whining noise on down run, coming from centre of car?

[revhead]

hey guys and gals, been driving my mx5 a lot lately and recently I have noticed that after about 30 mins of driving when everything has warmed up properly, (engine, transmission, diff, etc..) when I am in 3rd or 4th gear and I have my foot off the accelerator (cruising to lower speed a little) I get this slight whining/whirring noise from down near the centre console/ shift leaver area. it’s not the shifter so I’m assuming its somewhere in the transmission?
What is this noise? Is it hurting anything in the car? Why is it happening? How can I stop it from happening?

I have changed the engine oil and gearbox oil to semi syn thinking it would help keep temperatures down and stop the noise but didn’t help. I did some googling and didn’t get much, some people mentioned something about a throw out bearing, thrust bearing?

Any help would be great, I really don’t want to be inadvertently doing damage to my car!
Also, I noticed this soon after my brother wanted to have a drive.. He stalled the thing about 7 times just going around the block.. Could this be a contributor to any damage caused?

[NitroDann]

Its almost definately a bearing.

Id guess diff if its an na6 because they are notorious for failing due to the bearing which control the input shaft on over run or in reverse.

Basically there isnt much you can do except wait for it to become bad enough it either fails or becomes obvious which part, if its in the gearbox area change the box and clutch while you are down there along with the clutch bearings, if its the diff get a new diff.

Dann

[93_Clubman]

If you're talking about a 5 speed GB in an NA6, then when you did the oil change did you also clean out & replace the small amount of oil in the GB turret to which the gear lever is mounted?

[manga_blue]

You might also have 20 year old oil in the diff. If that's the case then changing the diff oil to something fresh might hold off diff bearing failure for a year or two longer.

[aka_juffa]

Ok, my turn.

I am going out a limb here and suggest that what you are hearing is lash in the drive train. All 3 of my previous NA6 MX-5s suffered from this, usually after the clutch was replaced. A search of the big forum found the following thread.

http://forum.miata.net/vb/showthread.php?t=320965

It appears that the sound is caused when the gearbox and PPF are reinstalled out of alignment after any work, such as a clutch change, where the gearbox is removed.

J.

[NitroDann]

Caused by the university joints non linear twisting being out of synch? I've never ever considered that..... Could explain. Some things I enjoy wondered about for years.

Thanks for the insight!

Dann

[taminga16]

Caused by the university joints non linear twisting being out of synch? I've never ever considered that..... Could explain. Some things I enjoy wondered about for years.

Thanks for the insight!

Dann

Hi Dann,
The only university joints that I knew of when your age were either smoked or sat around in playing drinking games and talking politics whilst pretending to be gainfully occupied.
Greg.

[SalonRacing]

I have always marked the orientation of the tailshaft at both flanges and reinstalled it in the same position, I don't know if it makes much difference it's just something I have always done out of habit.

It's pretty easy to drop the tailshaft and check the UNI joints on the tailshaft but it would appear that you can't replace them anyway and would have to buy a new tailshaft, you can try lubing them up but it would be a temporary fix.

I really doubt your brother did anything to your car but feel free to guilt him and give him sh*t.

[Mr Morlock]

whining noises are usually bearings - gearbox or diff and you need to take it to a mechanic and get an opinion. We have no history of the car - has it done 20K or 200K. The change the oil thing is usually too simple if its making a noise then a bearing is probably damaged. Forget diy unless you really know what you are doing- you cannot learn about cars by reading a few paragraphs on a forum.

[pcmx5]

I replaced a tail shaft at around 80000 klms because it had worn uni's and was causing vibration.Did some research and a few specialists said it was common (including a guy,Gibson I think in Newcastle,)Had a new shaft made up with replaceable uni's here in Geelong at around half the cost of a Mazda one.I also had a bit of a whine on over run which disappeared.

Peter.

[revhead]

Yeah I changed the oil and the nylon bushings and wave washers in the turret at the same time. The noise doesn’t sound like its coming from the diff but I will have to change the oil in that soon, just been lazy lately. The noise seems to come from between the driver and passenger seats, if not a little past it toward the rear. Only happens after a while of driving too which is odd.. And only in 3rd and 4th gear.. Car has done 170,000ks, previous owner said the clutch had just been changed too, feels new as the bite point is very low on the pedal and feels good. i noticed when I push the clutch in while the noise is happening it goes away??

[bruce]

Don't be amazed if there is minimal oil in your diff. These things happen.

[aka_juffa]

The noise seems to come from between the driver and passenger seats, if not a little past it toward the rear.

As the noise is gearbox, tailshaft, differential related it is being transmitted through the opening in the chassis/floor pan where the gearbox turrent sits. Or at least that is my experience.

I have been frustrated in the past looking for rattles/squeeks under the dash, only to find the cause was in the engine bay.

J.

ps I also have personal experience where upgrading an NA6 open diff to a NB torsen limited slip diff made the whine go away. I put this down to the thick rubber 'isloation pad' that sits between the drive shaft and the diff on later model 5s.

[revhead]

ahh i see what you are saying juffa, thanks. i will check out the diff oil asap. was just out for a drive then, was on the road for about 30mins just regular driving, didnt hear the noise. i think it might be related to when i go on THOSE drives that involve me using the full potential of the mx5 such as a cruise night. might be the diff heating up to the point it makes that noise, but again, only in 3rd and 4th, very rarely second.