240z s13 Frankenstein drivetrain help.🤯

[s528093]

Hey zilvia,

I’m a newb when it comes to gear ratio and just don’t know what to get for my build. I have a beat up 73 240z shell with no frame. I’m building it from the ground up using s13 front and rear subframes. It’s driven by a rb26 with a cd009 trans. My problem is I need to swap out the old diff and axles, and find the optimal gear ratio that would work well with my cd009 and rb. I want the z to be an all rounder with decent mileage and drifting capabilities ��. What should I get? Fabrication doesn’t scare me.

[JDM240z]

The old long nose diff and axles won’t fit the s13 subframe. If you plan on using the s13 subframe that answers you question. That gives you all the suspension and diff options you would ever need. R200 diffs from lots of nissans will fit. It’s not easy to swap the subframe but also not impossible. It’s been done. As far as gearing, that all depends on the intended use of the Z. For Top speed go for taller gear ratio 4.08. Faster exelleration a shorter gear ratio 3.69

[derass]

The Z33 and V35 have a ~3.5 final drive ratio.

So you should probably start there. Like anything between a 3.5 and 4.1 Any shorter than that (like the stock 4.1 from S-chassis) will rev pretty high of the highway.

As far as gearing, that all depends on the intended use of the Z. For Top speed go for taller gear ratio 4.08. Faster exelleration [sic] a shorter gear ratio 3.69

You've got that backwards. Bigger number = shorter ratio = more acceleration.

[s528093]

derass, I was thinking about using the 350z/z33 diff because the person who sold me the trans also has the diff for cheap. Problem is, how would I go about mounting it. Are there adapters? Can I swap internals? What axles do I get that is compatible with the z33 diff and the s13 subframe?

[JDM240z]

You've got that backwards. Bigger number = shorter ratio = more acceleration.

Good correction, that’s what I had meant.

The Z33 diff should fit in an s14 subframe. I think a few companies make front diffbushings to make it work. But don’t limit yourself to that diff. An S15 diff with output shafts will fit in an s13 pumpkin. 3.9-3.6 options.

[s528093]

Yeah I found those bushings and they are only for s14 and s15 models
https://www.maverick-motorsports.com/products/350z-370z-conversion-bushings

Other threads are saying to use a q45 diff with 300zx TT axles.
https://forums.nicoclub.com/install-guide-q45-differential-swap-into-240sx-subframe-t267924.html

Problem is with this thread is that it is asking me to upgrade to 300zx TT 5 lug wheel hubs. I have a set of watanabe 4 lug rims. I don’t want to switch out ton5 lugs. Can i run a q45 diff with z32 axles without upgrading the wheel hubs? :confused:

[JDM240z]

Can i run a q45 diff with z32 axles without upgrading the wheel hubs? :confused:

Unfortunately no. Ultimately 5 lug is the way to go IMHO.

[JDM240z]

You may be able to find custom axles to match the output shafts of the Q45 diff and S13 hub. But it would be more expensive than the whole rear end swap most likely.

[s528093]

So just to be super clear to put a q45 in my s13 subframe I have to swap my wheel hubs to 300ZX TT 5 lugs and buy new rims. My Watanabes are 15x10 with 315s in the rear. They are super frickin wide already and I don’t want to put a wheal lug adapter on. other wise it gonna look like a c4 corvette lol. Are there any other options I have with the rear end that let me keep my vintage Watanabe's?

[JDM240z]

Yes your correct. The q45 diff needs the hub swap. If you must keep the wheels just swap in a j30 VLSD. 3.9 ratio and a bolt on for the s13 subframe. Just make sure it’s from a 95-96’ J30 as the axles are the same bolt pattern.

[s528093]

https://dallas.craigslist.org/dal/bop/d/lewisville-infinity-j30/6811654110.html

Ok, yeah I’ve been doing reasearch on the j30 and I’ll go down that rout for now. I found this 96 j30, and planning on buying whole car for 500 from the dude. And sell the rest for either scraps or to copart. I was just wondering, since the j30 bolts on straight to the s13 subframe, do you think it’s the same the other way round. Bolt the s13 diff to the infinity j30, and sell it as a full running car.

He posted on the 5 mile app saying it’s a 96, but I have to check his Vin/title

Should I even change the diff? I could weld the stock diff or shimm it. Opinions?

[derass]

I would just swap the ring and pinion in the S13 diff to the ratio you want. And not mess with the hubs.

[s528093]

I’m running 315s in the rear. I’ve head welded diffs and large tires break axles in turns or drifts. Plus tire wear is not economical, and daily driving a welded diff is gonna suck.
So, just to be super clear. To change the j30 VLSD I just have to swap the back plates and just bolt it straight it. I’m assuming that since everything is the same I can put the j30 back plate on my old s13 open diff r200 and put that in the infinity j30 that I am buying, so I can sell it and make my money back.

[JDM240z]

Like derass said you could swap the ring and pinion for a lower gear, but I would definitely have a shop do the work.

For all swap info check out http://www.ka24development.com/vlsd.html

The s13 diff won’t bolt into the J30 easily. The J30 diff is slightly longer than the s13 open diff. It has a speed sensor on the nose that makes it about 3/4”longer. It also has a different front bushing setup with longer bolts and washers. You need the bolts and washers for the swap as the factory s13 ones are to short.

[AutechKouki]

If you want a gear ratio that's right for the cd009 with a s13 subframe you have plenty of vlsd options without having to spend too much or fabricate anything.

1. There's the 96 and older Q45 rear differential with a 3.53 gear ratio you could run with 6 bolt 350z axles and keep factory s-chassis hubs.
2. 97-01 Q45 diff with a 3.69 gear ratio and run J30 axles and keep s-chassis hubs.
3. 92-94 J30 rear differential 3.96 rear gear ratio with matching J30 5 bolt axles, of which is a direct bolt in and has the speed sensor that'll work out best with your cd009.

Keep in mind that the half-shafts from the Q45 are interchangeable between the first and second generation, meaning if you wanted to run 350z axles on a 97-01 diff you would have to source the older half-shafts and they would drop right in. They have a higher spline count so this is only true for Q45 diffs from my experience.