This is really disappointing, I was almost set on the BC coil overs for my sedan. Is this an AWD only problem or do RWD cars experience this as well?

 

According to this article the front preload is 4mm, Step # 10 in this link
Infiniti G37 or Infinti G35 BC True Rear Coilover installation steps showing step by step instructions on installation, height adjustment and measurements

 

Is that nylon gasket the one shown in the vid I posted or is there a cushion / gasket
That sits between the top of the spring and coil mount? Maybe just a thicker gasket would work . I'm starting to think about calling and stopping the order ? do we have no options on coils other than these for the AWD's

 

The vid you posted is a true rear coilover rather than the separate spring/shock setup of the BC BR series for the X (I don't think they make true coilover style for the X). In this link see step #3 for the significant difference in the amount of cushion from OEM to the coilover mating surface, plus the rubber is softer in the OEM cone so better sound deadening. I still think if this isn't the primary reason for the noise issues it's a strong contributor
Infiniti G37 Coupe BC Coilover installation steps showing step by step instructions on installation, height adjustment and measurements I

I think adding one of these in between the upper spring and the point where it rests on the height adjusting collar may reduce a lot of the shock.
I wish I had some time to install mine but I bought them off Ebay w/out exact measurements so If I were to do this over I would have measured precisely and ordered the exact size from this link~
energysuspension.com | Shock Boots & Coil Spring Isolators

 

I will be getting the Megan Street series coilovers soon (few weeks), and I will do the rubber isolator thingy you mentioned on the right rear, well most likely both sides for equality.

 

I think they're sold in pairs (at least mine were) so couldn't hurt to do both, anything to add a bit more isolation from the cabin can't be a bad thing.

 

Thanx again Blwent, again because I don't have these yet or installed why hasn't (or has) someone tired to install the factory cushion this is something I will look at.

On the Energy suspensions do we know the diam of the isolators we would need for the BC's. I may buy these also?

 

The factory cone cushion doesn't have the proper space to allow the height adjusting collar to sit flat against the body
They may have the info of the specific upper spring inside diameter on their spec sheet or could give them a call.

 

So just got off he phone with BC, at least he said he know about he issue? The ID is 97mm(3.8189 inches) and the OD is 30mm(1.1811 inches).

 

The D2 racing coilovers I have are true coilover shock and spring combo, not seperate. I wasnt sure if they still make them for the X sedan but I found them by googling. Here is a link Infinifi 2009-2013 G37X (4Dr Sedan, AWD) D2 Racing RS Coilovers Dampers Kit (D-NI-10)|D2 Racing High Performance Race Suspension Systems. This might be an option for the OP if the BC ones arent what he wants. I have no problems so far.

 

D2 is another brand that makes coilovers for the G37X, that was my first Coil's I purchased then sold brand new a while back. I'm regretting that now because the noise the BC produce isn't cool.

 

That's good to know, how long have you had them?
Why did you sell the D2s?

Having the true coilover setup may be the ticket since you're not dealing w/ that separate rear spring isolation issue.

 

Had them for a little more than a year or about 10k miles. So far so good. These are my first coilovers so really have nothing to compare it to. But I like them, especially the reliability end of it.

 

Sold them because I was oblivious to the fact of the unknown concerning the Brand, D2. Like I said I wish I can do it all over again.

 

Are those measurements correct? How can the ID be more than the OD?

Those measurements also don't match any items B linked either