i have very rusty crossmembers on my 09 g37s and they needed to be replaced. I went to the junkyard and found the replacements for both front and rear at very decent prices. my only issue now is, i don't know what bolts are used in the process of replacing the crossmembers.

 

Start by jacking off the car (lmao I heard Scotty Kilmer say that in one of his videos, couldn't help it). If it is the front crossmember, lift the front end. If it is the rear, lift both ends. Then, locate the crossmember and just try to find all the bolts that you can see that are keeping it up. Have a breaker bar and cheater pipe handy in case the bolts are super tight and you don't have an impact wrench. Once you have an idea of what kind of bolts and how many there are, remove them one by one until the thing falls on ya. Jokes aside, I would have someone assist you while removing it, or you can lift your jack up against the crossmember, remove the bolts, then lower the jack slowly so the damn thing doesn't crush you.

Things to keep in mind when removing any crossmember (front or rear):
- Front and rear crossmembers will require you to remove various suspension parts
- Rear crossmember will require you to remove the exhaust, heat shields, driveshaft, half shafts, and differential,

Long story short, if it is the front then you should have no problem dropping it. If it is the rear, start a Go Fund Me right now and save up those dollars to have a shop do it for you (unless you are comfortable doing it yourself, then all the power to you). If it is both and you aren't capable of doing it all yourself, sell the car and get something that doesn't have rusty crossmembers.

I just re-read your post and it looks like you are asking what type of bolts you need. If that is the case, then that is a stupid question to ask (no offense) because if you plan on removing the crossmembers yourself, you will have all the bolts you need after removing them.

 

Your standard metric set will do.
10,12,13,14,17,19,21,22mm will get it out. (sockets and long wrenches)

Jack and stands are a must.

As previously stated this is labor intensive especially depending on the condition of yours. If you plan on tackling this yourself make sure you have an extra set of hands, rust penetrant, patience.
Good luck!

 

I had mine replaced not too long ago as it was rusty as well. The front crossmeber for me was: 544B2-EG300. I needed 8X of these bolts: 11298-EG30A. I would go on a site like Infinitipartsdeal and type in your VIN so you get accurate part numbers. For the rear stay bar you need 2X nuts and 2X bolts. The 2X nuts for me was: 55269-2Y00A (they don't list this on any part diagram). The 2x bolts where: 74397-4U00A. There is also a center bolt that threads into the rear stay bar that secures the rear diffuser, which is: 08146-6122H, I believe 3X are used total to secure the diffuser.

 

can anyone confirm that the front crossmember is not swappable between AWD and RWD? doesn't look to be the same but one site said the RWD would fit, got me second guessing. My front is rusted pretty bad, no luck at junkyards in my area.

 

Though ANY crossmember will fit any trim you need to stick with the driveline you have. So an AWD member wont work on a RWD and vice versa. AWD members can ditch the system by swapping members and AWD components.

 

I have also heard that Q60 cross members will fit the G37s (with little trimming). Supposedly, there are 2 tabs that need to be ground off first, but other than that, it is plug and play. Plus, they beefed up the cross members on the Q's

 

Just wanted to add, that with a good penetrating oil (PB blaster) and a long breaker bar, no bolt is impossible to remove (knock on wood).