transmission ?? noise in NA 6, looking for suggestions

[michael]

Hi all,

I have an NA6 that has done 80,000k's and it has a daiken clutch in it that has done about 10,000 k's. The car has never been dríven hard. When decelerating with throttle off and using engine resistance, the car makes a noise that sounds a bit like a metal threaded gear knob vibrating when loose on the gear stick. The noise sounds like it is coming from the drive train, but I can't tell whether it is gearbox or diff or something else. I have checked all the heat shields and exhaust brackets and they all seem tight.

Has anyone had this problem and can suggest possible causes / solutions.

I have also taken it to an MX5 mechanic \"MX5 Plus\". They had no real suggestions. Can anyone suggest an MX5 expert in the Brisbane area that perhaps I could take the car to.

Thanks for your help.
Michael

[StanTheMan]

kind of a rattle? does it come & go with certain RPM's?

First thing I'd check is some of the heat shields on the excaust.
possebly even the excaust itself. The earlie NA's were famous for heat shield rattles.

[JBT]

I'd still be investigating sources of noises from loose heat shields, baffles or exhaust system rattles/rubbing.

Can anyone suggest an MX5 expert in the Brisbane area that perhaps I could take the car to.

There is this guy John Kraschnefski. I hear all good things about him and will go to him if I ever have a future problem with mine. He is out Ipswich way - 3812 0616.

Sounds like the throwout bearing if it's just on deceleration.

Why? The TB is doing nothing in particular except when the clutch pedal is depressed.

Since you have a heavy duty clutch you're probably prone to premature diff failure?

Why? The clutch has nothing to do with the diff.

[OMY005]

What suburb are you in (home or work)? Maybe one of us could have a listen for you?

Andrew.

[ZenArcher]

I have been doing lots of research on this as well.

Reading through the big forum (miata.net) they have stacks of information on their under topics like \"grinding noise under deceleration\" it is noticeable after a clutch change.

The common denominator with all the comments was that the noise disappeared after the diff had been changed/upgraded. A lot of the guys there had played around with lots of things such as bearing changes PPF height/angle etc I played with the angle and height of the PPF and this had a small affect. I had the noise occur after Mania installed my new clutch but they felt that it was caused by the clutch needing to be bedded into the original flywheel. The noise has gotten quieter, but not disappeared.

But recently one of the forum users (on miata.net) worked it out that it looked to be that the replacement diffs that were being installed had a vibration damper on them - with most diffs being upgraded to the 1.8 diff. I had a look at this when I was at Carco the other day, while Dave and Russell were working on my MX. They had an NB on the hoist and I had a look. There is what looks to be a vibration damper on the rear diff. Though unfortunately this can't be retrofitted to the early diffs unless the diff is taken apart as the dampener is a one piece unit. Apprently this dampener is fitted to all NB's onwards, but I am not sure about the NA8's, but it wasn't fitted to the NA6's.

I also noticed though, that the noise is louder if you have a short shifter. As when I installed my short shifter the noise got very loud in all gears, whereas it was really only audible on deceleration in 2nd gear and only on odd occasions and much more quieter in 3rd.

Just my 2 cents worth - but I am no expert on the subject, I've just done lots of reading about the problem.

[rodent]

Since you have a heavy duty clutch you're probably prone to premature diff failure?

Why? The clutch has nothing to do with the diff.

Wouldn't the diff cop more of a beating if the clutch bites harder?

[StanTheMan]

Since you have a heavy duty clutch you're probably prone to premature diff failure?

Why? The clutch has nothing to do with the diff.

Wouldn't the diff cop more of a beating if the clutch bites harder?

its not the clutch which is the problem Its the user. The heavie duty Dainkin Cluch is not all that much heavier than OEM. However with heavier cluch You ususually get heavier clutch dumping by the driver.......so eventually.....as the diff is the weakest link along the 1.6 driveline....same result.
One of those ceramic Button Cluches.....yes I'd be very concerned about almost instant diff failure.....not so much with the Dainking clutch.
but in the end it all comes down to how its dríven.

My 1.6 diff lasted 200k km.

[93_Clubman]

Has anyone had this problem and can suggest possible causes / solutions.Michael

fwiw, if you do a search of daiken/ daikin on here &/ or the archived site you find at least a couple of threads which mention a noise when daikin clutches are fitted.

[jules]

Just a little off topic there are a couple of other possibilities.

1/ The Daiken clutch plate springs are rattling and
2/ The little known and \"grey\" issue of the shifter rods rattling in the housing which affected Malibu, basically caused by gearbox housing wear. You may have read about this on the big forum, which I trolled for days a few years back trying to find the source of the noise. A technician imported from Mazda Japan finally tracked down the problem and fixed it for good.


Jules

[Juffa]

I have had this same noise on all three of my MX-5s, and it happened after the clutch was changed. I know that the first MX-5 had a Mazda Clutch installed, not sure about the other two as the previous owners had done it in preparation to sell the cars.

After installing a Torsen diff out of a 2001 NB the noise has gone. I replaced the diff, not to get rid of the sound, but to remove a potential point of failure after my turbo install.

J

[michael]

Guys,

Thanks for the info, I couldn't respond last night as I had internet troubles. The noise has only started in the last 1,000 ks (only on engine braking, any gear, any revs). The clutch is about 10,000ks old. The car is dríven VERY SPARINGLY so I don't think that hard driving has contributed to the problem.

Any other thoughts would still be much appreciated.
Thanks
Michael

[JBT]

You say the car has never been dríven hard but you also say that it has had a clutch replacement at 70,000km. Was that due to wear abuse by a previous owner or because of another problem with the clutch? If it was the former then it could be a case of gearbox (bearings, bushes, linkages) wear.

[michael]

The previous owner was a woman who had it for most of the time since new and I think used to ride the clutch in traffic.

[desertfox]

I had the clutch replaced with a heavy duty clutch and it made a rattling sound afterwards between 1500 to 2500rpm. My regular mechanic pulled the gearbox out again but could not figure it out. Brought it to a specialist and they believe that the springs on the clutch plate might be loose. Apparently, MX5's are sensitive to it.

[jules]

any gear, any revs

That's the clue guys.
Most MX-5's will only complain and rattle around the dreaded 3,500rpm. If it's doing it in any gear, in any revs, then I'd say it could be something VERY worn or very loose/outside of tolerance.

Jules