Differential stud/bolts upgrade questions
 

I snapped the rear stud on my Z1 rear differential cover and am upgrading to the Greddy unit as it has 2 rear studs. I have a fabrication shop adding in a second rear mounting hole into a 2008 subframe for a second WhiteLine bushing. I am looking to upgrade the rear studs and the front differential bolts to Grade 12 hardware on top of this.

1. The stock rear diff stud is 58mm long and the threading into the diff cover is M14x2.0. I have found a Grade 12 M14x2.0 bolt (here) that is 58.8mm long overall, 50mm length with 8.8mm hex head. I assume the stock nut is approx. 8mm. Can I use this bolt as a rear diff stud replacement? If not, any suggested alternative?

2. I can find OEM replacements for the front differential bolts however I can't seem to locate length or thread information about the bolts. I have the replacement part # as 55424-AG00A. Does anyone here know the length and thread information about this item?

I have searched extensively (which is how I got the idea of the second mounting stud instead of one of the diff cover brace options available). I apologize in advance if this has been asked elsewhere and appreciate any input. Thank you.

The front diff bolts....Shank length is 55mm of ~11.90mm dia, including a slight 2.75mm long taper to the threaded M12x1.5 portions ~11.79mm diameter, which is~35mm long. Total length under head is ~90mm exluding a roughly ~5mm conical tip which I assume can be omitted.

Why would you do all this to run an inferior diff bushing?


https://cimg0.ibsrv.net/gimg/my350z....b67248bff7.jpg

Oh and its a 17mm head 23mm flange width.

Guitman32,

Thank you for the information. I think finding an "off the shelf" grade 12 replacement for the front bolts may be more time consuming than intended, if there is even an available option. Do you think the grade 12 bolt I found would work for the rear bushings? Anything you think might be a sticking point in using it?

There are 3 main reasons I am going to run the Whiteline bushings.
First was cost, I had already purchased the entire whiteline bushing line up, so going to two solid rear diff bushings would be costly beyond the sunk cost of already having 1 of the bushings (whiteline offered me a good deal for the second bushing) plus when snapping the rear stud I roughed up the Z1 housing pretty bad so I already needed to buy a new cover and figured why not try doing the double stud setup like the Nismo 380RS (the second mounting hole for the Diff Braces is already holding 2 Bosch 044 pumps so with all the work necessary already, I figured why not take a different approach?).
2nd, this was and is going to be my daily driver (with a backup car of course).
3rd, locale. Miami roads near me (and in general) are terrible and I was hoping to have a somewhat comfortable ride quality while also being able to put down the power my car is making (660). You bring up a good point however, I was really on the fence and considered going solid.

Yes its a weird size and there is even a small taper on the bolt from the shank to the threads. I dont think the bolts are the issue. The use of compliant bushings is what is causing your setup to snap. Esp with that much power you should consider solid diff bushings and at least the SPL subframe inserts.

Though I definitely appreciate wanting to maintain the streetability...with solid subframe and diff bushings the increase in NVH is significant.

Have you seen the SPL urethane diff bushings? They seem neat in that they have a compression fit, which is what you want if you are going to run urethane. The project definitely sounds cool though.

I have not seen the SPL urethane diff bushings, I checked their website and only saw the Pro Solid line. I'll call them later to see if they are available. Are the whiteline bushings not compression fit?

Have you heard any comparisons between the subframe inserts and the whiteline subframe bushings? I thought about the inserts but when I purchased the entire whiteline line-up, those were not available. I did the whiteline purchase 2 years ago, got every bushing they offered and now finally have the downtime (the only positive of snapping that stud) to get them installed for the subframe, differential, and suspension components. I'm going to take extensive pictures of the second mounting stud project and share for anyone else interested.

Sorry I meant Z1 urethane bushings...

https://www.z1motorsports.com/z1-pro...s-p-10356.html

https://cimg7.ibsrv.net/gimg/my350z....4f1cd5eca9.jpg
https://cimg8.ibsrv.net/gimg/my350z....4296543b2e.jpg

Haven't driven the car yet but the rear end modifications have been complete. Attached pictures for anyone who might be interested in completing this modification in the future as the original post on this forum where I got this idea does not include pictures.

Looks like that shop did a really nice job with the fabrication, too bad nissan didn't set it up like that from the factory.

Looks good man! Let us know how it holds up w that power.

@guitman32 I have driven the car now for about 3 months and it holds the power great. No melting issues yet even when doing multiple 160+ highway pulls in the FL heat. I highly recommend this setup.

@mrf350z Sorry, I just noticed these comments. I will get under the car when the weather is better (hopefully this weekend) and measure for you.

Thanks! I accidentally tapped my subframe to M12x1.5 bc this is the only information about the size of these bolts online. THEY ARE ***M12x1.25*** AND NOW MY SUBFRAME HOLES ARE STRIPPED SO I’M HAVING TO DRILL IT OUT TO FIT M14x1.5 BOLTS!! I just had to login to post this so that hopefully others will not also make the same mistake!!! The other values are close enough.

Just bought this diff cover second hand and was wondering if it came with a baffle plate that needed to be attached on the inside because mine just came with the diff cover and the fittings please lmk thanks