adrien

Hi guys --

Just noticed this on my 8...haven't noticed it before, but that may be because I usually have the radio on.

On a downshift into second (from 3rd or 4th or any other gear), I notice the syncros seem pretty loud. I put in the clutch, drop it into second, rev the engine to match and then let out the clutch. The noise I hear sounds like something speeding up (I'm guessing the syncros) while the clutch is still in. It doesn't seem to do it as much in any other gear.

So...so any of you have the same thing? Is this something wrong, or is it just a noisy transmission?

adrien

anyone?

Did some more experimenting on the way home...double clutching makes no difference, so it's not the syncros...but it only makes the noise shinfting into the gear when downshifting from a higher gear.

Anyone? Bueller?

nt5k

1. What kind of car did you drive before this?

2. Did you try rev-matching?

3. You're pretty much sitting on the transmission, it's going to be noisier than cars where the tranny is in lala land..

Kwullen

Second gear synchros get lots of abuse, so I think Mazda probably put in a pretty stout one. Mine is a little more noticable in second, but I seldom down it into second without double clutching/rev matching it. Just habit from having so many used cars with second synchro in bad shape when I bought them.
BTW, my 8 is my FIRST brand new car and I'm 53.
I've always let someone else eat that first year or twos depreciation. I guess I'm gettin impatient in my old age.

w2aew

It's not the synchros you hear, but rather the input shaft/bearing of the transmission. When down shifting, you are asking the synchros to spin up the input shaft and clutch disk, and it's that spinup that you are hearing. It's normal. If you slow down a little more before downshifting, it won't have to spinup as much and won't make as much noise. As previously stated, the transmission sits up higher and deeper into the passenger compartment that most cars (due to the fact that the output of the rotary comes from the center of the engine, not near the bottom), and the doesn't have a ton of sound deadening material (why waste the weight). The sound is normal, part of the lure of a sports car...

adrien

Hi guys ...

Nice to know someone's out there.

I always rev-match on downshifts. Driven manuals for 20 years, including a Miata for 5, and integra gsr, various Hondas and Audis.

Shaft theory makes sense, as does the idea that 2's syncros are stouter.

Thanks for the replies.

sferrett

Both my other rx7's make/made a similar noise when you're downshifting and the susequent engine speed is going to be relatively high - it's most noticeable in 2nd and especially 1st. My Jeep which is also a stick does it as well but it's not as loud (it has other louder noises which mask it out..!)

I think it's completely normal.

Simon.

Haze

That's why you bought a performance car! Triple cone synchros in a small lightweight transmission that you are sitting right next to with so little insulation that it roasts through the console. My car makes the same sound, and I love it. It is similar, though louder, to the sound that the trans in my Alfa Romeo sounds. It's the sound of the input shaft, the lay shaft, the synchros, everything pinning that you hear, and remember that in a piston slappin' car, the enghine would be screaming so loud that you would never notice the sound of the transmission. You would be hearing the revving of the engine which in the roatary is just . . . mmmm.

mmmmmmmm

TheColonel

Am I gonna blow my syncro over time by not rev matching? I'm 20 and so I never really learned to drive stick properly, just how to drive it fast.

Kwullen

Yes. There are several threads here about double clutching and rev matching. Also, there's no need for fancy downshifting to slow the car, use the ample brakes, shift down to be in the right gear to speed back up or accelerate through a turn. Learn to rev match and double clutch when you need to go from 6th to fourth or third (more fun!!) for passing. Your box will last a lot longer and make far less noise, over the years.

Check this thread:https://www.rx8club.com/showthread.p...threadid=32345