350Z LSD in R34

[DieselTime]

350Z LSD in R34

Hey all,

Fair warning, this might be an incredibly dumb question as I'm only just getting into the whole car modification scene and don't know much about how everything works, but I'm looking to get an LSD for my 25GT. Unfortunately the amount of info on this topic isn't so much scarce as just contradictory, some people say a GTT's will fit, others anything from the 33 side of things, an S15's might etc. I recently came across a 350Z LSD (I wanna say R200) and accompanying axles, my question is this: could I feasibly swap all this into my R34? I've heard the 350 has considerably stronger axles due to a ball and cage design so I guess that's a bonus, but I assume the bolt patterns on my current axles won't mate to the 350's LSD housing, hence the need to swap those out as well.

Any thoughts on this'd be greatly appreciated.

[GTSBoy]

I actually don't know the details on the 350Z's diff & shafts, but it would close on 100% that they are a 5 bolt flange, like the R32/3/4 Turbo diffs, or the 6 bolt like the R32/3/4 GTR diffs.  What they will NOT be is the same 3x2 bolt flange that your N/A diff will be.  So, if you are to swap the diff into the R34, then you will definitely need the driveshafts too.

But this is where it starts to get complicated.  Just because it is an R200 does not mean that it will all go together.  The housings could be different.  Mounts in different places, etc.  The internals may be swappable, but then there are variations in how long the input shaft section is, depending on where the speed sensor for the original car is etc etc etc.

All in all, the smart thing to do is to buy an LSD centre to suit your diff.  This is not a difficult thing.  It will cost you upwards of a grand for a new Nismo centre with matching stubs, or similar but possibly smaller money for a Cusco or Kaaz, or any of the several other aftermarket options....none of which are as good as the Nismo centres.  And that grand will be the best way to go about it, because messing with Nissan diffs can drive you crazy.  You start out thinking you're going to get away with it cheap and you end up spending more than you thought possible.

[DieselTime]

Jesus, it's never easy is it? I did take a look at the Nismo centres but they're unbelievably expensive for what they are and I was worried I might run into some issues what with a lot of them being manual only and my car being an auto. I've heard an S15 setup will fit and, correct me if I'm wrong here, they have the same bolt pattern being a 3x2, but in this instance the GT had the turbo model subframe installed so I dunno how much difference that would make to the installation process.

[GTSBoy]

Subframe no difference.  S15 vs R34, the thing to be careful of is the possible (likely) difference between the length of the front of the housing.  The S15 had a speed sensor on there that the R34 doesn't.  I'm pretty sure it makes the housing longer.

The S15 helical diff is the same helical centre as the R34 helical (which are as rare as hen's teeth).  The problem is, you wouldn't put an S15 diff directly into the R34 anyway, because the S15 ratio is like 3.7:1, and the R34s should be 4.11:1.  So if you're to use the S15 helical centre, you have to pull both diffs apart and swap the centre onto the R34 gears anyway. Once you've done that, you may as well have just bought a Nismo centre anyway.

FWIW, I have an S15 helical centre, using R34 gears, in an R32 housing, with S14 driveshafts, in my R32.  It was a a LOT of f**king about.  I wouldn't recommend it compared to the more sensible alternatives.

[DieselTime]

Yeah, definitely sounds like I'd be building up to a headache, Nismo GT centre sounds like my best option.

Just in the interest of exploring all my options, one guy on here claims the R33 GTST diffs are a direct swap (although there was some confusion due to his axles being 5x1 rather than 3x2, possibly due to his car being a GT4 rather than a standard 25GT). Given this, would it be worthwhile exploring the possibility of an R33 GTR mechanical diff? Presumably I'd need the accompanying axles as it'd be a 6x1 pattern, or am I just going to run into the same problems as the S15?

Cheers for all your info so far mate, seems every time I have a question you're the go-to guy.

[GTSBoy]

GTR diff requires GTR uprights at the outer end of the (6x1) driveshafts, because the hubs/splines are different.

Are you doing this to turbo/boost the thing or is it staying NA?  You'll never tax the strength of the tripod CVs in the 3x2 bolt axles if you're staying NA, so keep it simple if you can.  If you're converting to turbo, consider the standard advice on this forum to sell it to a P plater and buy a GTT.

[GTSBoy]

And following up the direct swappability of R33 GTST diff......yes, it will go in.  You cannot swap the stub axles from the open NA diff into the viscous GTST diff, though, because they are different.  So if you use a GTST diff, you need the 5-bolt shafts to go with it.  Not a huge problem.  Except that what you have bought and put in is a diff that is a worthless piece of shit.  If the GTST diff has some sort of aftermarket mech centre in it, then that's a whole 'nother matter.  But the viscous diff is only deserving of being used to earn $0.30 at the scrap metal merchant.

The other obstacle you may find with complete diff swaps is the type of ABS sensors on the housing.  R33 GTST and R34GTT should have the same type, but others will be different.

 

[DieselTime]

If I can afford it in the next few years I'm actually hoping to LS swap it but we'll see how it all goes, chances are I'll end up buying a GTT in the end but for now I'm going to swap out parts so I guess if I can improve things like axles I may as well, at least for the next dumb kid to pick it up haha.

So GTST diffs are a no-go, could you explain what you mean by uprights?

[GTSBoy]

The rear suspension knuckles.  The upright that locates the hubs.

Edited July 10, 2017 by GTSBoy

[DieselTime]

And so by using those would things like my control/camber arms still bolt up without issue? Hopefully not as dumb a question as I assume it is.

[GTSBoy]

They should.  Does an NA R34 have HICAS?  If not, you'll have to do some small extra stuff to change from HICAS tie rod ends to the bushes that go through the same holes on the [steering] arms of the knuckle.

[DieselTime]

I don't think the NA models came with HICAS, no. What would be required to change the bushings, is it a simple swap-out job, take out the tie rod ends and replace them with bushes from my current knuckle or is it a little more complex than that?

I take it using a HICAS lock bar wouldn't work as there'd be nothing on the GT side of things for it to hook up to?

Edited July 10, 2017 by DieselTime

[GTSBoy]

You're already far ahead of the pace by not having any HICAS stuff on the car, so no, lock bars, etc are not required.  The GTR upright will have a taper inserted into the hole in the steering arm so that it works with the balljoint on the end of the HICAS tie rod.  The non-HICAS upright will just have a plain hole, to take a bolt and bush arrangement, because the toe control arm on non-HICAS cars is just another suspension arm.

The taper needs to be driven out of the GTR steering arm.  Not always simple.  But at least if it is off the car already (as it will be!), it makes it easier to do.

Edited July 10, 2017 by GTSBoy

[DieselTime]

So is it simply a matter of removing the taper, replacing it with the bushings from my current upright and then hooking it up to my non-HICAS toe arm, or am I misunderstanding something?

[GTSBoy]

It should be.  It would be on an R32.  I've not fiddled with 33/4 rear ends to be 101%.

Although....there's probably 1 more trap.  The rear lower shock mounts are different between various cars and GTRs.  Some of the R34s are the same as GTR (and different to R33 GTST).  So.......there could be a need to change rear dampers.

All in all, I wouldn't pursue a GTR diff transplant without completing that research!

[DieselTime]

Yeah, sounds a bit too tricky for me to sink over a grand into it based on guesswork.

While we've got a bit of a ball rolling, were I to put a Nismo GT setup into my current casing, could I use one designed for a GTT so I could utilize the 5x1 pattern hubs over the dodgy 3x2s? My understanding is there's several variations with the GT, GTT and GTR all having different setups

[GTSBoy]

Yes, if you can find a set of stubs you'll be right.  The easiest thing to do would be to go buy a viscous LSD from a 34 GTT.  Get the Nismo centre to suit that.  Get it put together and then throw the whole lot into the car with 5 bolt shafts.  Much less stuffing around.

But, the only way you will test the strength of the "weaker" 3x2 CVs is if you do actually do an LS swap.  They're the same joints/shafts used on Silvias and they happily take a lot of power in that application.

[DieselTime]

So I take it the cases between the 25GT and GTT are different then? I can't simply buy a Nismo GT LSD for the GTT and throw it in my current case? Were I to buy the full GTT LSD setup, would all I need be:

-GTT stock LSD

-Nismo GT internals

-GTT 5 stud axles

and these'll all bolt up to my car without much drama in comparison to the R33 GTR gear?

Appreciate the info man, seriously, been a big help. Realize I've been asking a lot of questions but hey, gotta learn somehow right?

[Duncan]

well you can almost certainly buy a nismo diff centre to suit it (whether or not that is GTT I'm not sure, but the catalogues will say). Same goes for  Kaaz, Cusco, whoever else if you want a similar outcome cheaper.  Putting a matching centre in your current diff will almost certainly be cheapest because you only need to deal with the #splines on the output shaft. You even keep your current ratio because the one in your current diff is re-used.

So just call a seller who knows their catalogue and order the right part#

I'd have to say though, this is a fair whack of money for something that isn't really going to make much difference, unless you are embarrassed by single spinner burnouts or something.  If you genuinely want your car to drive better, swaybars or better tyres, or maybe even better brakes would be the place to start rather than the LSD.

[Leroy Peterson]

I can't shed too much light on skyline specifics... but I did go to some effort with my Y34 (same rear end as Z33/V35 for the most part). Sourced an R34 GTT helical diff, and even just looking at the centre while they were still in the housings, you could tell it wasn't going to work. I got told it would work if you swap over the half shafts etc, but it needed some serious shims at a minimum.

I ended up getting an NM35 helical diff centre and took it to the diff workshop. Even though it was "bolt-in" one of the half-shafts needed to be machined down to work. $150 for the diff centre, $550 labour. So it worked out well for me, but I was lucky to sell the R34 diff at the same price I bought it... not to mention the time it took me to gather all the bits, disassemble, compare etc.

Lesson learnt: it is easier to just buy an aftermarket swappable centre, even if its pricey UNLESS you are 100% sure of a direct swap (and by 100%, I really mean 100%).

Upgrading diffs was one of the best mods I did. Car drives so much better. Next to no wheelspin, ever.