2014 Mazda3 SP25 GT loose jerky gearbox or drivetrain - Mazda3 Forums : The #1 Mazda 3 Forum
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post #1 of 12 (permalink) Old 08-27-2014, 08:37 PM Thread Starter
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Angry 2014 Mazda3 SP25 GT loose jerky gearbox or drivetrain

Hi all, I wish this wasn't my first post, but I searched but couldn't find anything relevant:

I purchased (on lease) a brand new 2014 Mazda3 SP25 GT (BM5436) a couple of months ago. It has 2,500kms (1500miles) on the clock. Iíve got two large issues with the car. I have the same crazy head unit issues everyone else does, but the MORE important issue which Iím posting about here is the drivetrain.

Iíve been driving manuals for more than a decade. I had a 95 Honda Civic, a 95 Toyota Corolla Sportivo, and a (heavily modified) 95 Nissan Skyline. So I know how to drive manual, I sort of pride myself on smooth gear changes. But no matter how I drive in this Mazda3, itís a jerky ride. Specific examples:

1) More often than not, if I am rolling slowly along in traffic with very little or no pressure on the accelerator, and I press in the clutch, it takes the car out of gear as expected, but it also throws the weight of the car forward a little bit. Enough for the passenger to sometimes gives a funny look like I stuffed up.
2) If I accelerate from a standing start with my foot most of the way down for each gear, and short-shift (ie. Shift up @ 3-3.5k rpm), and foot my foot down on the accelerator quite quickly on each shift, there is a very noticeably *THUNK* somewhere in the drivetrain, like something shifting around. Most noticeable from 1-2, 2-3, slightly less so for 3-4 and not really noticeable for the higher changes.
3) Sometimes when rolling up to lights (out of gear altogether), the moment I stop, I can feel some shift in weight, or a similar *THUNK* to what I get when shifting gears.
4) When taking off from the lights, sometimes in the split second when I let off the clutch (with a normal amount of pressure on the gas to get rolling), I can hear some sort of *CLUNK* noise.
5) Often when rolling fairly slowly in 1st gear (definitely not slow enough to stall), the car will 'kangaroo' along a bit, in fits and bursts, like your feathering the accelerator to make it jerky on purpose.

Annoyingly, these things do not happen all the time. Maybe 60-70% of the time. Iím 100% sure itís related to interaction between engine RPM and roadspeed, as I notice it most:
1) At lower road speeds and with higher engine engine speeds
2) On shifts in momentum of the car (ie. Taking off, slowing down and gear changes)
3) Happens to some degree regardless of whether I drive like a grandpa or wind gears out

I believe there is some kind of looseness/slack in either the gearbox, the drivetrain, the power-transferring front axle, or the mounts holding one or more of these parts of the car are under-specíed in how much torque they are rated to handle. I took a Mazda mechanic for a 10 minute drive (he was only passenger) and drove as carefully as I could, unfortunately, this of course didnít show the problem very well and he said it felt fine to him. I was too worried that heíd say I was driving too Ďspiritedlyí and that was the cause of the issueÖ but it does it even at slow traffic, I just didnít come across that situation in the test. I am thinking of going back and a) testing the demo model again to compare) and b) get the mechanic to actually drive the car and tell me with a straight face that something isnít wrong. My main fear is that the car is behaving as designed, that most people donít notice because theyíre used to clunky cars, and that I might simply not have noticed when I test drove it because I thought it was just me getting used to the clutch in an unfamiliar car.

Has anyone else noticed this issue? It makes rev-matching impossible/pointless (because it throws the car forward so the gear change isnít smooth, then it jerks the car back and forward a bit because of the momentum shift, regardless of the RPM and road speed). It also makes me quite apprehensive of driving in traffic, for fear of giving my passenger the feeling theyíre about to be thrown into the car in front every time I have to stop in stop-start traffic. And WORST of all: makes the car NO FUN TO DRIVE.

Anyone else notice this kind of thing? ATM, Iíve told Mazda Iím working on recreating the fault reliably. The above conditions recreate the Ďroughnessí quite easily, but not ALL the time, sometimes it barely does it and other times the clunk throws the car around so much I want to push it off a cliff!

Thanks for any help/suggestions in advance!
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post #2 of 12 (permalink) Old 08-27-2014, 11:12 PM
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Go test drive another car. See if the problems are there too. If they're not, fight to get the problem fixed. In my experience dealerships/mechanics will do everything in their power to ignore transmission problems because they don't want to take the transmission out without you footing the bill.
My guess is it's not normal.
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5) Often when rolling fairly slowly in 1st gear (definitely not slow enough to stall), the car will 'kangaroo' along a bit, in fits and bursts, like your feathering the accelerator to make it jerky on purpose.
I have this exact problem and it is annoying as hell. Pretty sure it is a motor mount problem but I am too much of a sissy to remove my PMM or TMM to confirm. Also note that if it IS a failed motor mount the dealership may not find it because the failures are frequently invisible unless you physically remove it and look at it.


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post #3 of 12 (permalink) Old 08-28-2014, 10:51 PM
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I only have 300 miles on my i touring manual, but I've noticed some of the issues you've described in 1, 3 and 4. I wasn't sure if it was just the fact that I'm babying the car and I'm not shifting as quickly or precisely as it likes or if there's something wrong. After my break in period I'll start driving a little more spirited and see what happens. After 15 years and 196,000 miles in a Ford Contour SVT, I more inclined to think it's just me needing to get used to a new car. But I'll certainly keep a record of what I experience.
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post #4 of 12 (permalink) Old 08-29-2014, 10:06 PM
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Does the car have a hill start feature? My 3 has an automatic and sometimes at slow speed (stuck in traffic) it jerks along until the RPMs are around 1200 then smooths out. Even on flat level ground. The Mazda tech told me there is a glitch in the hill start system that needs tweaking in the computer and the dealers do not have access to that program yet. I would imagine a manual would jerk even more.
As for the clunking noises I would have to listen to give you more information.
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post #5 of 12 (permalink) Old 08-29-2014, 10:44 PM
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#5 is just how our gearbox and fuel injection is, there's nothing you can do about it.

The other issues....
#1 is normal to me but not really that large of an issue, that really only happens when you quickly transition from power to no power and then all clutch.

The others.. I don't really have an issue with.

This car you just have to really slow with the gear changes, it really doesn't like short quick throw shifts, it likes to hang around which is annoying to say the least.

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post #6 of 12 (permalink) Old 08-29-2014, 11:24 PM
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Quote:
Originally Posted by XCNuse View Post
#5 is just how our gearbox and fuel injection is, there's nothing you can do about it.
Whoa... that is normal? Really? All this time I thought it meant one of my mounts was secretly shot...


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post #7 of 12 (permalink) Old 01-22-2015, 02:39 AM
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#5 can be fixed with stiffer motor mounts.. had this issue with my 05 Mazda 3.. Only thing is you can feel the engine vibration more at idle and some rpms. if you goto stiffer motor mounts.

Check your motor or transmission mounts you could have a defective one.

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post #8 of 12 (permalink) Old 05-14-2017, 05:21 PM
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I have a 2014 with similar "issues" which have now manifested themselves more seriously in a new manner.

When driving above 45mph or so, around 2k rpm, the tires will impart a bit of vibrations into the chassis of the car from a bump or irregularity in the road and begin to make the motor shake ever so subtly. It is barely noticeable to passengers, and it goes away as soon as I press the clutch and let then engine idle down. It will continue after the initial impact which upsets the balance of the motor in the mounts, which I presume to have either gotten torn or gone soft from wear cycles. Loose motor mounts would theoretically not dampen the vibrations inherent to applying torque to the tires, which would allow for an oscillation at the threshold most highway driving is done at (i.e. the fact that you're just barely applying enough throttle to overcome wind resistance, a constant battle between positive torque sent to the road and negative torque sent back to the engine from the road)

I believe from what I have read, that there are 3 motor mounts on this car, 1 passenger side mount (GHR939060A) 1 rear transmission mount (BJS739070), and 1 rear engine mount/torque strut (GHP939040B)

I would most highly suspect the torque strut, as this is the one resisting torsional forces along the axis of the driveline, aka that "rocking" backwards of the engine when accelerating, and the "rocking" forward when engine braking. I know CorkSport has a replacement that's much stiffer, but that may increase NVH for some people too much. The other option, if this isn't resolved by a fresh factory motor mount, is to fill the voids with silicone/rtv to stiffen them slightly.

I will be taking it to the dealer under warranty and having them inspect all motor mounts during the next oil change and will report back if they find anything. If not, I'll crawl under myself to see if they lie
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post #9 of 12 (permalink) Old 11-13-2017, 09:48 PM
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I just bought a brand new 2017 Mazda 3 GT with a manual transmission and I am experiencing the same symptoms described above 1 through 5. I went to my local dealer and the service advisor told me it is normal, I don't see any problem with this vehicle. I am frustrated with this situation. My car has less than 400 miles and I am already thinking about selling it.
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post #10 of 12 (permalink) Old 11-13-2017, 10:03 PM
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Hmmm, we have a 2016 Mazda3 s GT 5-Door 6-Speed manual and have no such issues; it is very easy to drive smoothly. Then again, maybe it is because it is such a challenge to drive my much higher strung TL smoothly and in comparison the Mazda is a piece of cake.

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