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240SX IRS Swap


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#1 Ed260Z

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Posted 16 December 2005 - 11:44 AM

I've been doing a lot a research on what to do with my S30 lately, and I came across a very interesting swap. The reason for my search is that I plan on installing a RB26DETT into my Z, and I'm going to need a much stronger rear to handle the power. The easiest mod would be to get a Long Nose R200, and the accompanying adapters to make it work, 280Z companion flange, ect.....

There has been some debate on why anyone would ever want to do this. So this is what I've gathered up so far. (This not intended to be a how to in any way. I just saw a lot of scattered info, and I wanted a place to put it all. Hopefully the guys have done this already will chime in, and add to the post.) Because I still have a lot of questions!

Why do this swap?

You can get a vastly superior rear suspension set-up with a ton of current A/M support. It also allows the easier installation of the newer short nose R200 diff, with stronger half shafts, 5 lug hub and bigger rear disk brakes. And it will be cheaper to do (If I where handy with a welder) than the more common diff swaps.

If you do the math on what you would need to spend on the S30 IRS to get it to the point of what you get out of the S13/S14 IRS you will see a big difference.

No, you say well lets see:

R200 LSD I've seen as high as $800 (used not new or re-man)
280ZX Half Shafts $350 Rebuilt
CV Adapter $225
280Z Companion Flange $150
280Z Stub Axle $700
Adj Control Arms $600
Big rear brakes $900-1200

Plus a few other things. So we are looking at about $4000 to get a nice rear set-up.

Compare that to the 240SX IRS:

S13/S14 IRS $500
Q45 R200 $300
Q45 Hub & brakes $450 (w/new rotors)
Custom Half Shafts $600
Welding skill $0 to the moon

OK, so this set-up will run about $2000. That's leaves mw with $2000 more that I can dump into my motor.(Which is the whole reason I'm doing this to begin with)

Here is a great post by maichor on his swap. http://forums.hybrid...ead.php?t=96050

This is what I've pieced toghether so far on how to do this swap;

S13/S14 Sub frame modified by cutting off the front mount, and using the 3/4" hole just behind as the new mounting point for the front.

Weld a peice of flat stock on floor just in front of the "tool box", to support the front mount.

Welding in a new piece of 3X3 box tubing just behind the stock frame on the S30 where the Mustache Bar mounts. This will be the new mounting point for the rear.

Cut some sections of the stock rear sub frame for clearance.

Replace the 240sx hubs with the Q45's

Replace the 240SX Diff with the Q45's

Take some measurements, And have some Half Shafts made.

This is a very simplified run down of what you need to do, but as I said I still have a lot of questions on exactly what needs to be done.

The problem that I see wuth useing the S14 is that it's 5" wider than the S30, and requires some big flares in the rear.
The S13 is about 3" wider, so mild ZG flares will take care of that.

Here is a shot of Montoya's S13 IRS.

Posted Image


I'm not sure what the real benefit of useing the S14 over the S13 is? I hope that someone chimes in to answer that for me.

Please make any corrections to the info that I have, and to add more detail to it.


Just a few questions to start with;

1)What insulators are you using to mount the new Sub frame to the Chassis?

2)Will I have drive shaft problems since the Diff will be mounted in the center, instead of offset by 3/4"?

3)Can I bolt on the S30 Shock "Hat" to mount the 240SX Strut to the stock location on the Chassis?

4)Why use the S14 over the S13 sub-frame?

5)Do you need a spacer in between the rear mount and the frame?

#2 Drax240z

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Posted 16 December 2005 - 11:59 AM

A couple of guys on this site have done it, I believe Maichor is the name of the member that documented the whole thing... lots of pictures, etc.
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#3 Ed260Z

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Posted 16 December 2005 - 12:31 PM

Yehh, I was looking through a few of his threads. He did a real nice job on it. His thread seems to be the only one I could find that went into anykind of detail. Of few others have some info.
I was hopeing that we couild get enough input, from members that have done this, so that this could become a real information stop. And hopefully help people like me do a safe swap.

#4 Pop N Wood

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Posted 16 December 2005 - 03:15 PM

Several people have talked about doing this. I believe 2 or 3 are currently pursuing it.

Do a search. There is even a current thread that talks about an S13 vs. S14 swap. Do a search.

IMO it seems like an incredible amount of work for a questionanble gain. I am not sure why people are so infatuated with this particular swap.

You layed out your reasons pretty clearly. But a short nose diff has been done in an S30 numerous times. So the same drive train stuff you use with the 240 swap should work without taking the whole subframe. There are numerous rear disk conversion available for the S30 at considerably less than what you list price wise. But then I notice all of your prices on the 280 stuff are on the high side. And it seems pretty unfair to compare the price of a 280 set up with adjustable control arms to a fixed geometry 240 rear.

What I would really like to see is some qualitative assesment of the benefits of this swap from someone who is actually running it. Does the SX rear improve or hurt the handling/performance aspects of the S30? Does it change the balance of the car when the new rear is combined with the old front?

Maybe a hard assesment to judge fairly. But in my mind that would tell me whether all the work is worth it or not.

#5 tube80z

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Posted 16 December 2005 - 03:53 PM

Maybe a hard assesment to judge fairly. But in my mind that would tell me whether all the work is worth it or not.


I guess there are a couple of things that could be done. An assesment of the geometry between the two (RC, migrations, track changes, etc.) and perhaps what is the difference in weight. If you had a good guess for the CG you could come up with an idea if this would be better or worse and which way to tune.

Total hersay but I'm told that the stock setup has a lot of anti-dive built in. So if you don't address that you may find that you know have more power steer effects than a stock Z suspension.

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#6 JMortensen

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Posted 16 December 2005 - 03:59 PM

R200 LSD I've seen as high as $800 (used not new or re-man)
280ZX Half Shafts $350 Rebuilt
CV Adapter $225
280Z Companion Flange $150
280Z Stub Axle $700
Adj Control Arms $600
Big rear brakes $900-1200


Just a counter point here. I was able to do this for quite a bit less money.
R200 LSD $325 used
I put a new pinion bearing in and shimmed the LSD at a cost of $75
4.11 gears $150 (works for me, probably not for you, if you could keep the 3.70s then subtract $150
300ZX CV adapter $215
300ZXT CV shafts $135 (disassembled and greased up for $10 in grease)
280 stubs and companion flanges $150
Adjustable control arms - made my own toe adjuster instead $15
JSK brakes - ~$500 for the rear when completed, no longer available...

So there is a whole done up rear for less than $1600. A NEW clutch LSD is ~500. Even if you bought an open R200 and retrofitted the LSD you should still be in the $2000 range completed.

A lot of what you listed there simply isn't necessary to complete the swap, and some of it would still need to be done with the SX rear suspension if you were to build it to a similar level, like adj. control arms and big brakes.
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#7 rudypoochris

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Posted 16 December 2005 - 04:59 PM

This might be a newb question do the stub axles really cost $700?

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#8 JMortensen

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Posted 16 December 2005 - 05:38 PM

The billet ones from MM do. Then tack on $395 for the billet CV adapter...
http://www.modern-mo...&products_id=62
http://www.modern-mo...&products_id=63
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#9 260DET

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Posted 16 December 2005 - 06:51 PM

A bare S13 cradle weighs ~28kg so that is being added, plus the extra weight of the partial subframe which has to be built in to the S30 body for the cradle to bolt to.

A fueled up stock S30 with driver tends to be arse heavy as it is, so the above is being added plus the extra weight of the S13/14 suspension and drive components over their S30 equivalents.

If extra is being added up front to help balance the weight distribution thats a help. But often these sorts of mods are coupled with lighter and more powerful engine swaps.

Anyone who does this sort of modding may want to consider testing out the handling of such a modded S30 away from other traffic. Particularly to see how the rear end grips in corners. Which can be fun anyway :)

EDIT- S12 changed to S13 in the first para.

#10 Ed260Z

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Posted 16 December 2005 - 08:27 PM


.................There are numerous rear disk conversion available for the S30 at considerably less than what you list price wise. But then I notice all of your prices on the 280 stuff are on the high side. And it seems pretty unfair to compare the price of a 280 set up with adjustable control arms to a fixed geometry 240 rear.

Maybe a hard assesment to judge fairly. But in my mind that would tell me whether all the work is worth it or not.


I seem to have taken some heat here for how I priced out the 280 stuff. Most of the prices are from Modern Motorsports. I did a 280ZX rear disk conversion for $500, but that's a 10" disc. If I'm not mistaken the Q45 has a 12" rear disk. Modern Motorsports has a "Big" 13" rear disk set up for $1225. And I thought that the S13/S14 had toe adjustment.

I used Modern Modersports because they are a very good company, and there stuff is purpose built.

And yes I hope that the members have done this will chime in with there assesment.

#11 Hypertek

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Posted 16 December 2005 - 08:53 PM

The price list you got i think can be done wayyy cheaper.. I bought a replacement subframe for my s13 for 80 bucks at a local shop, but it was bare since i bent mine from drifting.. But usually you could probably find one around 200 or so if you check 240sx forums. I picked up a full z32 rear end (mainly suspension arms and the whole brakes) for $100, but that was just luck and i slapped the brakes into my 240sx.

Advantage over subframes?? None- mainly just different mounting locations, as s14 is spread further outward if I recall.. J30 subframe will work as well. Id stay away from using a HICAS model s13 rear subframe, I dont think You would be able to make that work (nor would u want it, it wieghts more as well). S15 silvia subframe has its advantages over both, I forget why, but S14 suspension arms are compatible with it and its mounting points are simular to the s13.

Running 240sx rear coilovers will have tons of adjustibility, but your going to have to match them up in the front with something exceptionally stiff. 240sx coilovers are probably going to feel alot stiffer on a Z.

#12 Ed260Z

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Posted 16 December 2005 - 09:08 PM

Can you use the S14 sub frame with the S13 arms?

The S13 uses 4 bolts to attach the diff, and the S14 uses 2. Most of the LSD's I've seen have 2 bolts, and I don't want to lose the finned cover off of these difs.

#13 Hypertek

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Posted 16 December 2005 - 09:28 PM

i dont see why not.. however, the rear upper control arms are shaped different between s13 and s14, they are different to allow room for the strut, so I presume the location is slightly different.. But s14 rear upper control arms will work on s13 since it clears (im sure that sounds confusing)

http://us.st11.yimg....ts_1877_1194085
This is BattleVersions rear upper control arm, they make 1 type of arm that fits both s13 and s14.

#14 Ed260Z

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Posted 16 December 2005 - 09:38 PM

You just have to love the A/M support that's available. Another big reason why I'm considering this swap.

There has also been some question as to weight gain. Although I havn't weighed these items, I can't imagine there being a big gain in weight (if any). And my uderstanding that most engine swaps bias the weight forward 100-200 Lbs (except 4 bangers like the SR20). But even that has no real effect on the car.

#15 JMortensen

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Posted 16 December 2005 - 09:44 PM

RB will bias it forward, V8 biases back. It does have a real effect on the car. See all those custom adjustable links in that picture? There's your adjustable control arm equivalent.
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#16 rp975

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Posted 16 December 2005 - 10:26 PM

Hi all,

The question that I would like to know is what are you guys going to do about the forward link in the above photo,as where the inner mounting or pivot piont for this arm is, it doesn't clear the standard s30 unibody?

I have seen an r32 rear sub frame put into an s30 and that person moved this mounting point down to next to the lower control arm mounting point, but this changes how the wheel acts, as it moves up it aslo moves inward which doesn't seem like a good idea to me.

What have you guys done , or what do you think about this?

#17 Ed260Z

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Posted 17 December 2005 - 06:48 AM

If you look at maichor's pics. it looks like he cut out the "tool box". May be you could notch the interference point, or try and slide it back further in the chassis.

#18 Ed260Z

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Posted 17 December 2005 - 07:32 AM

This is in response to a post that was apparently removed by the Moderator. It was a bit of a flame on the whole concept of this swap. But this is a forum where we discuss ideas of hybriding the Z. (Hence the name). In the post he said that the S13/S14 IRS was not any better than the S30 IRS. In all of the posts I've read people remark about how well the 240SX handles, I would assume that has something to do with the suspension. (But I could be wrong.)
I had a new S14 for a few months, when I worked for Nissan, as a demo and I thought it handled very well. The only problem was the lack of power from the engine.

There was also some question as to the validity of this swap for a stonger diff. I never said that Long nose R200 could not take the power. (The R180 could probably handle it) The reason for this swap IMO is to kill several birds with one stone. Like Diff, Brakes & Suspension.

#19 TimZ

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Posted 17 December 2005 - 09:16 AM

In the post he said that the S13/S14 IRS was not any better than the S30 IRS. In all of the posts I've read people remark about how well the 240SX handles, I would assume that has something to do with the suspension. (But I could be wrong.)
I had a new S14 for a few months, when I worked for Nissan, as a demo and I thought it handled very well. The only problem was the lack of power from the engine.


I think that this is the thing that worries me about such mods. I don't think anybody is saying that there is anything wrong with the 240sx suspension. It works great, as Nissan spent alot of time engineering it into the 240sx. The worrisome part is that nobody seems to know exactly how this relates to it's installation into an S30. There are numerous suspension geometry issues that could really cause problems in such a swap, and I'm getting the feeling that most people don't even know what questions to ask, let alone know how to solve them.

I think that it would definitely be possible to make this swap work really well, but if the approach is to just weld in an S13 subframe so that all the parts fit, nothing binds and the car doesn't dog-track (a huge task in and of itself), I think you'll be lucky to just end up with something that just works _as well as_ the stock setup. More likely, you'll end up with something that is noticeably worse, and it won't be easy to fix it.

And if you start moving link mounting points around around to make things fit, then God help you... :shock:

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#20 Ed260Z

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Posted 17 December 2005 - 11:40 AM

The worrisome part is that nobody seems to know exactly how this relates to it's installation into an S30. There are numerous suspension geometry issues that could really cause problems in such a swap, and I'm getting the feeling that most people don't even know what questions to ask, let alone know how to solve them.


I would love to hear some input from the guys who have done this already. With the big question being; Was it worth it?




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