Hi guys. I've been lurking this forum since early this year when I started researching the G35, and then bought my 2008 G35X back in April. I thought I'd share this odd solution to a vibration problem my car had, because I didn't see any reference to this potential issue here other than this thread where the problem was not identified: https://g35driver.com/forums/v36-eng...erating-3.html

the TL;DR answer first: the 2008 G35 uses different engine mounts than some 2007 and previous years, and using the older mounts lets the engine sit too low and causes driveline vibrations on acceleration. The 2008 G35 engine mount is the same as used in the 2009 G37.

The full story:
I bought the car in early April with 130K miles; I met the seller in town and test drove the car for about 30 minutes and didn't find any issues, it ran and drove great. The next day driving to work I discovered a loud vibration/groaning noise when turning hard left and accelerating, and have been trying to solve that issue up until yesterday. The noise seemed to diminish and even go away as the driveline warmed up, especially after sitting or driving around town at low speed, but it also got progressively worse to the point that the vibration happened when going straight or turning.
Various things I suspected were: transfer case clutch noise & bad electric actuator, transmission mount, driveshaft center bearing, U-joints, CV joints, wheel bearings, and even the transmission. I replaced a number of these along the way, and even replaced the transfer case which didn't fix it. An interesting point was that the noise was very loud inside the car, but wasn't audible outside. It could be felt in the feet, seat, and steering wheel, and sounded like it came from the engine bay.

The other day I decided to replace the engine mounts since I was working in that area to replace the struts anyway. The engine mounts didn't show any tears or signs of hydraulic fluid leaks, but when I removed them, it became obvious they were different than the replacements. One of the key giveaways was a large thick random washer on top of each one as a spacer, obviously not a factory installed item, and the mounts were dated 8/2015 so they had been replaced. The old mounts were shorter than the replacements by about 1 inch or more, and used a single bent steel arm as a limiting strap instead of the sheet metal cage around the new mounts.

Now that the new mounts are installed, the engine sits higher in the engine bay, and it idles and drives silky smooth, far better than it ever had before. The vibration noise is completely gone. I think the engine or transmission must have been rubbing on something, but couldn't see what.

To be clear, the old mounts were not bad, they were just the wrong mount for that year, 2008 and newer only; they were listed as the correct mount for a 2007. I don't know, but suspect some 2007 sedans (maybe X models only?) may have used that newer mount as part of a rolling change during the model year. Just something to check if you experience driveline vibrations.

Hope that helps!

 

but thanks bud!

 

Yeah, wish I'd thought to take pics while I was doing the work. A side by side pic of the mounts and a couple pics showing the engine height difference would have been good, sorry.

Since I didn't take pics though, these links show the two different mounts, these are aftermarket Duralast parts but the appearance is the same.

This is the old mount: https://www.autozone.com/external-en...7_599907_12553

and this is the new taller mount: https://www.autozone.com/external-en...907_12553_1196

 

Thanks for sharing.

 

I have an '08 X and when looking up parts on Infiniti's site, multiple items will show two different part numbers based on the production date.

 

I suspect there were probably some rolling changes as Nissan/Infiniti integrated the 3.7 L motor into other models. Based on the part numbers I see on the Infiniti parts site, I think this happened during the 2007 model year for these engine mounts in the G35 Sedan.

On the Infiniti site, I see two mounts listed, but one part number is superseded by the other, and pictures I found online of both part numbers look the same as the newer mount I referenced above that I installed in my car, so I don't think that's the difference I'm talking about with the old vs new mounts. The Infiniti part numbers for my 2008 X are 11220-JK500, superseded to 11220-1BA0A. It looks like these two part numbers are just revisions of the same mount style.

For 2007, however, Infiniti does list the two different mounts as you said:
- 11220-JK00A (old mount) for production range 08/01/2007 to 08/01/2008
- 11220-JK500 superseded to 11220-1BA0A (new mount) for production range 08/01/2006 to 08/01/2008

That of course is not very helpful from Infiniti, since the production date listed for the old mount is inside the production date for the new mount. Seems if you have a 2007, your car could have used either mount but hard to know if that was based on a specific date or other details. I think it's pretty clear though if you have a 2008, only the newer mount is appropriate and the old mount is incorrect.

Also, it looks like the 2WD G35 sedan models for 2007-2008 all used the older mount style 11220-JK00A, so the newer taller mount is specific to the AWD models for those years.