Identifying a diff R34 GTT

[LjB123]

Hey guys. Was wondering what the best way to identify the type a diff is? Theres a couple of diffs being sold near me for a R34, and I imagine theyre Viscous just like mine, as the helical are rare from what people say. Whats the best way to identify what exactly they are? Ive attached a photo of one, the other is just a photo of the whole housing, could i look for certain castings or anything to identify it?

Unfortunately I don’t know a heap about the physical appearance of diffs and identifying the type visually 

[GTSBoy]

Looks like a stock VLSD.

If you look in the hole in the centre, you can see some side/spider gears. That is NOT what a helical looks like.

If you look in there even closer, you will see something else just below the visible gear tooth. That looks to me like the viscous cartridge.

That is a piece of shit suitable only for supplying housing, CW&P, and possibly stub axles, for an upgrade to an aftermarket LSD.

The 5 bolt stub axle flanges show that it is from a turbo. If it is from a manual it will be a 4.11. If it is from an auto it will be 4.083.

You cannot tell what is inside a diff without taking the cover off. Even if there were reliable markings on the outside....people can change what is on the inside.

Edited March 12, 2024 by GTSBoy

[LjB123]

7 minutes ago, GTSBoy said:

Looks like a stock VLSD.

If you look in the hole in the centre, you can see some side/spider gears. That is NOT what a helical looks like.

If you look in there even closer, you will see something else just below the visible gear tooth. That looks to me like the viscous cartridge.

That is a piece of shit suitable only for supplying housing, CW&P, and possibly stub axles, for an upgrade to an aftermarket LSD.

The 5 bolt stub axle flanges show that it is from a turbo. If it is from a manual it will be a 4.11. If it is from an auto it will be 4.083.

You cannot tell what is inside a diff without taking the cover off. Even if there were reliable markings on the outside....people can change what is on the inside.

Thanks for that. So would the best bet be to just go the Nismo GT Pro setup for a bit of an upgrade? Mainly street use, don’t think i will ever track day it. 
 

When doing some research i saw these Kaaz Helical LSD’s, would these be only a direct bolt in with an already helical diff setup? Or are the stub axles etc. all the same just the diff itself vary?

https://www.cartel-aus.com/product/kaaz-super-q-lsd-helical-1-5-way-rear-nissan-skyline-er34-25gt-turbo-rb25det-99-02/

[GTSBoy]

OK, so some important points need to be made here.

The KAAZ diff is not, in itself, a helical. It clearly is a clutch type mechanical LSD, the same as any other KAAZ LSD. So I am going to go ahead and assume that when the say "helical" they mean that it is meant to go into a diff that was a helical. The reason that this is necessary is that the various stock Nissan diffs have different length stub axles. The VLSDs have one long and one short axle inside. The helicals are either exact same length or ever so slightly different (so technically one long and one short, but only just). I really should have paid attention while mine was apart recently.

So you do not want that KAAZ diff. And really, I don't think I would ever want any KAAZ diff because in my experience they are all nasty to live with. Get the Nismo and set it up as a 1 way.

Or, if you have to have a helical, look into using the Quaife centre. You have to make sure that you have the right spline count on the stub axles, as well as various other compatibility traps, but apparently they can be used in a Skyline diff. I just haven't looked into it closely enough to know the whole story because I already have a helical centre in my diff and spending ~$2000 to change to another helical is not on my immediate priority list!

Edited March 12, 2024 by GTSBoy

[LjB123]

27 minutes ago, GTSBoy said:

OK, so some important points need to be made here.

The KAAZ diff is not, in itself, a helical. It clearly is a clutch type mechanical LSD, the same as any other KAAZ LSD. So I am going to go ahead and assume that when the say "helical" they mean that it is meant to go into a diff that was a helical. The reason that this is necessary is that the various stock Nissan diffs have different length stub axles. The VLSDs have one long and one short axle inside. The helicals are either exact same length or ever so slightly different (so technically one long and one short, but only just). I really should have paid attention while mine was apart recently.

So you do not want that KAAZ diff. And really, I don't think I would ever want any KAAZ diff because in my experience they are all nasty to live with. Get the Nismo and set it up as a 1 way.

Or, if you have to have a helical, look into using the Quaife centre. You have to make sure that you have the right spline count on the stub axles, as well as various other compatibility traps, but apparently they can be used in a Skyline diff. I just haven't looked into it closely enough to know the whole story because I already have a helical centre in my diff and spending ~$2000 to change to another helical is not on my immediate priority list!

Yeah might just go down the Nismo route, easier to sort out and my skyline is just a weekender, so doesnt get heavy use. All i can find is the 1.5 way/2 way diff from them that can be changed between the two. Is there one that is 1 way?

[Murray_Calavera]

1 hour ago, LjB123 said:

Yeah might just go down the Nismo route, easier to sort out and my skyline is just a weekender, so doesnt get heavy use. All i can find is the 1.5 way/2 way diff from them that can be changed between the two. Is there one that is 1 way?

You'll find plenty of street cars with the nismo 1.5/2 way diff. I'm running one and I really like it. 

If you are 100% set on getting a 1 way diff, I think Cusco still offer them. 

[GTSBoy]

Somewhat intense guide to Cusco diffs

https://www.cusco.co.jp/en/pdf/LSD Guide Final.pdf

 

Sadly, I'd forgotten that there is no 1-way Nismo GT Pro option. Which is a shame, because various users here have said that even the 1.5-way can be a bit annoying in a streeter.

[LjB123]

10 hours ago, Murray_Calavera said:

You'll find plenty of street cars with the nismo 1.5/2 way diff. I'm running one and I really like it. 

If you are 100% set on getting a 1 way diff, I think Cusco still offer them. 

Im not particularly set on anything, dont know a heap on diffs for R34’s and the options, just what i could google and read about on forums like this. Just looking for the best option, as although my diff is ok for now, i would like to change it in the next few months or so as its still completely stock and getting on in age, would rather change it out sooner than have it clunk out later

[LjB123]

10 hours ago, GTSBoy said:

Somewhat intense guide to Cusco diffs

https://www.cusco.co.jp/en/pdf/LSD Guide Final.pdf

 

Sadly, I'd forgotten that there is no 1-way Nismo GT Pro option. Which is a shame, because various users here have said that even the 1.5-way can be a bit annoying in a streeter.

Yeah fair enough, that’s unfortunate there isnt a 1 way from Nismo as I imagine for majority of people modifying their Skyline it would be a popular choice

For me its a weekend street car, driven once a week or for a whole weekend every so often, don’t think i will ever do track days, if anything, would just be a few laps, nothing hectic, should be able to put up with the 1.5

[Murray_Calavera]

10 minutes ago, LjB123 said:

Yeah fair enough, that’s unfortunate there isnt a 1 way from Nismo as I imagine for majority of people modifying their Skyline it would be a popular choice

For me its a weekend street car, driven once a week or for a whole weekend every so often, don’t think i will ever do track days, if anything, would just be a few laps, nothing hectic, should be able to put up with the 1.5

The nismo diff is adjustable, you can make it very tame (ramp up slowly) if that's what your after. When driving sensibly on the street, I'd be amazed if you could pick the difference between a 1 way and 1.5 way diff. The ramp rate on the other hand will have a dramatic impact on how the diff behaves on the road. 

As for being concerned that the factory diff will 'clunk out later' due to its age, that's not something I would be worried about. If its running well now, I'd expect that it will continue to run well as long as you keep it maintained with fluid changes as required. 

The main benefits you'll get from upgrading the diff are the ability to put more power down reliably. More control of the car mid corner and at corner exit. More predictability with how the diff engages/locks up, etc. 

[Kinkstaah]

There is no 1.5 way diff for Nismo, nor is there a 1.5 way diff at all, because all diffs that provide lock in both directions are by definition 2 way diffs.

Having driven my _real_ 1.5 way diff and a real Nismo 1 way diff, the difference is very noticable and will send you insane thinking you are troubleshooting the same part.

Observe the above diagram, then observe below:

This is sold as a "Nismo 1.5 way" but is clearly a 1 way that my mate had. 

This is my "Nismo 1.5 way" that is actually a 1.5 way (maybe - The ramps look pretty even) but it is what people refer to as a "2 way"

 

Nismo absolutely did (or used to) have different listings referring to different lockup types. From memory I saw it listed as "1 way" and "2 way" with no mention of the 1.5 way.

Go by Nismo's recommendations and what you want in a road car is the Nismo "1" way. Potentially the adjustable pro 2 way can be made to be very relaxed on deceleration, or you are going to have a very skippy time relative to your friends with the 1 way version of the "1.5 way"

This brought to you by a lot of pain and troubleshooting before opening the diff up. Get the right part numbers in your head from Nismo's page and get data like ramp angles and understand what they all are BEFORE BUYING A DIFF.

What people refer to as a 1.5 way is merely a 2 way, but with locking ramps that are less severe on deceleration.

45 degree ramps are the most severe, so a 45 on accel and 45 on decel will be a true 2 way. Something like a 45 degree on acceleration and say a 65 degree on deceleration will be a "1.5" way.

Something like 45 on accel and 90 degree on decel will be a 1 way. 90 degree ramps (which arent really a ramp) do not provide lockup. Look back at the differences between the two diff centers and you will be enlightened if not already

[GTSBoy]

All of the ^^ above is essentially true, except perhaps the semantics about there being no 1.5-way option. If you allow semantics to determine the argument, then any time the ramp angles are not even then it is a 1.5-way.

But as with genders, there are at least 73 different ways to set these things up, to the extent that it is probably a rainbow spectrum.

The Cusco doc I linked shows that Cusco's approach is to allow customers to select from a wider palette of ramp angles and clutch plate stacks and spring sizes and so on. So if you really really really want to get into the fine nitty gritty of optioning a diff, then Cusco's offering is probably the place to look.

Everyone just raves about the Nismo diffs because they are reputedly very civilised, but as you can adjust how these are set up also, it is difficult to reconcile those reports against reports like Greg's ^ where he argues that it was an aggressive bitch to drive with. Your piece of string might not be parallel to someone else's bag of skittles.

Meanwhile, after 4 years, I have my helical back in my car and I am loving it. I just wish I had some power to challenge it. Need to fix the dyno next.

[Kinkstaah]

5 hours ago, GTSBoy said:

All of the ^^ above is essentially true, except perhaps the semantics about there being no 1.5-way option. If you allow semantics to determine the argument, then any time the ramp angles are not even then it is a 1.5-way.

Ye, depending on the percentages of the angles they could be a 1.9 way, or a 1.1 way, or a whatever way. Or maybe more accurately you could call it a "2" way (and Nismo does!) because there is some degree of locking in both directions.

But I've never seen anyone talk about a plate diff in a skyline and use the term "ramp angle" and they absolutely haven't gone to Kazz and asked them what their ramp angles are, then compare them to Nismo, or Cusco etc. I think your post might be the first time I've ever seen someone consider a ramp angle or point out that it's customizable via Cusco!

My 2 way with its nearly 45 degree ramp angles (just going by the picture) was an absolute piece of shit. (below 10kmh, daily driving). The one you want, whatever the part number is is clearly the 90 degree 1 way one.

[Murray_Calavera]

15 minutes ago, Kinkstaah said:

My 2 way with its nearly 45 degree ramp angles (just going by the picture) was an absolute piece of shit.

I'd be really keen to hear about what you specifically didn't like about it and how the diff was setup. Oh and what oils you used in it too and if that made any difference either.

[Dose Pipe Sutututu]

If it's a car destined to do 99% street duties with 1% track duties, then don't get a KAAZ diff centre.

They are BRUTAL... I have one. I had to get it modified by a diff shop to make it a bit more gentle for the odd times it gets driven around on the street.

[Kinkstaah]

57 minutes ago, Murray_Calavera said:

I'd be really keen to hear about what you specifically didn't like about it and how the diff was setup. Oh and what oils you used in it too and if that made any difference either.

Do you like axle tramp? Every time the clutch is out and you're off throttle at 30kmh or less?

I tried lighter oils (Castrol's 90W?) and they were great, until they got sweated out in short order in street use.
I tried heavier oils (260W Cusco? Some Jap brand now) and it stayed inside the diff, but driving around town off throttle was just vile. On throttle was noticeably less actually. It got to the point where the clutch was in every single time I was off throttle. Forever. Everywhere. People inside and outside of the car noticed it, people asked me at work why the car was broken and all sorts of stuff.

I paid $1000 for the thing to be rebuilt and there was no issue found due to the fact the diff is designed to be that way. My car has always suffered from axle tramp mind you, trying to launch it at the edge of traction is pretty similar. Has all poly bushes (new) and pineapples have been tested in every configuration, nothing helped.

The VLSD and Helical are smooth as silk. My mate's S15 with the 1 way drove like you would expect. Minor skipping on sharp angles on throttle, silent off throttle. Better in every single way, though I will say on track the 2 way is very predictable and does NOT want to kill you on decel like people fear, or seemed to fear back in the day.

[Murray_Calavera]

@Kinkstaah yeah that does sound truly miserable. Have you had the chance to drive/ride in other skylines with the same diff though? Mine doesn't drive anywhere near like what you are describing. The only non-factory sounds mine makes is at really low speed, like doing a 3 point turn or navigating a parking lot, you get the inside wheel lock up sometimes like its a welded diff (doesn't happen all the time though and my diff is setup to be quite aggressive in the way it locks up) and it sometimes makes little diff clunk noises (not all the time though) but the wheel chirp and diff clunk isn't what I'd call bad at all, I really like the added character when it happens lol. 

[Kinkstaah]

I mean, the S15 has the same subframe as a R chassis, and had a Nismo diff in it. I'm confident that most people who think they have a "1.5" way diff just have a 1 way diff. I remain unconvinced unless they pull it apart and check.

I have heard the PRO nismo is far less harsh but I mean not many people have driven them all back to back. It was absolutely not a nice little race car skip (like the GR Yaris I had which had 2x Mechanical diffs in it), it was more like someone hitting something with a hammer in the boot. (Or bad axle tramp).

more BANG BANG BANG in slow, lound sounds than a skt-skt-skt of a locking diff. Interestingly, it was more skt-skt-skt on throttle.

I have a helical now and I love it. If it dies, I'll find some kind of wavetrac or 370z quaife solution or god knows what. Or maybe drive a mechanical I HAVE DRIVEN before I buy another one blindly :p

[Murray_Calavera]

@Kinkstaah I can 100 million % confirm that my nismo diff is the 1.5 way you are thinking of. 

I can still remember the exact moment when I forked out the $$ for a 2 way diff, looked inside and saw the uneven ramp angles and thought, f**k me, its a 1.5 way and not a 2 way. I was expecting that when I paid for a 2 way and all the nismo documentation, that silly certificate that nismo do, everything is stamped 2 way that I would in fact get what I thought was a 2 way diff, that is equal lock in either direction. Nope, full lock on accel and half lock on decell. 

I just accepted it and installed the diff, it was fine in the end. It turns out I really like the diff. 

I'm not going to strip the diff and take photos, but I can upload a photo of the silly certificate nismo do saying my diff is a 2 way if you like lol. 

I'm pretty sure I know the diff noise you are describing though. When I put a Cusco RS diff in my swift, it sounded like the diff was trying to smash itself out of the gearbox. It was an absolute nightmare. Fortunately the issue was solved by using Motul FF LSD gearbox oil, fkn expensive to change (I replaced it every 5,000k's) but worth the $ as it eliminated all the angry diff issues. 

[Dose Pipe Sutututu]

7 hours ago, Kinkstaah said:

have heard the PRO nismo is far less harsh but I mean not many people have driven them all back to back

Have driven 2x S15s with the Nismo Pro (adjustable initial torque, both on low) and 1x S15 with an older style Nismo diff without option to adjust (old Intima / trak-life S15) and there's a big difference. The latter would behave like my KAAZ diff.