R32 Rally Car Diff Enquiry

[Sanouske]

Long story short ive built an R32 GTS rally car. Its using the GTST brakes and hubs and currently has a 4.3 open ratio diff which i believe is from a 180sx as its an R180 with the small ears, 4 bolt rear cover and 3x2 bolt flanges. Firewall code suggests its meant to have a 4.1? If i recall correctly.

Anyways, im planning on keeping the engine the RB20DE, so i cant use the extra HP of a turbo setup to benefit the launches and out of corner speed requirements im having. But what i want to do is fit a taller ratio diff. Something ideally around 4.9 or even 5.1.

I need it to have LSD also. Welding it will not suffice.

Is there any suggestions for what to look out for to fit my requirements? There is so much misinformation out there its becoming harder to precisely work out whats the best combination of parts.

I was hoping to find the unicorn front r200 diff fitted in some navaras/pathfinders that ran the 5.1 ratio and pinch the parts to use in a shimmed vlsd r200 rear diff and use the 5x1 shafts and half shafts if needed. But not having much luck locating anything as yet. Ideally a clutch packed LSD would be best but im happy to shim the vlsd to accomodate what i need. Also plan to swap the rb20 gearbox to a z32 gearbox to assist a tiny bit with the wide gap between 2nd and 3rd. Affectively tightening that up a fraction. As down the straights, Its a snoozer in 3rd.

Very much appreciate any of your ideas and assistance. I have posted this same inquiry over at the siliva forum to generate some discussion. But alas no results as yet.

thanks
chris.

[ANT_32]

If it's a Na r32 diff it'll be an open r200 4.3 ratio.

You can swap a diff centre out of any r200. You just need to shim everything correctly.

Don't reckon you need a shorter diff because mine used to be Na and it's really not that bad.

[Sanouske]

My appolgies, i just went back through my photos and found some i took when i last had it out.

Ive got it ass about face. Whats currently installed is a 4.11.

Ive added some photos to assist with what i currently have. Along with a photo of the car the last event we ran.

[Duncan]

And 4.4 is the shortest in the r chassis anyway, although as you said you might be able to find something from a Nissan commercial. C34 stagea, r32 gts4 and I think r32 gtst auto all ran the short gears.

Its a bit harder if it is an r180 not r200 rear diff; there are plenty of mechanical LSD r200 centres you could chose from (all you need for the ratio is to use your existing crown wheel and pinion with the new centre and matching half shafts.

[Duncan]

BTW love the brown paint scheme, very authentic.

anyway, you can find shorter ratios from those suggestions above. For the centre I am not sure what those 3x2 bolt half shafts come in so count the splines as well. There should be many mechanical aftermarket options, kaaz are cheap

[GTSBoy]

Here's my #1 hot tip. Do not consider a "shimmed VLSD" to be anything other than a total waste of time. They are shit, total and utter shit. You would in fact be better off with a welded centre than using a shimmed viscous diff.

In fact, as it is clearly a dirt rally car, a welded diff would actually be bloody well perfect. I would do that instead of trying to get a good mechanical centre, and spend the extra coin somewhere else on the car.

As for what centres will fit the car....go looking on Silvia type forums for pretty much and Kaaz, Cusco, Nismo, etc etc mech 2 way diff. They will all do fine (unless f**ked out). The highest ratio gears generally available will be 4.375, and they are not that common, pretty much only being found in GTS4s. Oh, and it absolutely is an R200.

I would not stress about getting lower gearing if you can't find any unicorns. With a locked diff you will get bazzillionty times more drive out of corners anyway. You will need to get used to that.

[JZP]

The car in the background had Nisspares on to. Maybe talk to that driver, considering he's doing similar stuff too?

[GTRPSI]

And how are you finding it Rallying a NA GTS is it competitive or just for shits and giggles?

Ground clearance and weight not a issue?

[KiwiRS4T]

And how are you finding it Rallying a NA GTS is it competitive or just for shits and giggles?

Ground clearance and weight not a issue?

An SDU member (NZ club) is rallying and hill climbing an N/A GTS with some success (wins). Main key seems to be reliability rather than big power coupled with excellent driving. Will dig out some pics when I get a chance.

[KiwiRS4T]

Actually i lied - Shane's car is an RB20 n/a making 97 RWKW. With a roll cage it weighs 1160kg.

Here's a vid:

outside view:

The build thread (32 pages) http://www.skylinesdownunder.co.nz/forums/index.php?topic=52581.0

[warps]

In fact, as it is clearly a dirt rally car, a welded diff would actually be bloody well perfect. I would do that instead of trying to get a good mechanical centre, and spend the extra coin somewhere else on the car.

No it wont

There are 2 camps in the gravel fraternity. Those who love locked diffs on gravel, and those who hate them. Both camps are right (ie either it suits your driving style or it doesn't). all of the best club rally drivers I've known hate them and would never use one because of their unpredictability. I've run proper plate LSD's in several (FWD and RWD) gravel cars and a well set up LSD is perfect. Well worth the coin IMO - even for a low powered car.

Edited December 11, 2015 by warps

[GTRPSI]

I grew up in the Group B era, i was Rally driving from 18 till 23 on a club level in a Corolla and Datsun 1600.

I always preferred a single spinner on gravel, i could always get on the power earlier while maintaining the pull into a straight line after a turn faster.

Locked diff always had me sideways longer while powering out which meant i had to hold back longer.

Same under braking, a locked rear diff had me braking earlier with a slower mid corner speed due to the extra rear looseness caused by the locked diff.

[Sanouske]

BTW love the brown paint scheme, very authentic.

anyway, you can find shorter ratios from those suggestions above. For the centre I am not sure what those 3x2 bolt half shafts come in so count the splines as well. There should be many mechanical aftermarket options, kaaz are cheap

Thanks mate, eventually ill be repainting the car Bayside Blue with some other colour thrown in. In the end it will be stickered with sponsors and club even info.

I have seen some Kaaz centered diffs available but all get snapped up pretty quickly. Will keep on the hunt, thanks.

Here's my #1 hot tip. Do not consider a "shimmed VLSD" to be anything other than a total waste of time. They are shit, total and utter shit. You would in fact be better off with a welded centre than using a shimmed viscous diff.

In fact, as it is clearly a dirt rally car, a welded diff would actually be bloody well perfect. I would do that instead of trying to get a good mechanical centre, and spend the extra coin somewhere else on the car.

As for what centres will fit the car....go looking on Silvia type forums for pretty much and Kaaz, Cusco, Nismo, etc etc mech 2 way diff. They will all do fine (unless f**ked out). The highest ratio gears generally available will be 4.375, and they are not that common, pretty much only being found in GTS4s. Oh, and it absolutely is an R200.

I would not stress about getting lower gearing if you can't find any unicorns. With a locked diff you will get bazzillionty times more drive out of corners anyway. You will need to get used to that.

Ive been racing in an open, a welded diff and in clutch centered diff car and as commented below, having a properly shimmed clutch center is far best for my driving style. I agree shimming a VLSD isnt ideal, but its better then the open for starters until i work out what i want to use in the long term. It wont last forever but its a start. Lower gearing will help with the gearbox ratios as currently im stuck using 1st and mainly 2nd gear and only just touching 3rd in the long straights, but without the extra HP its a bit doughy. If i can shift the gearing field ill have better driveability.

The car in the background had Nisspares on to. Maybe talk to that driver, considering he's doing similar stuff too?

Hes using a clutch centered r200 with a 4.3 ratio. However hes also supporting a hotted up SR20det. So compensations can be made. I do have to touch base with him as he does have other diffs in the workshop which they were playing with during setup.

And how are you finding it Rallying a NA GTS is it competitive or just for shits and giggles?

Ground clearance and weight not a issue?

Suprisingly well. We wanted an s13 but i physically wouldnt fit. Im 6'4 so it wasnt going to work when all caged an kitted out. The R32 is tight, but managable. Engine reliability has been good. I rewired things and got the cooling system all sorted, along with air intake and so on. Apart from needing to fit a PS cooler mid year, its been solid all year. Gearbox is a bit meh, pops out of 2nd in very harsh conditions. But as mentioned i plan to swap the zed box into it. Ground clearance is good, ive eaten embankments and tyres which were flicked into the driving line by previous drivers, built a very solid sump guard. Sumps are quiet exposed underneath. I custom built the shocks using Stagea and 300zx Tein coilover tubes, lengthened to support inserts. The front inserts are from a mitsi colt and the rears a toyota camery. Springs are 300zx and aftermarket skyline, RS-R i think it was. We did break the cradle mid year, unknown to us before buying the car (street daily driver) it was already damaged and repaired. The repair broke. So i got a replacement cradle and gussetted the shit out of it.

As for being competitive. Very. Being this year was an R&D year for the car, before we invest too much time and effort into it. I came 3rd in class. Which is 2L Modified. 1st position was a hotted up rally spec FWD pulsar (not sure how but his point total was very close to ours). 2nd was my mate in his rally modified Datsun Stanza. With the 4K+ suspension job, and hot L20B. This engine just pulls and pulls. Super nimble on the dirt. And then us, in our relitively tame R32. So suprised is what we were. Certain tracks we where quicker then the above mentioned, and also some 4wd imprezas. Its holding its own.

With further R&D we should be pretty good. Ive got to upload the in car footage so one day ill link it in.

No it wont

There are 2 camps in the gravel fraternity. Those who love locked diffs on gravel, and those who hate them. Both camps are right (ie either it suits your driving style or it doesn't). all of the best club rally drivers I've known hate them and would never use one because of their unpredictability. I've run proper plate LSD's in several (FWD and RWD) gravel cars and a well set up LSD is perfect. Well worth the coin IMO - even for a low powered car.

Spot on. Ive raced in a welded diff car and while its improvement over open, the corners werent as tidy as they could have been. Proper LSD is the way to go and agreed, worth the money and time investing.

I grew up in the Group B era, i was Rally driving from 18 till 23 on a club level in a Corolla and Datsun 1600.

I always preferred a single spinner on gravel, i could always get on the power earlier while maintaining the pull into a straight line after a turn faster.

Locked diff always had me sideways longer while powering out which meant i had to hold back longer.

Same under braking, a locked rear diff had me braking earlier with a slower mid corner speed due to the extra rear looseness caused by the locked diff.

This is what we found so far with the open diff on this car. Power late into the corner to keep momentum up and power out early without sacrificing too much forward drive due to wheel spin, its all rather predictable. It is quiet easy to drive this car this way, but when the car starts to drift over the width of the road out of high speed corners or oversteer into sharp linking corners, the LSD would help keeping it a little more on task. Ive approached the corners more sedately to keep the car in coarse, but im sacrificing too much time in and out of them. Ive also ran a series of different wheel alignments to assist in keeping it where i need it. But im at its pinnicle where by i need more drive from the rear, via a well organised diff.

We ran locked cars also, the above mentioned stanza is a welded jobbie now and while its good. I feel hes loosing time catching the car into the corners and loosing time in the corner as it slides around. Being super light it doesnt have too much drift as the heavier cars do, but still a second here or there catching the car due to its inability to turn it properly, kept him off the 1st podium this year. IIRC the stanza was only a handfull of points behing the Pulsar. To which i dont know what its not in 2L modified FWD instead of 2L modified Open class.

Anyways people, thankyou so far for your comments. Appreciate them all. Will still accept any new info though.

Cheers

Chris.

[GTSBoy]

I'll never claim to be a rally expert. but I did grow up driving sideways on country roads. My open diff HG Kingswood drove alright, but a welded diff HQ that a mate had, which is otherwise really very much the same car suited me much better (for the sorts of "rallies" that we used to do, which mostly involved Lutheran youth groups and cheap port!). Likewise a welded diff 405 that my brother-in-law used to bash around. That places me in the welded diff camp I suppose. I don't mind the feeling it gives the car.

But if you want a mech diff, that's fine. There are plenty out there. I think the 3x2 bolt stub axles for the NA Skylines and S chassis cars are the same splines as the 5 bolt R chassis ones. So you should have lots of options.