Shaking accelration and deceleration
 

Hey all, 2011 G37s six speed. Recently I’ve been noticing when moderately to heavily accelerating in lower rpms, my car will thud and shake once then start to accelerate.
I hit some back roads, over the weekend, and really got a chance to stretch the cars legs. I noticed when in high rpms and letting the car engine break, the car would this and shake as well.

The car was at the dealer last month and with the milticheck inspection, the motor mounts and transmission mount are apparently ok.

I currently have the Z1 poly diff mount. Mods are tune and supporting mods.

Any idea what could be causing this? Could this be a clutch issue? Im just under 90k on factory clutch and flywheel.

Thanks guys!

Did you specifically ask them to inspect them and then talk with the person who actually inspected them or are you just assuming they're fine since the dealer didn't say anything about them? :icon08:

I've got over 100K on my stock motor and trans mounts and they're fine. Stock clutch is still going strong. FWIW...

Sounds more like a driveshaft issue to me...did it just start happening, or is this an ongoing concern?

No I did not specifically ask them too. When I picked up the car for other work the dealer gave me a sheet with a break down. I know some techs can be lazy and just say it’s good. However I have an extended warranty through a third party, so I would assume techs and asm is hold want to replace as much as they can. Transmission was replaced due to 6th gear synco grinding at about 60k. Tech said clutch had about 70% life left, but he’s been frustratingly wrong with my car before. I had a g35 before the g37 and had motor mounts fail and I know why to look for, or at least a good idea. The motor doesn’t move or knock and the sound I hear on the G37 is more of a thud, kinda feel it in your body a little bit.

I’ve considered that as well. The issue has been going on for a while, but is getting progressivly worse. Made me think maybe it was the clutch. The reason I’m now starting to look at it, I had planned on picking up a new car. Plans fell through, and now I’m keeping the G for the foreseeable future.


I really don’t drive the car hard. Haven’t raced it in almost 2 years. It’s really been a point a to b car for a while.

You're making a lot of assumptions...

And unless the tech dropped the transmission to physically check the clutch plate, there's absolutely no way he has any idea how much life is left. I doubt your 3rd party warranty company would authorize the labor for the transmission drop to check the clutch life.

My apologies, I’m at work and using my phone to post and reply. At 60k my transmission was replaced as well as my csc (had HDcsc installed). The tech said my clutch had 70% life left. This was at Sewell in Dallas TX.

The dealer that just did the multipoint inspection is in Phoenix, where I live now. I mentioned the 3rd party warranty thinking the dealer would want to find any issues they could to make money.

Anyway, any ideas what it could be? I’m about to just buy z1 motor mounts and transmission mounts and install them.

So it also shakes at speed while engine braking? It stops if you take it out of gear? Paired with the fact you've had the transmission replaced before, that's the most telling to me.

I'd start with mounts for sure. They could have even cross threaded them and left some slop while thinking it's torqued. Seen that.

How long ago was the work done? The labor should be warrantied for a while.

I think the work was done over a year ago. The dealership in Dallas is also the dealership that finger tightened The driveshaft to diff bolts, it is possible.

When in neutral I can rev the engineer without abnormal vibration.

All this being said, I usually work on my own car to avoid these situations, but if it’s something expensive that can be warranted, of course I go with the warranty. I left most of my tools in TX. I’ll start looking for a garage I can rent space in.


Let me see if I can get a video today on the way home from work!

Sorry for the delayed response, I was not able to get a video that showed the issue.

The main reason I think it is the clutch, some days the shaking is worse than other days.

Also the car will jolt back and forth is felt when starting from a dead stop, under normal driving.

When I got home I tried to shake the motor with my hands, and the motor is planted. When the mounts on my g35 failed you could shake the motor and hear a ping from metal hitting metal.

Hi guys, sorry for opening this old thread again.
I really would like to see any outcome here, did you find out what was the issue? Transmission or motor mounts did solve the issue?

I have similar issue - car shakes back and forth, mostly on accel/decel after cold starts, even the RPM gauge bounces up and down a little
Downshifts are as well pretty strange, after releasing clutch pedal car shakes, bumping back and forth a bit, even on fully operating temperature (everything, not only oil).

At 43k miles changed clutch and lightweight flywheel from JWT plus CSC and also urethane diff bushings.
Car still has the same behavior, with the above mentioned upgrades, no change in this bouncy powertrain response.
At the same time acceleration is delayed and preceded by some back and forth bounce/movement, hard to describe it :D

It doesn't look like he is active on this site anymore. :(

Jonesmeister1
Last Activity: 01-31-2019 12:40 PM

Uh, what a pitty :icon14:

My garage says it can be differential and that wouldn't be a cheap fix...

I think I can start with urethane motor and transmission mounts
I even put a gropro to underbody to shoot the transmission movement cause didn't see such a video anywhere, hoping to upload to youtube soon.
Anyway, there is movement but nothing exceptional.

On the other hand, 2010 with 47.5k miles on clock, it shouldn't be worn out diff, engine and transmission mounts might be aged already, garage checked transmission mount and said is not bad, still holds transmission, they had much worse cases on 370z.

UPDATE and bump of the thread :ugh2:

Just replaced the engine and transmission mounts to polyurethane ones and the shaking is even more noticable, due to stiffness of the transmission mount, I've got it properly recorded finally!
Now RPMs on engine braking are even bouncing up and down, not just dropping with pauses.
In this RPM range it's mostly noticeable.
videos: