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Discussion Starter · #1 ·
Has anyone figured this out?

I couldn't figure it out at first when I got the grind until recently. I have a fast off ramp that I end up in 2nd and then at speed by the time I merge so I just go 5th / 6th. Any other car I have had there (a 1996 Saturn SC2, a 1998 240SX SE, a 2006 BMW M3 ZCP) did this shift just fine.

My Mazda ALWAYS grinds a little. It's easily reproduced by hitting 5K or more in 2nd gear and shifting into 5th or 6th. Double clutching doesn't solve it.

The dealer is willing to verify and will write up a transmission if they can duplicate it. I don't want to go through getting a new tranny only to have this be normal. I have seen other posts on this.

My car is a 2012 s Grand Touring with 24k on the clock.

Thanks!
 

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I never do that. I might jump 2nd to 4th, but definitely not to 5th or 6th. It's probably that the synchros are not set up to mesh like that.
 

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Why in the H would you shift from 2nd into 5th at 5k rpm? ...you need to get an automatic. :no:
 

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Depending how you move the lever, I'd guess it's a similar issue to the Honda K-series transmission. On Si's you can grind the 2-3 shift if you don't move the lever distinctly up-right-up, and in your case the 2-5 shift is even farther to the right. Perhaps you're not going all the way over before trying to nudge he lever up into 5th.
 

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It's definitly a syncho thing but if it's the car or the driver's fault that's the mystery. Color0 has a good point. Try it for fun.

Perhaps you're trying to shift too fast and it doesn't line up like it should. I would think that the timing between positioning the shifter in gear and de-clutching has something to do with it. You may be used to letting the clutch go just in time and you are accustomed to it working great so when you travel over a few higher gears you may doubt that your are in 5th or 3rd or you may not be used to the trajectory and de-clutch anyways causing a slight delay in positioning the shifter fully in gear thus letting the clutch go slightly too early making the synchos grind gears.

In this case, doubt, hesitation on the trajectory plus routine shifting habits would be the cause. Human mechanical memory can be a bitch to work with sometimes. Especially if you depend on it too much when attempting to do something new.



I never do that. I might jump 2nd to 4th, but definitely not to 5th or 6th. It's probably that the synchros are not set up to mesh like that.
I do it all the time. No issues. 2-5, 3-6. Just don't hammer down once you're in the higher gear.
 

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On that college budget
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Got to shift slower, it is a syncro thing. I do it sometimes when I need to accelerate real quick then I dont need to anymore.
 

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You know the easiest fix would be to shift normally lol

You cant expect the trans to perform normally when its being used abnormally. Shift forks/linkages prefer to be moved in order since thats how they are designed.

If youre going from 2-5 try shifting through 3-4 while the clutch is still disengaged to see if that helps. Not only will it line up the linkage but it will give the synchros some time too
 

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Discussion Starter · #9 ·
It would be nice if everyone read my post fully.

It doesn't matter if I shift slow or not, I can even double clutch and it happens. I have read that others have this same issue. It's going from a high rpm 2nd gear shift (like when trying to merge) into 5th or 6th because now you are in that rpm range.

Manual Transmissions are not made so you have to go 1-2-3-4-5-6. The whole purpose of a manual is to be able to select a gear (throwing out the idiots that will bring up reverse) and if the driver is wrong then an overrev or stall condition can occur.

I have driven a manual transmission for nearly 25 years now. It's not my error. I was willing to say that myself being it was a new car 25k miles ago, but it's definitely not me hitting between the gates or not having the clutch fully depressed or trying to gun it right after the shift.

In fact so far others have been able to duplicate this on theirs. Just take 2nd gear to 5k+ rpms and shift to 6th. It will happen every time in my case.

None of my other cars did this (86 RX7, 88 Mustang GT, 89 Mits Precis, 97 VW GTI VR6, 96 Saturn SC2, 98 240SX SE, 06 BMW M3) and no car should.
 

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All cars are not the same. You say no car should do what yours is doing. So why are you asking a question then? Apparently you already know it shouldn't do it so go to the dealer and get your tranny replaced.
 

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Going from 2nd at high RPM to 5th is overwhelming the synchros as they have to spin the clutch plate down a few thousand RPMs to get the teeth to mesh up. Depending on the design of the tranny/synchros, the mass of the clutch pressure plate, and the RPM difference between gears, any manual tranny could do the same on such a shift.

To avoid it, drop it into 3rd or 4th momentarily before shifting into 5th. Spread the work out across a few more synchros.
 

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Discussion Starter · #12 ·
All cars are not the same. You say no car should do what yours is doing. So why are you asking a question then? Apparently you already know it shouldn't do it so go to the dealer and get your tranny replaced.
Because if you search for this issue others are having it. I don't want to have a tranny replaced to just have the same (and now probably other issues) from it.
 

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Discussion Starter · #13 ·
Going from 2nd at high RPM to 5th is overwhelming the synchros as they have to spin the clutch plate down a few thousand RPMs to get the teeth to mesh up. Depending on the design of the tranny/synchros, the mass of the clutch pressure plate, and the RPM difference between gears, any manual tranny could do the same on such a shift.

To avoid it, drop it into 3rd or 4th momentarily before shifting into 5th. Spread the work out across a few more synchros.
The synchros do nothing to the clutch plate. There are brass clutches inside a transmission if that is what your are referring to, but those don't get slowed down either by them.

Apparently, what's happening is our synchos can't keep up so the gears aren't meshing equally.

My hope was other's tried this to verify here, as everywhere else it seems this is the case with everyone of these cars.
 

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The synchros do nothing to the clutch plate. There are brass clutches inside a transmission if that is what your are referring to, but those don't get slowed down either by them.
The synchros get the input side of the transmission into into sync with the output side so the teeth can engage. To do this, it has to either slow down (on upshift) or speed up (on downshift) the input shaft which is connected to the clutch plate. Thus, the clutch rotation also changes when you shift gears (this is why you have to disengage the clutch to shift properly, so the speed change can occur smoothly).

When doing a large jump in gears such as 2nd to 5th the synchros (which are the brass clutches you're referring to) have to make a large change in speed to sync the gears, and if they can't quite do it by the time the teeth start to engage, you get the grind.
 

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I agree with kpatz and I really don't understand the reason for this post. Are you trying to get others to duplicate what you are doing so you can prove that the car has a badly designed tranny or are you trying to prove to the dealer that no one else has this problem so that they will replace your tranny?

What speed are you going at 5k in second gear, about 30-35 mph, and why would you have to skip up to 5th or 6th gear, it just doesn't make sense to me. I've driven manuals all my life too and if I'm accelerating fairly hard, 5,000 rmp is up there pretty good in 2nd, I would shift into 3rd and keep accelerating. If I wanted to let off on the acceleration I might shift into 4th, but why shift into 5th or 6th directly? If you were going 70mph in 6th your rmp would probably only be about 500 or so.

Maybe I'm just missing your point.
 

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oh did this today going to the store, 5k 2nd gear like 40-45mph. into 5th just a slow shift not a speedy shift, and no issue but it felt so unnatural. 5k to 2kish rpm.

now i have grinded gears a few times in this car. but i didnt do it the twice i tried this. but like i said i was letting the rpms drop as i slow made it over to the gear.

i have had to alter my driving habits alot with this car. my last truck( that i could drive fast) was a 4cyc with cam and a 11lbs fidenza flywheel, add in a shift sifter and yiou could shift as fast as you wanted. the motor would out run the tach if you just reved it.


my main question is why? why are your reving to 5k rpm then hitting overdirve?
 

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Discussion Starter · #17 ·
I agree with kpatz and I really don't understand the reason for this post. Are you trying to get others to duplicate what you are doing so you can prove that the car has a badly designed tranny or are you trying to prove to the dealer that no one else has this problem so that they will replace your tranny?

What speed are you going at 5k in second gear, about 30-35 mph, and why would you have to skip up to 5th or 6th gear, it just doesn't make sense to me. I've driven manuals all my life too and if I'm accelerating fairly hard, 5,000 rmp is up there pretty good in 2nd, I would shift into 3rd and keep accelerating. If I wanted to let off on the acceleration I might shift into 4th, but why shift into 5th or 6th directly? If you were going 70mph in 6th your rmp would probably only be about 500 or so.

Maybe I'm just missing your point.
First, the dealer will replace the transmission. I don't need to prove anything to do that.

I was hoping others would do my scenario and report back. It's apparently a poorly designed transmission.

For my situation it's a hot off ramp that you have to get moving. I end up in 2nd, I don't know the speed other than it's about 5krpms. I put it in 6th because then I am cruising again.

I drive 2000 miles or so a month, a lot of it constantly shifting up and down on I95.

The whole thing though with having a manual is choosing the best gear to go into. That gear is usually the highest that doesn't lug the engine if you are still not trying to accelerate.

Saying one's whole life here doesn't mean much without qualifying it. I am sure many have been driving less than 10 years here. My first and only auto was my first car. A fully restored 66 Mustang GT, after that it's always been manuals and most I have always been able to go 2-3 into 5-6 after I have gotten on the highway. Sure on the track I am more linear and always with the quarter mile. I forgot I also had a 92 Acura GSR above. I have had a lot of cars.

The Mazda 3 was not my choice of cars. My ex-wife liked it because it was 'cute', I gave her a $30k cut off budget. In my divorce my M3 had a ton of equity. Her Mazda 3 did not. She wanted to pay for it herself so wanted a 72 month loan. I made every payment...now I am stuck with it for a couple years as I rather not just sell it at a loss and it's not a terrible car. Just not up to the same standards as I have been used to.
 

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Discussion Starter · #18 ·
oh did this today going to the store, 5k 2nd gear like 40-45mph. into 5th just a slow shift not a speedy shift, and no issue but it felt so unnatural. 5k to 2kish rpm.

now i have grinded gears a few times in this car. but i didnt do it the twice i tried this. but like i said i was letting the rpms drop as i slow made it over to the gear.

i have had to alter my driving habits alot with this car. my last truck( that i could drive fast) was a 4cyc with cam and a 11lbs fidenza flywheel, add in a shift sifter and yiou could shift as fast as you wanted. the motor would out run the tach if you just reved it.


my main question is why? why are your reving to 5k rpm then hitting overdirve?
I don't think the skyactiv's have this issue. It seems to be the 2.5L 6MT.

When doing this scenario, I go to 5K, put the clutch to the floor and can either slowly shift and verify I am in 5th or 6th and then release the clutch and get the problem (by this time the rpms have fallen). I can even double clutch in between and it will grind. It's like the transmission internals aren't slowing down fast enough.

It may be just something I need to get used too.
 

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So, from what you said above, "It's apparently a poorly designed transmission." you are just trying to get others to go along with your view... why?

Maybe you should just shift into 4th instead... what is the big deal?
 

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I'm with doane. You know it's a limitation with the trans, so really, now that you've confirmed it just go deal with it. Drive around the problem or engineer a solution yourself, which would be marketable to anyone who also experiences the issue.
 
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