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R34 Gtt Diff Recommendations / Would It Take Gt-r Centre?

V28VX37
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V28VX37 Veteran

V28VX37

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7 hours ago, GTSBoy said:

Listen to me very carefully.

The H stands for Helical.  The V stands for Viscous.  Those two diff centres have different length stub axles.  Actually, I think it is only one of them that is different.  But anyway, if you have the stub axles that fit a helical centre you cannot fit them into a diff centre (say, the 1.5 way you're looking at) if it suits a viscous centre.  Likewise, if you have the stub axles to suit a viscous centre, you cannot fit them into a centre intended to replace a helical centre.

THAT is why there is a different part number.  The diff centres actually are different.  However, and this is important.  BOTH centres (both part numbers) will fit pretty much ANY R200 housing.  So long as you have the stub axles to go with them.  Now, if you need to obtain stubs to suit a viscous centre, that's easy.  They're lying around in any wrecker.  But if you need to obtain stubs to suit a helical, then it might take a bit more searching. The reason?  Because there are so very very few R34s out there with helical diffs.

That's right.  Most R34 manuals have a viscous diff.  If you look in the Nismo guide you'll see the earlier cars are viscous.  I should know, I bought one (hoping it was helical).

 

Short answer, As you have stated that you know your diff is viscous, then I promise you that any centre to suit an originally viscous diff will fit your car.  What I cannot promise you is that the 1.5 way centre you'd like to buy suits a viscous or a helical (well, you know, the stub axles).  But there's probably no-one except Nismo ever made a diff to replace the helical. Most people with a helical would not replace it with a mech diff anyway.

Thanks yet again GTSBoy, that's great!

I have the viscous diff so I'm guessing that I should be able to just reuse the existing stub axles, yes? Given that the diff centres are the same dimensions.

Also I tracked down the part number on the actual box, it only says 38420-RS015 , no -A or -BA. This supports your point above that the only difference is the stub axles, the centre is the same.

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V28VX37 Veteran

V28VX37

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So I missed a critical line in the Nismo catalogue:

  • Application          1.5WAY Part no.    Diff type (axle)   Final ratio   
  • ~’00/8                  38420-RS015-BA  R200V/R200H  4.083/4.111
  • M/T車‘ 00/8～      38420-RS015-A    R200H              4.111
  • M-A/T車‘ 00/8～  38420-RS015-BA  R200V              4.083

So judging by the part number I'm guessing that pre-08/2000 cars all have the viscous centre.

Therefore, contrary to popular belief, a lot of R34 GTT manuals also came with a viscous diff, just like the autos. I probably missed this in an earlier post..

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V28VX37 Veteran

V28VX37

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For anyone else looking here's some part numbers:

Nismo GT LSD for R34 (off the Nismo 2016 catalogue):

27930122490_5f196e7cd3_b.jpg

Nismo GT LSD Pro for R34 (off the Nismo 2016 catalogue):

28133361361_3f3264c9c2_b.jpg

Kaaz for R34 (off eBay):

28210641175_1498291019_b.jpg

Looks like the model year ranges are not entirely consistent so caveat emptor.

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Kinkstaah Grand Master

Kinkstaah

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On ‎7‎/‎8‎/‎2016 at 6:44 PM, V28VX37 said:

Too slow, missed out. Greg I hope you got it!

Yes indeed I did lol.

I got it right as I saw GTSBoy's post >.>
I am a bad person.

But yes - ONLY the R34 Series 2 manuals have a helical from factory. This is 8/2000 to 2001 models (not many in AUS but they do exist). I have a series 2 myself but it's an auto. Also fun, many many plugs and sensors are different to the S1 because.... reasons?
All signs seem to point as GTSBoy said, the center is a different part number only because it has to mate to the helical half shafts.

I suspect the GT Pro model number is the same for all cars as it comes with half shafts to suit. But again this is a suspicion there.

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V28VX37 Veteran

V28VX37

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Haha I knew, well played sir, well played. Keen to hear how it goes, especially with auto on decel when you can't clutch in if the going gets hairy.

Now, what do people think, is there any point in going 1-way Nismo over the OEM viscous unit?

The car is 95% street / 5% track (grip) so a 2-way would be too aggro but I'm guessing a 1.5-way would be a happy clunky compromise...?

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GTSBoy Grand Master

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3 hours ago, V28VX37 said:

Now, what do people think, is there any point in going 1-way Nismo over the OEM viscous unit?

Oh hell yes.  Face it, viscous diffs are either full time open, open as soon as you give them enough power or soon to be full time open.  As such they have no useful purpose behind any engine that can make enough power to defeat them.  Which is pretty much anything better than stock.  A 1-way diff at least gives you traction under load.

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V28VX37 Veteran

V28VX37

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Ok after much deliberation I have the Nismo 1.5-way on order from Japan ( 38420-RS015-BA ). Will report back once it's in.

Greg's just got his installed too, perhaps he can share some thoughts :)

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Kinkstaah Grand Master

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It would appear I had the best viscous LSD in existence because this Nismo is worse in every way (currently).

I would however wager over time my viscous would flog out with 400rwkw and this Nismo will break/wear in. But currently having it skipping while going around an 80kmh bend isn't really providing more grip for me, given my Viscous didn't actually single spin at all :P

Even though I had the Viscous diff, and my Nismo box had the Viscous part number on it, I was told I absolutely needed the half shafts as the center in the box would not fit my original half shafts. So no light shed there as to which center to actually buy.

Mine is the GT, not the GT Pro. Would recommend the GT Pro, if only so I could make it lock less (for me)

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GTSBoy Grand Master

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The viscous diffs are actually the orphans when it comes to stub axle lengths.  Because of the details of the insides of the viscous centres, they end up with one side short and one side with a quite long spline insertion distance, whereas nearly every other type of diff has either even or very close to even lengths.

The Nismo diffs actually come with 2x stubs that would suit an open diff (in terms of length, not the flanges, because all the open diffs were for limp wristed NA cars and they all have 3x2 bolt flanges!).

Greg, you should probably add some of the friction modifier additive to your oil to see if you can calm it down.

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V28VX37 Veteran

V28VX37

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The Nismo diff is going in tomorrow, yay. Here's the type and part number: Nismo Mechanical LSD GT 1.5way for R34 GTT (38420-RS015-BA). Hopefully it goes in without much drama.

What's the correct procedure for running one of these in?

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V28VX37 Veteran

V28VX37

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On 7/7/2016 at 11:43 PM, GTSBoy said:

Listen to me very carefully.

The H stands for Helical.  The V stands for Viscous.  Those two diff centres have different length stub axles.  Actually, I think it is only one of them that is different.  But anyway, if you have the stub axles that fit a helical centre you cannot fit them into a diff centre (say, the 1.5 way you're looking at) if it suits a viscous centre.  Likewise, if you have the stub axles to suit a viscous centre, you cannot fit them into a centre intended to replace a helical centre.

THAT is why there is a different part number.  The diff centres actually are different.  However, and this is important.  BOTH centres (both part numbers) will fit pretty much ANY R200 housing.  So long as you have the stub axles to go with them.  Now, if you need to obtain stubs to suit a viscous centre, that's easy.  They're lying around in any wrecker.  But if you need to obtain stubs to suit a helical, then it might take a bit more searching. The reason?  Because there are so very very few R34s out there with helical diffs.

That's right.  Most R34 manuals have a viscous diff.  If you look in the Nismo guide you'll see the earlier cars are viscous.  I should know, I bought one (hoping it was helical).

 

Short answer, As you have stated that you know your diff is viscous, then I promise you that any centre to suit an originally viscous diff will fit your car.  What I cannot promise you is that the 1.5 way centre you'd like to buy suits a viscous or a helical (well, you know, the stub axles).  But there's probably no-one except Nismo ever made a diff to replace the helical. Most people with a helical would not replace it with a mech diff anyway.

 

On 7/18/2016 at 11:42 AM, GTSBoy said:

The viscous diffs are actually the orphans when it comes to stub axle lengths.  Because of the details of the insides of the viscous centres, they end up with one side short and one side with a quite long spline insertion distance, whereas nearly every other type of diff has either even or very close to even lengths.

The Nismo diffs actually come with 2x stubs that would suit an open diff (in terms of length, not the flanges, because all the open diffs were for limp wristed NA cars and they all have 3x2 bolt flanges!).

Greg, you should probably add some of the friction modifier additive to your oil to see if you can calm it down.

 

Just to close the loop, the Nismo Mechanical LSD GT 1.5way for R34 GTT (38420-RS015-BA) comes with plug and play stub axles for the R200 housing (with VLSD) found in the early ER34's. Mine's a 1998 model, originally auto but later converted to manual.

In terms of running in, the story sage continues here: http://www.sau.com.au/forums/topic/466340-nismo-gt-vs-gt-pro-run-in-time/ . Many fun times have been had.

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