Gillesper

Hey all! Newb here trying to work out the kinks with my 2009 G37S 6MT Sedan with 93k miles on it. It seems to be the most finicky stick shift I've ever driven and I was hoping to get insight as to why. I've driven stick on a Mustang, Mazda 3, WRX, and Audi A5, all of which were very easy to drive smoothly, but for whatever reason, this G37S is so damn finicky! I had two PPIs that showed the car was in great shape, never throwing a code in it's life, and just clean overall. They said there's at least 50% of the clutch left, and I'm not having any grinding or slipping issues. I'm trying to figure out what's going on with standard drive of it. When I engage the gas, the car kinda lurches twice then gets going. When not shifting, it's very subtle, but it's there. When shifting though, it becomes very apparent. Gears 1-3 will buck after letting out the clutch. It's not a lurch like when letting out the clutch while the RPMs are too high, and it's not a chug, like when letting out the clutch when the RPMs are too low. It seems to be an engaged buck, buck, go. It is very annoying for my wife who wants me to get rid of the damn thing! I'm thinking there has to be a fix.

Two observations:
1. The clutch engagement area is very small, especially when considering how far the clutch pedal travels.
2. This only happens when the car is being driven easily (below like 4k RPM). They car drives best when absolutely hammering it.

What do with think this is? I'll see if I can get some video of what's going on.

Thanks in advance for your help!

Chad

Rochester

iTrader: (9)

Hi Chad. Welcome to the forum.

IDK about your bouncing around, however the OEM clutch pedal behavior is exactly what you're describing. There are two solutions: replace the return spring with a softer spring (good, cheap fix), or replace the entire clutch pedal assembly with the RJM pedal (best, more expensive fix).

https://rjmperformance.com/370z-g37/

Gillesper

Thanks Rochester! Just went down a few hour rabbit hole on your threads! What did you come up with after all the adjusting? Did you get a lower engagement point? Is 100% still pretty stiff? I don't want to make it any stiffer, and I would love to get the engagement point closer to the ground. I'm not sure if you did that, but if the engagement point isn't closer to the floor, how does this mod smooth things out? Between you and Furlow this seems like a no brainer, but I'm not understanding what will change and how the drive experience gets better. Will you explain?

Thanks!

Rochester

iTrader: (9)

It's been so long ago, I can't really describe it well enough because I've lost my point of reference. Sorry.

If this is the first time you've heard about the RJM pedal assembly, all I can say is this is a must-have mod for the G/Z 6MT. It's not terribly expensive, and is pretty much a DIY for anyone with patience.

You found my old thread about the pedal, then you saw this image, which is kind of self-explanatory. The only other thing I can say based on recall of the mod is that the RJM is much more analog. By that I mean you "roll" the pedal with your foot, unlike the OEM pedal which is more of an on/off kind of thing. That's why the soft spring mod is so well received, because it let's you control the pedal more. Plus you can position the pedal wherever you want, which is nice. I once drove a modified 6MT where the pedal was close to the floor and dialed in with a low engagement. It was really weird to drive like that, didn't really like it, but clutch operation sure was quick.

Get the RJM pedal and a short-throw shifter, and you will always enjoy rowing through the gears on this car. Stock for both these parts is much less rewarding.

And while all that might be true (it is), it doesn't address this "bucking" behavior you're describing. Don't know what that is. Good luck with that.

Birdie

Is this your first manual car owned? Sounds like you just might be engaging the clutch too quickly. Releasing the clutch pedal too fast. All cars are different and drive differently especially on manuals. Try taking a bit more time on releasing the cluth pedal. I'm sure you will get the hang of it.

Gillesper

I didn't see this image in the thread, but it is super helpful, thanks! This is exactly what I was looking for. I'll look into both these mods. Thanks for your help here! Did you get a weighted shift **** to go with the short throw? Is that the final piece of the puzzle?

I'll pose the question to you and Birdie as well. When you are in gear, let's say 1st gear, let off the gas to come to a crawl, then press on the gas again like half pedal, does your car accelerate smoothly up to like 10 mph? Mine "bucks" even when engaged. So the bucking seems to be accelerating at low RPM, then when I add in a less than ideal clutch release, it really makes the bucking pronounced. It will buck twice, then be smooth all the way through the higher RPMs.

Gillesper

Hey Birdie. Yes, this is the first manual car that I have owned, but I have driven many hours of stick shift in cars that I don't own. It does sound like I'm letting out the clutch too quickly, which brings me back to the OEM engagement, and how high up the pedal engages like Rochester mentioned above. I'm used to the clutch engaging closer to the floor, so I can pivot off my heel on the ground. But when it engages so high, my heel is off the ground, and it's more difficult to control. Since it's been 6 months and I'm still trying to get a hang of it, + the bucking that happens when the clutch is already engaged, it makes me think something else is going on. So I'll pose the question to you that I posed to Rochester.

When you are in 1st gear, let off the gas to come to a crawl, then press on the gas again like half pedal, does your car accelerate smoothly up to like 10 mph? Mine "bucks" even when engaged. So the bucking seems to be accelerating at low RPM, then when I add in a less than ideal clutch release, it really makes the bucking pronounced. It will buck twice, then be smooth all the way through the higher RPMs.

Birdie

The g is somewhat of a heavy car so it will take a bit more feathering to get it going . I believe if you coast any car down to idle and then get on it it will buck or jerk a bit before it gets going. So yes to answer your question my car will do this even though I do not have the factory heavy dualmass flywheel. Kinda like being in a high gear with low rpms, the car is going to want to stall. Either you can press in the clutch while coasting and drive it like you are taking off from a complete stop (my personal favorite, no jerking) or lightly stay on the gas pedal while barely moving. That may be a bit more difficult. I dont think any mod will help as much as your own driving style.

Rochester

iTrader: (9)

I can't say how much of this is the car or the driver. For as long as I've owned this 6MT (nearly 10 years now), there was this shudder after shifting lower gears and letting off the throttle. I always blamed myself instead of the car. I mean, I've been driving manual transmissions for 40 years, but that doesn't mean I'm any good at it. Anyway, after getting tuned this Spring, that shudder went away. Here's the thread:

https://www.myg37.com/forums/ecu-tun...e-project.html

My summer shift **** is 450 grams of solid titanium. Not overly heavy, but I love the feel and the shape. My winter shift **** is made of Copolymer, because winter. Here's my old thread on the STS and the transmission mount:

https://www.myg37.com/forums/drivetr...ion-mount.html

Birdie

[QUOTE=Rochester;4302269]I can't say how much of this is the car or the driver. For as long as I've owned this 6MT (nearly 10 years now), there was this shudder after shifting lower gears and letting off the throttle. I always blamed myself instead of the car. I mean, I've been driving manual transmissions for 40 years, but that doesn't mean I'm any good at it. Anyway, after getting tuned this Spring, that shudder went away.

I can see the tune getting rid of that shudder problem. Our cars usually idle at about 600 rpm. Tuners usually set the idle a bit higher maybe 800 to 900 just depends. Not sure if this is your case Rochester but that's the second driving style I was mentioning about just giving the car slight gas while coasting. The higher idle is just enough to keep it out of the wierd driving state. The other lower gears are are just the extra power you got from the tune that keep it from doing that anymore.

Now I'm curious to know what the OP car idle at vs Rochester?

Rochester

iTrader: (9)

My idle RPM wasn't changed. So...

Birdie

Interesting ....

JSolo

iTrader: (14)

To the OP,

I think part of the issue is driveline lash. That is, slop in the diff and trans. Most noticeable when aggressively on/off throttle transitions. Somewhat remedied by easing off, easing on the throttle.

I noticed this immediately (or lack there of) when driving the new car on some challenging backroads. I could easily transition on/off throttle smoothly.

As for the G, at times stuck in traffic, I could putt along slowly in 1st or 2nd gear with no throttle, just idle. No bucking. However, applying throttle had to be progressive so as not to jerk the passengers or myself. Short of pulling the pressure plate, how can a ppi determine how much clutch material remains and its condition?

Do you think rather than calling it bucking, maybe a better term would be grabby?

Gillesper

Hi All, let's see if this works. I think there are two problems going on, the clutch portion of things (user error?), and the bucking portion of things (TBD). Which together, make for an uncomfortable ride. Check out this video. This is in gear, simply accelerating from 10 mph in first gear, pressing about half way down on the gas pedal, and the car bucks, or lurches, twice. It's hard to capture on camera, but you can hear it best in the second run. It normally smooths out above 3k RPM. I think this is why it's comfortable to drive hard (always above 3k RPM), but really uncomfortable when driving normally (below 3k RPM). This test should show what happens when we take the clutch variable out of it. What do you all think?

JSolo

iTrader: (14)

Can you jack up the rear to test for how much play is in the drive line? Once in the air, put it in first and just rotate the wheels back and forth. Is there a little movement or lots?

It's hard to tell from the video if the issue is driveline related or suspension. It makes sense this would present itself more so at lower speeds than higher as there's more torque applied when taking off (larger gear ratios at play).

What happens if you apply the throttle more slowly the lower gears?

All mounts (engine/trans) secure?