Gillesper

Birdie: I posted a video below, I'm not talking about the about to stall chugging that happens. It will happen when I engage the gas under 3k RPM. I'm not having this issue when driving aggressively. This is more when I'm pulling out of my street to get up to 45 mph on the blvd and shifting gears between 2-3k RPM. If I keep it below 2k RPM I can keep it pretty smooth, but that's just because there isn't much power happening so the bucking is just not noticeable. Hopefully the video gets us some clarity.

Rochester: Thanks! I'll check out the spring.

Jsolo: Thanks for your insights here! I'm having the opposite problem. I'm getting slop when not driving aggressively. As far as grabby vs bucking. Grabby to me is when you let out the clutch too fast and the car kinda bounces really quickly to adjust. This is a rhythmic 1, 2, go, almost as though something is lopsided or loose. If you told me I one side of my transmission mounts are broken, I would believe you. I don't know enough to determine what exactly it is, or what not enough clutch material, or what a bad flywheel feels like. All I know is that it seems like something is wrong, I'm trying to first understand if that is a correct statement or not, if so, where to focus my attention on and what exactly to ask the shop to look at so that I'm not blindly throwing money at this thing.

Thanks for all your help!

Gillesper

Next time I have it in the shop I'll check this, thanks!

My intuition is that it's not the suspension. The suspension feels great, so I'm not thinking it's that. If you were to tell me I had one side of my transmission mounts down, I could get on board with that. But in the PPI both mechanics said the car looked really good, no mention of any mount issues.

When I'm having the issue, I'm not accelerating quickly. I am accelerating normally onto the blvd to get up to 45 mph under 3k rpm, I'm getting the bucking. It's hard to capture that on camera, but I'll try. In the video, the biggest tell of the bucking is the noise, which is why I was accelerating as quickly as I was. I'll see if I can get a video today, maybe hang something from the mirror to show the bucking when driving normally.

As far as determining the clutch material left, it's my understanding the mechanic did it by feel. But I'm not having any slipping issues so I'm thinking it's good to go.

Rochester

iTrader: (9)

You only have the one transmission mount, in the middle, under the transmission. You're probably thinking of the engine mounts. Either way, aren't all three mounts fluid filled, like the main diff mount? Maybe one is blown?

Even when my car was new, and before the short rear gears, the only thing 1st gear is good for is rolling (or launching) out of the hole. It's just not any good for for maintaining speed, no matter how slow. So maybe there's a little bit of driver issue here too.

Birdie

Is that a popping noise when you are letting off. ? Almost sounds like it is your diff bushing

RobC7

^This.

I recommending getting the Bell Racework differential brace. About 15mins to install and it made a big difference on the drivetrain slop.

JSolo

iTrader: (14)

Based on the video, the noise doesn't happen immediately, but slightly after throttle is applied. If diff bushing I'd expect an immediate clunk, no?

I think the best bet is to take it to someone who has a clue, drive the car with them, point out of the concern. If who ever did your PPI doesn't consider this to be an issue, find a different mechanic.

Rochester

iTrader: (9)

I wouldn't recommend installing the Bell diff brace as a fix for bushings are blown or weak. That's not what the brace is for.

Gillesper

The PPI revealed a small leak in the rack & pinion and a busted rear differential bushing. I had the rack & pinion & rear sub frame replaced under warranty.

Is there something in the fuel system that would cause inconsistencies when initially pressing on the throttle, or releasing the throttle? It works itself out above 3k RPM, but the bucking happens when pressing on the throttle, as well as when letting off the throttle (less so but it's still there).

I've been looking for someone who knows manuals, let alone this car, to take a look at it and diagnose. No luck yet. Does the forum have any recommended shops in Southern CA? I asked the dealership and they what $250 to diagnose when I'm not sure if there's an issue or not.

Birdie

Is there something in the fuel system that would cause inconsistencies when initially pressing on the throttle, or releasing the throttle? It works itself out above 3k RPM, but the bucking happens when pressing on the throttle, as well as when letting off the throttle (less so but it's still there).

Nothing in the fuel system that would cause that that I know of.Maybe in the throttle body itself but that would only affect acceleration and would not have anything to do with letting off to cause that bucking your describing. The only thing that comes to mind would be dirty maf sensors to when you let off the accelerator the car is not reading the air coming in properly and giving you a bad mixture.

I asked the dealership and they what $250 to diagnose when I'm not sure if there's an issue or not.

I would wait to see if the new subframe makes a difference before looking into any issues. Sometimes the things that are causing issues have nothing to do with what is causing them (not sure if that makes sense but I have heard of the weirdest fixes)i guess what I'm saying is fix the things that you know are messed up before moving foward.

spoolin03

I remember driving a manual g37s coupe and I could not get the damn thing to engage smoothly no matter how carefully I was modulating. It's a real **** because there's a little trick to it, you have to be soft and fast.

22BR

I bought my G37 sedan used with 70,000 miles. It seemed a bit challenging to achieve smooth starts/shifts (especially compared to its predecessor, a BMW 330) but I eventually got it worked out. However, as colder weather appeared I discovered the clutch MC was leaking internally and causing the clutch to barely disengage at full pedal depression. A new clutch MC fixed that problem and actually improved the shifts between all gears -
I didn’t realize how bad it was since I had not experienced the deterioration over time.