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Pedro

3.9 or 4.11 ratio

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Guys,

 

I am considering a R200 lsd for my 260z with the goal of long term putting a RB25 NEo0 and RB25 box in the beast. Right now i am driving it as is with the L26 and will be for the next year or so.

 

I was thinking of doing the LSD now though (i mean it has to happen sooner or later). For a mild RB25, i.e. 160-200 kw atw, what ratio would better suit the car ~ 3.9 or 4.11?

 

I am aware that the R34 skyline comes with a 4.11 but have noticed many prefer to run the 3.9. Any comments appreciated,

 

Peter.

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After having an RB25DE and gearbox in a zed, I'd go for the 4.1. If you plan on doing any sort of club / track day events, go for the 4.1. I was using a 3.9 LSD and found the ratios to low; for example at Sandown, I'd never use 5th! By the time I'd reach the 150m brake marker before the first turn, my shift light would just about be on. Not sure how much more torque the turbo's run but that's what I found..

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i got 4.4 in mine but 4.1 or even 3.9 would be a better option. with rb25det u got lot more tourque even going down to 3.7 in a light s30 rb25engine wont have any issues moving it. though u be getting to some fairly high speeds.

 

i got rb20det with lot less tourque with bigger turbo. 4.4 seemed logical but i find changing gears very regularly.highway driving also bit too low,  rpm vs speed is bit high in 5th chews fuel.

 

but off the line gives wrx run for their money pitty i have to do an extra gearchange.  8)

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so is it reasonable to assume that 4.11 is optimal, followed close second by 3.9?

 

car will be mostly used on the road, doubt it will see the track often...

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I can't tell you how it is on the road as my car is not assembled but for my RB conversion I will be using a 4.11 lsd.

 

So much so that I sold my 3.9 lsd and picked up another 4.11 open and another lsd center for a spare. Would like to get a 4.4 also for one of the tight tracks here in nz

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wanna swap NZ for a 4.1 or 3.9  ;D

Yes can do that but shipping is going to kill any swap they are heavy little buggers (R200's that is as this is what I have)

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Where you thinking of sending the whole diffs over? Just swap gearsets.. a lot lighter than a whole 38 kg of R200.

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Yes can do that but shipping is going to kill any swap they are heavy little buggers (R200's that is as this is what I have)

 

true yeah mines R200 LSD  long nose out of R30 RS turbo skyline. very clean and good diff.

 

zedman. i got 3.7 gearsets and can get 3.9. prob is to get them replaced by someone costs lot more than its worth expecialy finding out it wasnt a good result. 

 

though i know the procedure to set one up but wont be game to risk $1500 lsd diff for experiment.

 

do have a damaged R200 short nose LSD out of S14. damaged gear set. so was going to remove the lsd part and shove it in one of the 3.7 long nose open wheelers.

need an LSD for 240z anyway. so 3.7 looks like it will be a good compromise with SR20det infront of it.

not sure if ill be game to drive it to 260+km/h in a 39yo old car.

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Where you thinking of sending the whole diffs over? Just swap gearsets.. a lot lighter than a whole 38 kg of R200.

good idea but I have not got the correct tools to remove the pinion = $$ at diff shop to get it out - but I would be happy to do that with either 4.11 or 3.9 for a 4.4 crown/pinion

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RBZ, You may find the splines out of the S14 LSD centre are different from the R200 longnose for the zeds. I'm about 80% sure of that. Count and make sure first.

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yeah i know its actualy the viscous type so the stock driveshafts are useless

 

From memory i think the splines are same just not long enough to reach the center.could be wrong on this. therefore have to use viscous type cv which is no big deal as was planning in doing so anway. 

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The standard ratio for the RB25DET was 4.11 and I liked it.  I have a 3.7 atm and its not enough so i got a 3.9.  Will have to see how that goes.

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I have decided on 4.1... that way when i get to the RB conversion the car will be ready. in the meantime it will be running pretty short with a 260z box, but should be fun..

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