diff.

[@zwonk741]

i have a 97 miata and it still makes that sound

[@chickenpotpieboy1]

Same exact noise on my 07 rx8. Any luck?

[@ucnguyen3956]

It's the transmission. It went mostly away when I changed to a torsen rear end. Basically with a lighter flywheel and small rear end there wasn't enough dampening in the dynamic system, the crunching is the gears vibrating off each other when Unloaded this is the most reasonable up to now with me as I've searching everywhere !

[@ucnguyen3956]

"caused by the gears rocking back and forth into each other as a result of no real dampening in the driveshaft and differential of the 1.6l mx5"

[@lemuelpadilla1776]

I'm having the same issue. any luck? When you went through changing your clutch, did you happen to inspect the throw out bearing? Just wondering if you saw anything?

[@iansotomayor8788]

Throw our bearing was fine, my pilot bearing was in really bad shape, but I never actually fixed the issue unfortunately. Maybe it's diff related or it's just clutch springs hitting the flywheel. I haven't figured out yet.

[@Nxri.-]

Do u know what made that sound?

[@VViralVibes]

Did you find out if it was your diff?

[@2seater_mx5]

hi i know its an old-ish video but i just got myself a 99' NB and has a noise pretty similar than yours in the video. when i clutch it's okay, was yours the same? the noise only happens when deceleration in gear (like engine braking)

[@iansotomayor8788]

The only things I've done that have made a difference was the ppf alignment(slightly lessened noise in 4th, but made it louder in 3rd) and diff oil(75w90 to 75w140 which made it quieter). I'm assuming it is the diffs fault because the oil is silver every time I change it. I'm going to be switching to a torsen diff sometime this year so I'll see if that works, and if not it's probably my transmission that has 215k miles now. I did change my clutch at one point and the polit bearing was toast so maybe it's happened again because it was less after that change, but did come back. For an nb, I would start with ppf adjustment and swapping fluids. Avoid taking anything out if possible, I'm just at the point where it's time to cut my losses and make an upgrade. My plans are to vvt swap and turbo this car so everything is going to change eventually anyways. Just waiting until the 1.6 blows up tbh. If it's any consolation, I've driven with this noise for 15k miles and the drivability has not changed.

[@JElNZ]

I have the exact same issue. It all started after I installed new clutch, lightweight flywheel and 6speed gearbox. It’s so annoying!! I have spent a whole day modifying the height of the gearbox-ppf and testing to no avail. Do you have a lightweight flywheel? I am starting to think that’s the issue. either that or my 6speed is fried.

[@iansotomayor8788]

I don't have a lightweight, though I have heard that they do tend to make this noise. If the 6speed was fine pre-flywheel I think it's fair to say the flywheel is the issue

[@larrybailey5080]

This is just a diff whine. Nothing to worry about

[@iansotomayor8788]

Diff whine and gear lash are very different things. I'm not worried about the whine.

[@baronrichmond5667]

My 2016 started rattling like this since about 50,000 miles (now at 100k) and it's so loud that it makes me want to sell the car. Dealer couldn't find a fix but gave me a new transmission on the house and that didn't fix it. They aligned PPF as well and still terrible rattle. Changed trans fluid, no luck. Seems like I'm doomed.

[@xxxxSHADOWxxxxxX]

Hey mate same thing in my na. You had any luck yet?

[@iansotomayor8788]

Well, I went through and changed my clutch and bearings out. Pilot bearing was completely fried. Changing that out stopped my jerking on decel and the noise is MUCH softer but still present. I'm thinking the noise may be linked to clutch springs because on the old clutch the springs were pretty marred. I'll adjust the ppf next time I have some time off, a lot of forums have said to adjust it higher and it helps. When I do I'll post another video similar to this one. I'll explain my thoughts and processes I went through there too.

[@bladerunner_559]

@@iansotomayor8788 any luck?

[@iansotomayor8788]

@@bladerunner_559 not really, but I'm about 80% sure it's the diff

[@tomtaylor5950]

Might sound silly, but I had this noise and could solve it, realized my car was dangerously low on engine oil, topped it up and the sound went away

[@joshirwin7904]

had this sound and got gearbox rebuilt and clutch/flywheel. in a evo 5. still making the noise esp in 4th gear decel at around 2.5krpm. sounds like its coming from the rear. Very odd. Other videos said its possibly from lightweight flywheel. dont know exactly.. annoying

[@iansotomayor8788]

Yeah, I've heard lightweight flywheel too, but I don't have. I'm gonna throw a 150 buck open diff on the thing and see if it fixes the issues I'm having while I don't have money for a torsen

[@Sertao2013]

You need to align your transmission and your ppf . Watch the videos on how to to do a ppf alignment .

[@charliebennett7850]

I have the same problem in my MSM. It never made noise until after I got the clutch done.

[@iansotomayor8788]

I've heard some things about the clutch springs rattling, so I don't think the clutch is out of the question. I haven't been able to fix it, but it isn't seeming to cause issues either, just annoying

[@charliebennett7850]

@@iansotomayor8788 I adjusted the PPF today and it pretty much fixed it. Still some very muffled grinding noises but it’s 99% gone!

[@iansotomayor8788]

@@charliebennett7850 I adjusted the ppf as one of the first things I did and it moved the grinding from 4th gear mainly to 3rd mainly. Maybe my driveshaft is wearing out tbh, but it hasn't gotten better or worse so I'm okay for now. No fix yet for me and my na

[@jmooch59]

Was it an OEM equivalent or stage 1+ clutch? I had similar issues after my clutch was replaced. My mechanic replaced it with a stage 1 clutch (for what reason I do not know he said it was $10 more or something). The stiffer springs seem to be a thing.

[@rachelpurity1]

@@jmooch59 So stiffer springs on an upgraded clutch make this noise?

[@chill.spooky594]

It’s you’re diff fluid go change it

[@iansotomayor8788]

I promise you it isn't, I have completely drained it and filled it 3 times.

[@chill.spooky594]

@@iansotomayor8788 Fuxk because I got the same shit happening to me I didn’t change the fluid yet and was going to see if it would fix it but you already did it yours sounds worse than mine

[@chill.spooky594]

@@iansotomayor8788 might be the front diff my sound like that is coming from the front of the car but my shit drives fine I just don’t know what the sound is either so let me know if you found what it was

[@chill.spooky594]

@@iansotomayor8788 also might be a bad wheel bearing have you changed that

[@chill.spooky594]

@@iansotomayor8788 mine is when you let off the gas