My car was in for its first service today and despite all the horror
stories I’ve heard, I have to say it was a pleasant surprise.
I mentioned the widely reported transmission chatter on taking up
drive and up to about 2000 rpm, not because I was particularly worried,
but because I wanted it recorded in case it developed into a problem.
When I collected the car, I was given an information sheet -
Technical Bulletin No NC/008 Section No J/001 for MX-5 (NC) with manual
transmission dated 7th July 2006 (I’ll scan it and try to post it
tomorrow).
Basically, what it says is that the noise is “backlash noise”
resulting from the play in the transmission which is necessary to
prevent seizure. The lightweight flywheel and the rigidity of the
powerplant frame effectively amlpify the noise. All this is what I
expected.
The important part is this - they have carried out a modification to
reduce the backlash noise as much as possible - this comprises fitting a
“special spring” to the clutch to attenuate engine RPM fluctuation and
adding a dynamic damper to the differential to “reduce the level of
noise when the gears hit each other in the manual transmission”
It certainly seems to have worked - the chatter is still present, but
it’s very much quieter and less harsh. It’s barely noticeable now.
So, if you have a chattery transmission, get along to your local dealer and tell them about the bulletin and the modification.
I read the above with interest as I have a Launch Edition NC which
has a bit of “backlash noise” so I thought I would pop into my very good
local Mazda dealer, Mitchell Mazda nr Chester, to ask them about it.
They were, as usual, very helpful and found the bulletin in question and
showed it to me.
The top and bottom of it is this; the subject is “Backlash noise from
manual transmission” and is “material for explanation to customer”. It
explains why there is some noise from the transmission and (essentially)
what Mazda has ALREADY done about it during manufacture. They also
state that their competitors sports type vehicles also experience
similar noise.
They have, as OchAye has already stated, added a “special” spring to
the clutch and a “dynamic” damper to the differential in order to reduce
the level of noise when the gears engage. This has already been done
and there are no parts to add or renew in connection with this bulletin,
it is for information only when customers bring up the subject of noisy
transmission. It is, apparently, normal.
Personally I’m satisfied with this explanation and Mitchells have
always been honest with me and I have an extremely good relationship
with this dealership. The noise is part of the nature of the beast and
unless it is extremely excessive we have to live with it. The noise on
mine doesn’t impair the enjoyment and I wouldn’t have made anything of
it if it hadn’t appeared on the forum