Guessed

I bought a G37 Journey Sedan 2WD, Liquid Platinum with 17 K miles in February and I'm loving it. It gets great mileage, has explosive power, and after changing the Y-pipe under warranty is a very smooth and quiet ride.

Now, here's the fun part: like many G37's, it rumbles a bit when standing still with the transmission in drive, like at a red light. So at lights, I'll shift into neutral, which greatly reduces the rumble to a level normal for a V6 with this much power - about the same level of subdued rumble as my Z06 had.

I have spent months Googling G37 idle noise, rumble, vibration, etc., and read all about throttle body cleaning, idle relearning and reprogramming, software updates from Infiniti, Y-pipe issues, exhaust system leaks, vacuum leaks, rattling heat shields, bad engine mounts, alternator and other belt resonance, weak battery, and so on, but I have not read anywhere about solving the problem the way I described it above: by shifting into neutral.

Well, "solving" isn't exactly accurate. It's a work-around. The right solution would be to be able to have the same smooth, rumble-free idle when not moving and with the transmission in drive - like most cars that are cheaper, or more expensive, or American, or European, etc. Of all cars, why does the "luxury division" of Nissan program a G37 engine and transmission arrangement that results in this pervasive, almost signature rumble. "They all do that" - yes, I got that from my local Infiniti service adviser as well.

But wait, there's more. When shifting from drive into neutral, the rear of the car shifts up! Basically, the torque from the engine has been unloaded from the tires. Going back into drive, with my foot still on the brake, the rear hunkers back down as torque is re-applied to the tires - and of course the rumble resumes. Basically, the rumble is no mystery. I could probably make many cars rumble if while standing with my foot on the brake I slightly nudged the accelerator pedal while the transmission is in drive, which of course for rear-wheel drive cars would also make the rear hunker down a bit. It's your classic brake stand, without actually going ape and spinning the tires.

So, the bottom line is, the transmission is slightly too engaged when in drive and the car is not moving. It's like I'm permanently about to drag race somebody when the light turns green. What I'd like, what I think would be smart after the warranty expires, is a bit more transmission disengagement under stationary conditions in drive, to primarily stop the premature wearing of transmission surfaces and premature aging of transmission oil, if not the annoyance.

Anyway, to make a long story a bit longer, I did do the idle re-learn, but it did not help the rumble. The idle is steady between 600 and 650 RPM, and the re-learning did eliminate the 200 to 250 RPM idle surge that an unlearned computer can produce under fluctuating environmental conditions and turning on and off accessories, like AC.

What I don't want to do is have Infiniti service blindly throw the book at my car and flash all sorts of computer updates - and then possibly not solve the problem while potentially introducing new ones. I don't have bothersome gear hunting or hesitation, and acceleration is predictable, and many service bulletins affect these parameters of drive-ability.

What I would like is just a surgical reprogramming to reduce the amount of transmission engagement while standing still in drive.

Did I mention I still love the car?

Has anybody experienced this or have had Infiniti solve this overly aggressive power transfer while idling?

*shifts into neutral*

hechen507

iTrader: (5)

What kind of mods have you done?

Guessed

None. She's stock.

hechen507

iTrader: (5)

I had the same exact issue for 2 years. I would ask the dealer/shop every time I had a visit. Most of them had no clue. I even had my tuner adjust my idle RPM while in drive trying to fix it, but the problem persisted.
With some experimenting while putting my car in drive and having the e-brake on, I looked under the hood and eventually found my issue. It was my intake making contact with chassis.
Maybe you have a similar issue.

Guessed

That's the first time I heard or read about this! So what you are saying is, in gear your intake and chassis contacted, but in neutral they didn't? I'm going to check my clearance.

I appreciate the feedback!

hechen507

iTrader: (5)

Yep, however I have a Stillen Gen3 intake. You might have the same issue with other components. If you start noticing the rumbling, put your car in drive and ebrake on, get out of the car and start pin pointing out the source.

Guessed

Well, there's no chassis contact. That leaves me with my theory that when shifting from park or neutral into drive - with foot on brake so the car can't move - the rear immediately hunkers down about half an inch, a clear sign that too much torque is being transmitted to the drive shaft by the automatic transmission, and of course, the muted engine rumble becomes loud, the driver's seat seat vibrates, and sometimes something in the dashboard starts buzzing. Then, slipping back into neutral, the rear unhunkers, lifting back up half an inch to the car's neutral resting position, and the rumbling, vibration, and buzzing subside.

My conclusion remains the same: when standing still and shifting into drive, the computer is instructing the transmission to transfer too much torque.

Maybe a transmission fluid flush and refill could solve the problem?

I'm about to give up and head into Infiniti. It's still under warranty for another 9 months.

Magicmets

Im having the same problem, did you ever find a solution? Thanks

slartibartfast

iTrader: (7)

Check diff mount for ruptured bushing. Make sure exhaust is not touching the stamped cross-member. Check that trans and engine mounts are in good shape.