30S And Taller Rwd Diffs ?

[discopotato03]

Hi all , I've looked a few times and not seen anyone come up with a way to get a 3.9 or 3.7 ratio gear set into a GTS25Ts diff .

A few threads I chased quoted about 120-130 revs difference per 1000 revs at 100 km/h between 3.7 3.9 and 4.1 .

I imagine an RB30DET with a compression ratio of around 9-9.5:1 should easily pull 5-10% taller gearing since the 20% increase in capacity in theory should give 20% more torque . SKs way of explaining the capacity increase is to say that everything happens 20% earlier in the rev range than a 33 25DET .

Anyway has anyone found a way to get 3.7 or 3.9 gears into the back of their RWD R33 and is their speedo drive pinion gears to suit ?

Also I have to work out the slight difference circumference wise with 235 45 vs 245 45 17" tyres . The 245s were always more exy because they appear to be a less comon size . I should also check 255 40s to see where the rolling diameter is .

Thanks in advance , cheers A .

[KiwiRS4T]

The speedo is the easy bit. If you can't get the right drive gear you can just get a Jaycar kit to modify the signal.

I can't see the point of going from 4.1 to 3.9 as the difference is quite small. I have an RB30 in my Stagea (with 4.1 GTR diffs and 255 40 17 tyres) and cruising at 110km/hr is 2700 rev/min and I would like to bring it down quite a bit so I have the 3.545:1 front diff from an R34 GTR and am looking for a rear one to go with it. I have a .63A/R exhaust on my 3540 and don't fear lack of response. With a 2wd it would be easier as you have the chance to put the 9in diff from the GTT Z car which is also 3.545:1

If you really want a 3.7 or 3.9 you will find a few in this list:

http://www.nismo.co....f/lsd_price.pdf

[jet_r31]

i'd want a 3.45 ish diff with a RB30, even high powered 300+ rwkw RB25's should really have them IMHO, kills of the torque

as boost ramps hard on, makes it a lot easier to get traction and modulate throttle under wheelspin aswell...

cheers

darren

[Dale FZ1]

i'd want a 3.45 ish diff with a RB30, ... kills of the torque

...makes it a lot easier to get traction

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.

[XKLABA]

The speedo is the easy bit. If you can't get the right drive gear you can just get a Jaycar kit to modify the signal.

I can't see the point of going from 4.1 to 3.9 as the difference is quite small. I have an RB30 in my Stagea (with 4.1 GTR diffs and 255 40 17 tyres) and cruising at 110km/hr is 2700 rev/min and I would like to bring it down quite a bit so I have the 3.545:1 front diff from an R34 GTR and am looking for a rear one to go with it. I have a .63A/R exhaust on my 3540 and don't fear lack of response. With a 2wd it would be easier as you have the chance to put the 9in diff from the GTT Z car which is also 3.545:1

If you really want a 3.7 or 3.9 you will find a few in this list:

http://www.nismo.co....f/lsd_price.pdf

See if you can organize some to grab this for you and send it over

http://www.ebay.com....=item4ab19d4f69

Taller diff gears on a high powered RB30 are a good idea, lowers wheel spin, reduces gear changes and generally takes better advantage of the extra torque, especially on a RWD car

the 4.3 ratios were for the RB20 GTS4 with 154kw and 265nm, the R32 and 33 GTRs have 4.11 with a RB26 and 206kw with 368nm of torque, so 3.9s or even 3.55s on a RB30 with 400fwkw and lets say 600+nm is only logical, my opinion

[R31Nismoid]

Al still has 4.11s in his RB30, the acceleration of the car is phenominal (which is in the ballpark of where you are heading isnt it disco??).

Then he is running 18s i think, not sure of the tyre. wouldn't be far off coming up on boost in 5th on a FWY, would be nice to put around on for sure even with 4.11s

Funny all this talk about taller diff gears and a mate with a blown LS1 has recently put 4.11's into his car... Make more torque than any RB even will

[discopotato03]

Um no , limits to how fast you can drive a street car particularly a traction challenged one .

No my thoughts were about being able to use the extra capacity to make my car easy to drive under all conditions - more flexible as in can pull any gear at just about any engine speed . I'm actually trying to guess what Nissan would have done had they used an RB30/25DET in an R33 Skyline .

I have a feeling it would have been the 3.7 or 3.9 based on more torque at low revs than an RB25DET .

Anyway my aim wouldn't be 350 Kw if I went down the RB30 road , probably more like 270 (Gt3076R) but able to be flexible and strong without having to wind it up . Sort of larger almost NA like power delivery . Lower cruise revs at 110 would be good and I reckon a 30DET should be able to go most places at 26-2700 revs provided its static CR was in the 9-9.5 range and it had std or something mild like 256 Poncams .

Back to Factory I think slightly lighter VLTs had 3.45 diff gears with admittedly wider gearbox ratios and our porky R31s had from memory a 3.7 or 3.9 Borg warner diff .

A .

[JonnoHR31]

Manual 31s were 3.7 and autos were 3.9. Apart from 5th gear all the box ratios are the same as 32 and 33.

[R31Nismoid]

Um no , limits to how fast you can drive a street car particularly a traction challenged one .

No my thoughts were about being able to use the extra capacity to make my car easy to drive under all conditions - more flexible as in can pull any gear at just about any engine speed . I'm actually trying to guess what Nissan would have done had they used an RB30/25DET in an R33 Skyline .

I have a feeling it would have been the 3.7 or 3.9 based on more torque at low revs than an RB25DET .

Anyway my aim wouldn't be 350 Kw if I went down the RB30 road , probably more like 270 (Gt3076R) but able to be flexible and strong without having to wind it up . Sort of larger almost NA like power delivery . Lower cruise revs at 110 would be good and I reckon a 30DET should be able to go most places at 26-2700 revs provided its static CR was in the 9-9.5 range and it had std or something mild like 256 Poncams .

Back to Factory I think slightly lighter VLTs had 3.45 diff gears with admittedly wider gearbox ratios and our porky R31s had from memory a 3.7 or 3.9 Borg warner diff .

A .

As it would've been a Jap market, probably would have kept with the 4.11s

If it was a ADM then the gears probably would've been changed.

Al has 300-320rwkw with a GT3076 as well, so very similar setup. Maybe shoot him a PM and ask what RPM's he has what its like with a 30?

[KiwiRS4T]

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.

With only 280AWKW so far my (target 300 -330) my car pulls strongly from 2000 rpm in top so I don't think the improvement has been counteracted. It will accelerate just as fast but of course at any given speed might be in a lower gear than with a 4.1 final drive. With a 3.545:1 first gear will be usefull again and will be able to pull more speed in each gear - handy as I will be limiting revs to 6500 - 6700.

See if you can organize some to grab this for you and send it over

http://www.ebay.com....=item4ab19d4f69

Thanks I'll check it out!

[discopotato03]

I seem to remember the RB25/26 turbo gearbox ratios being slightly better than the eariier smaller NA 5spd boxes . An annoying thing Nissan used to do was to have a big jump first second in those NA6/4cyl boxes - something like 3.3 - 1.91 and I think that had a lot to do with people wearing out or breaking 2nd syncros if they slammed 2nd gear all the time .

It used to shit me up the wall 20yrs ago when I was playing with Bluebirds and stroked L series donks with sidedrafts and later FJ20ET engines . I had Stewart Wilkins build me a 5spd based on Aus spec 260Z ratios converted to Warner (brass) syncromesh . First second was 2.9 - 19 and that was really good .To me the 25T box feels like is was designed to be short 1st to 4th and a bigish jump to that 0.759 5th .

Actually thinking about if a heavier R33 GTR with 70 more lower CR ccs can get away with 4.1 diffs you'd think a 20% larger engine pulling 100+ kilos less could pull slightly taller gearing .

I can see what your saying about JDM cars and their speed limits and traffic volumes . They probably don't cruise interstates at 110 for hours on end very often .

Ultimately gearing is a trade off of street drag vs overall usability and for me I'd like to lean towards usability , I think with an RB30 you can do this if the engine is not a high rev drag screamer . I'm not that interested in traffic light drags or going flat out everywhere , to me a bigger engine is all about doing everything more effortlessly basically same performance with less revs or more performance with the same revs as the standard size engine .

Anyhow I think 3.9 or 3.7 would suit me for how I drive most of the time in Sydneys suburbs .

A .

[JonnoHR31]

1-4 is the same in all of them. 5th and reverse are the only gears that are different between 30, 20 and 25/26 with the 30 having the shortest 5th, 25 the longest and the 20 in the middle.

for a rough reference with a 25 box, 3.9s and 245/45/18s at 100km/h I'm doing 2500rpm.

[KiwiRS4T]

R32 & 33GTR R34 (6 sp Getrag)

1 3.214 3.827

2 1.925 2.360

3 1.302 1.685

4 1.000 1.312

5 0.752 1.000

6 0.793

Sorry won't keep the format - R32 and R33 GTR the same R34 in RH column.

[discopotato03]

No first and second are very slightly different , The big box 1st is 3.2 vs 3.3 and second fractionally shorter .

Things like Aus spec 260Zs had a 2.9 1st and my Evolution 6 is 2.75 , admittedly with 4.5 diffs , in 1st .

Obviously its easier to change diff gears than individual gearbox ratios .

For the record what do aftermarket close ratio gearsets use ratio wise ?

A .

[KiwiRS4T]

e.g.

Auto Gallery Yokohama gearsets (rebuilt boxes).

yes there are upgraded synchro boxes available. I have one in my 32. made by auto gallery yokohama (Koizumi)

it's a good box. i've used it for about 5 years with no drama.

you can do a mix of the OS box and AGY bits.

DJR81, they have their own double cone synchros. they also do various different close ratio gear sets too just like OS Giken.

they do a nice transfer case overhaul too.

<a name="content2">

ratio choice:

version 1

１= ２,６１１　　　　　　　

２=１,７３３　　　　　　　　　

３=１,２８９　　　　　　　　　

４=１,０００　　　　　　　　

５ =０,７５２　　　　　　　　

OR (standard ratios I think?):

１　３,２１４　

２　１,９２5

３　１,３０２　

４　１,０００

5　０,７５２　

They have some optional 5th gear choices too:

5 ０，８４２

5 ０，８２６

5 ０，８００

version 2 close ratio box is:

１　１,９０３

２　１,４７６

３　１,１８６

４　１,０００

５ choice of the 3 above.

[discopotato03]

I'll have to ask Stewart Wilkins if there are suitable crown pinion sets with the right sized crownwheel bolt sizes that will go int an R33s housing . Generally dramas surround getting the pinion height right and backlash within spec . He may also know if suitable speedo drive gears exist to make that straightforward .

The earlier long nose R200s from R30 R31 and various Zeds were easier to get suitable ratios and they mounted off the same nose and removable rear cover housings .

A .

[Adriano]

r34 gtr diff is 3.5;1

[Dale FZ1]

e.g. Auto Gallery Yokohama gearsets (rebuilt boxes). yes there are upgraded synchro boxes available. I have one in my 32. made by auto gallery yokohama (Koizumi) it's a good box

I like the look of those options there. Bob was it difficult to source?

[Simon-S14]

Aust spec s14 manual SR20det is 3.7... dime a dozen too. will bolt straight into an R33 and into anything else with ease,.

mate of mine was having traction issues with 4.3's and rb30det powered r32.. so he put my 3.7 in and i grabbed the 4.3 off him... his was insane.. 2nd gear acceleration was massive as it just hauled instead of wheel spinning.

[discopotato03]

I did some searching around to to see if thats right about S14 or 15 diffs bolting straight into R33 GTS25Ts .

I need to update my information on these later short nose R200 diffs .

It seems there are differences in the half shaft adapters and these can be 5 or 6 bolt , sounds like R33s are 5 bolt .

I looked at lots of pics and another difference seems to be ABS/non ABS because of the pinion sensor . Is the difference a slightly longer nose needing a slightly shorter tailshaft on ABS cars ?

Also , this is a link to a site showing a pic of a couple of short nose R200s and note the size of the front mounting "ear" holes .

http://forums.240sxone.com/showthread.php?t=3880

I suspect the small ear hole one is an S13 diff and the big hole one next to it takes bushes to reduce NVH on S14s ?

It sounds possible to coble together a 3.7 or 3.9 R200 that will bolt into a GTS25T but the agro involves the half shaft adapters and ABS/non ABS differences .

Just for the record my Skyline is a 96 GTS25T without ABS and I assume has a viscous LSD which seems to work fine .

So I guess the go would be to try to find a non ABS S14 diff that had 5 bold half shaft adapters - and the same nose ear hole sizes .

Thoughts , cheers A .