30S And Taller Rwd Diffs ?

[Dale FZ1]

If you use a GTR spec diff centre then you'll want a complete GTR rear assembly. Half shafts and bearing hubs are the issue with making it work in a ECR chassis.

It's a bit clearer when you look at a Cusco/Kaaz fitment list because those 6 bolt output flanges signify the beefier shaft size and splines of the GTR.

Adrian playing with these things is much like the older Datsun stuff. You can mix and match. My diff runs the original ECR housing, a R32 GTS4 crownwheel and pinion, and the swanky finned alloy rear cover plate. Careful measurement of the housings showed identical internal clearances so the shims were dropped in as a matched set for correct preload. Worked a treat.

R33 2wd used 3 channel ABS with slightly longer snout on the housing, and it appears that anything 4wd including the R32 GTS4 ran 4 channel.

And the S13, Cefiro, and Laurel gear appear to have different mounts so those housings won't work on your R33.

It can involve a bit of playing around to get what you want but no real problem once you know what bits fitted to what model. Same as Datsun.

[Simon-S14]

you can just put the GTR centre, halfshafts and hubs into your 33 without changing the subframe or the uprights.. it all bolts straight in. easy as.

and yes.. you can mix and match. im about to put GTR LSD from my 4.1 r32 gtr diff into a 4.3 r200 diff and run the GTR halfshafts. as its easier tyo change ratio by changing housing rather then CW&P

as for S13, R32 etc diffs. they will bolt into an R33, but you need to use the bolts that bolt it in... not the r33 ones. and you need to change the rear hat.

you'd be suprised what can fit in what.

[jet_r31]

Makes me wonder why anyone would bother to slip in a RB30 if you then counteract the improvement by reducing the torque multiplication at the wheels by using a taller diff. It might make for a more relaxed "feel", but the car will accelerate less quickly in any gear.

Adrian the character of the car is transformed by use of the longer stroke bottom end. Stay with the stock 4.11. I've gone the other way and use a 4.375 ratio. Means first gear is basically for parking or creeping in traffic or pits. Track acceleration from about 60-190km/h in 3rd and 4th is really solid, and the car is geared to pull 250km/h in 5th ie. has no lack of top end speed.

Depends on use of the car of course, but the 4.11 gearing still suits the car very well.

On most street tyres the car will accelerate quicker, i've had 4.11, 3.9's and 3.45's..3.45s where so much quicker at any speed with 370rkww. I've done it with my other turbo cars aswell, was always slower in theory, faster in reality. Radials are very picky when it comes to changing road speed and don't regrip easy, i just find the taller gear makes the transition around peak torque a lot smoother and you have more road speed. I know Cubes on here used to disagree with me yrs ago about this same thing , after driving his Rb25/30 for a while, he changed his mind and agreed with me totally

cheers

darren

[discopotato03]

Thanks for your input jet , what do you think was the best general purpose diff ratio you used?

Part of the basic question for me is can I better use the torque my engine has if I load it up a bit more for the same road speed .

What I find is that both the Evo and the GTS25T make good torque but at part throttle with even low revs in low gears they seem to go nowhere unless at WOT , so the only option is to short shift them everywhere trying to find enough load to use the good part throttle torque they have .

The idea behind slightly taller gearing is to have a bit more load on the engine from a little less gearing reduction , its not about moonshot speeds at the redline in 5th gear .

I understand the bit about having slightly improved traction control when the engine comes onto boost and the torque multiplies over a narrow rev range . If the gearing is taller the process should take a little longer and I think its because the torque multiplication not ganging up as quickly with the gearing reduction and overwhelming the available traction .

I'm not Robert Godard and I think the potentially better fuel consumption comes from a slightly more open throttle at highway speeds at lower revs - a bit better cylinder filling meanig a slightly higher dynamic CR . If your 5th gear is going to be a real overdrive its probably not realistic to expect it to be usefull at less than highway speeds - meaning 80-90+ .

Anyway unknown to me but I find it impossible to believe that a 20% increase in engine capacity for a 5% (3.916) or 11% (3.692) increase in gearing wouldn't be better everywhere than the std RB25 4.11 combination . Should have more torque everywhere and 5-10% more load for the torque to push against .

Actually if you crunch numbers compare a 2L R32s 4.363 gearing with a 2.5L R33s 4.111 (25% bigger engine) the gearing difference is 6% so if you follow the trend its likely a 3L R33 would have had 3.916 (+5%) gearing at least outside Japan .

If you want to compare any two diff ratios divide the numerically smaller into the larger and mulpiply by 100 ie 4.11 / 3.916 x 100 = 104.95% .

My suggested three litre 3.916 ratio is 111.34% - 11.3% taller than the two litres 4.363 diff ratio . Had the comparison been 3.692 to 4.363 the increase is 18.2% for a 50% increase in engine capacity .

I wonder what the final drive difference is between a 3.6L and a 6.2L Dunnydoor , cheers A .

Edited July 5, 2012 by discopotato03

[mambastu]

I really can't see why you'd want to go from a 4.1 to a 3.9 (or worse) unless it was for economy reasons or you needed to attain a higher speed in fifth (assuming you could actually pull it) or you had a vastly reduced available rev range compared to the original 25/26 - say 6500 rpm rev limit.

A few years ago I fitted a 400bhp RB25 to my UK 200SX (180SX outside europe) which had a 3.9 diff originally. Ran it like that for a few months and then swapped to a R33 GTS-T 4.1. A seemingly small change but the car accelleratedso much better through the rev range with the 4.1. I'd personally run 4.3's on my new RB30/26 if I could get hold of them for my BNR32.

I also know someone with a 3.6 final drive in a 600bhp 180sx and that ruins it IMHO. Really doesn't go the way it should. Lots more traction yes - a lot less accellerative too though unfortunately.

Edited July 5, 2012 by mambastu

[discopotato03]

I thought it was possible if you could get the R32GTS4 diff bits .

The reason is I'm not into street racing and I don't drive street cars flat out everywhere . Also as I keep saying these cars are traction limited and what I like is high average torque everywhere .

I'm not so sure a 400Hp Rb25 is going to pull well down low , some will but a lot depends on how you went about getting 400 and what that did to its low down performance . Same for the 600Hp RB30 . I think with a bit of thought an RB30 designed to pull from nowhere revs will have strong part throttle torque and acceptable full throttle power . You do realise that a 5% difference is 50 revs per thousand so 150 revs at 3000 .

A .

[KiwiRS4T]

I put a GTR diff in my Stagea for two reasons:

To get the stronger 6 x 1 axles

and to get a decent LSD to replace the viscous Stagea one. You don't need to change the outside hub carrier or whatever they are called - if you do the positive is they are aluminium and therefore lighter and the negative is that you then need fork ended shocks so have to change.

[discopotato03]

I'm sorry now I didn't post another link to a pictorial of a GTR diff/axles/hubs conversion into an S13 . They just removed the S series bits and bolted the above GTR bits straight in . The only mods are because S13s have the small plain front diff mounting holes and GTRs have the later rubber bushed system meaning larger holes in the front diff mounts to fit these bushes .

Other than this and the GTRs unique companion or front input flange it just about falls in .

Its good to see that the steel uprights or knuckles if you like take the larger spline size GTR hub bearing assembly and I certainly wouldn't be changing to the aluminium one in a road car . Can't see the sense in having to do rear struts just for the ally knuckle .

Its seems obvious than a late R200 is an R200 is an R200 . The only major things that are going to trip you up are the nose lengths (front ABS/non front ABS) and the stub axles because they have to suit the diff centers splines/lengths and obviously your choice of half shafts .

I cant see anything stopping you using a GTR mechanical LSD in any of these diffs provided you use the matching stubs half shafts and big spline hubs .

What will limit your choice in a 4WD car is available front diffs to match the rears ratio to .

For a RWD R33 using GTR bits seems easy because 99% of it looks like it goes straight in - well to a non ABS car like mine anyway . If you found a non ABS diff in whatever ratio you like I reckon a GTRs LSD center would go straight in and then you just work out from the GTR stubs to the hubs .

Your choice of ratios and in fact if you used your own diff as a basis it all goes together by the look of it .

A .

[discopotato03]

GTR diff in S13 Link . http://w3slide.blogspot.com.au/2011/09/gtr-rear.html

A .

[Simon-S14]

yup.. easy

[jet_r31]

if it was my car Id use the 3.7's ,disco as simons14 used on his mates car.

cheers

darren

[Simon-S14]

yeah totally transformed that car... the 32 wanted to bake tyres in most gears on the street and wet weather was damn hard to keep it straight haha. My mate isnt the kind to muck around on the street, he wanted more grip and acceleration. the 3.7's made the world of a difference.

[discopotato03]

I haven't had time to read right through this thread http://forums.hybridz.org/index.php/topic/64241-short-nose-r230-and-r200-info-and-why/ but it looks to have useful info on some late short nose USDM R200s and R230s . It probably answers the questions about the larger stub (6 hole) and axle size used in GTR spec R200s and I'm guessing Z32 TT R230 diffs .

A .

[WHITER33GTS-T]

Does anyone have 3.5 diff gears laying around to suit a R200...?

[KiwiRS4T]

Does anyone have 3.5 diff gears laying around to suit a R200...?

That would be R34 GTR diff - I have been trying to source one for a couple of years! There's one here but they won't post - may suit you:

http://www.ebay.com.au/itm/Nissan-R34-GTR-Rear-Diff-Complete-/320980280643?pt=AU_Car_Parts_Accessories&hash=item4abbea6543

[WMDC35]

i had a f/lift c34 rb25de & re5 auto which had a 3.5 r200

[WHITER33GTS-T]

That would be R34 GTR diff - I have been trying to source one for a couple of years! There's one here but they won't post - may suit you:

http://www.ebay.com....=item4abbea6543

I did see this but wont freight.

Stagea diff would be an option... Does anyone have one..?

[KiwiRS4T]

I did see this but wont freight.

Stagea diff would be an option... Does anyone have one..?

Tallest Stagea one is only 4.083 - effectively the same as 4.111

[Guilt-Toy]

there must be a 3.5 diff that comes out in a r32 or something similar... the diff in my r32 that i purchased here.. the diff was crazy... 4th gear will spin the rear wheels to 260km/h.

when i removed the diff it looked like a GTS-T diff of some sort, because it did not have the GTR type tail shaft setup that the gtr's do and it was a viscous because i shimmed the diff.

it was with my 380kw rb30det setup, and the car really did suck to drive, i hated it. off boost it was just boring for me, you couldnt get the wheels to spin or have any fun off boost you had to always load up the engine before anything interesting happen. when on boost the gears went forever and it was just boring.

when driving the car before i realised the diff gears were out the car was just dangerous, at that kind of speeds in 4th gear i slowed down and wondered why the car felt soo unsafe, i only worked it out when on the dyno and i saw the wheel speed at the top of a dyno pull when i started to wonder wtf is wrong.

and drifting that car SUCKED, had to drift in first gear because dropping the clutch in second gear was impossible, the car would go sideways but because the wheels are spinning sooo fast 140km/h + you just put out soo much smoke and then lose it because of the high wheel spin speed at such slow speeds.

i took the diff out and installed a r32 gtr diff, and welded it. all is good now the car is awesome to drive.

my 350z with a rb30dett with rb25det box also has a 3.5 ratio, this one i don't mind so much because its a daily driver, but same goes with r32.. i dont ever bother trying to do any kind of drifting or burnouts as it just puts too much strain on the drive train and its just plain old stupid... i already broke the diff in the 350z and i am looking at changing it back to a 4.11:1 to match the 25 box as these things had a 6 speed standard.

however the good thing is because i do alot of highway driving, i can cruise in 5th gear doing 155km/h for hours on end without any overheating issues or any problems at all, get great fuel economy also... i drive to work which is a 150km trip, 70% of that i am sitting on 155km/h and im reving at 3500 or so rpm, in the skyline it would be at 4.2k + (diff is a normal 32gtr one now) ??

if anyone can help me to get a 4.11:1 or even 3.9 into my 350z that would be nice.

I would seriously not change the diff gears unless you want better fuel economy and dont care about enjoying your car the way it should be enjoyed...

maybe if you can change the 5th gear cog only to drop the rpm down would be a better option too.

don't change it.. if your adding extra torque then.... ...... .. "enjoy it, don't destroy it!" IMHO

[discopotato03]

I partially agree only with an RB30 I think a slightly taller diff ratio and a shorter 5th ratio would make it nice .

I always thought the 0.76 5th was a big jump over a direct 4th and it may need to be this way if you wanted to drop back to 4th and boot it - as in get enough revs up to haul . Thats with a std capacity RB25 or 26 BTW .

I still think the revs needed at 110 km/h are too high with the standard gearing but without a closer spaced 6spd gearbox its always going to be a compromise . They obviously knew this and fixed it on the later Z cars .

I don't suppose the 6 cog can be grafted on an RB block ?

A .