Differential Ratios
 

I know that there have been several threads on this but none of them seem to cover what I am seeking, unless I have missed it

The Nissan 32/33 diff in Harrisons is (as I recall) a 4.1:1. I notice that Warwick has on his 'site an 'upgrade' to a 3.7 ratio. Has anyone used this with T5 or similar? How complex is it to do?

Merv

Merv,
The R32 is 4.3:1 and from all the information I have the R33 is the same. If yours is a R32 the S13 Nissan Silvia diff(3.7:1) will fit and only need the drive shafts from your diff fitted to the new diff and will bolt straight in from the bottom, a reasonably easy job. The manual S14(viscous lsd) and the S15 (gear lsd) will fit in with some mods. The spline for the drive shaft on the S14 and S15 are different so an adaptor has to fitted between the drive shaft and axle. If it is a R33 the S14 and S15 diffs might be an easier option.
The back cover from your diff also needs to fitted on to the new diff.
I bought a S15 diff from Ebay. There are a couple on ebay right now and they both are from a seller on the northside of Brisbane.

Warren

I have a couple of thoughts on this
 

Merv and Sharon I am not sure about what you are going to use the car for but, A couple questions and answer might give you another way to go. You didn't say how much power the motor has and since you are looking a T5 I am guessing in the 375-400 hp range. Is there any way you can find out what the ratios are in the trans? There is nothing bad about using a 4.10 rearend if you match it with a over drive trans in the .80-.78 range with 15" wheels. You would also look for a trans with a 2.20- 2.50 first gear. This would be for the street. Maybe a 2.70 max. My 5spd has a 3.15 first gear and 3.31 ratio in the rearend. I never use first any more.
The other thing is going with a TKO 500 or 600 trans. They are cheaper than a T-56 trans which with the right ratio might be the best choice. The double over drive one. Either one of these trannys have multiple shifter locations which will make driving more comfortable on the road. If you abuse the car a little, over engineer the drivetrain if possible. This will save you money in the long run.
How much will it cost to have the gears swapping in the rearend? Compare that to a stronger trans for the car with an overdrive. Alot of the mustang guys have gone from 3.55 gears to 4.10 for better all around performance. Rick L.

Thanks Rich and Warren. I have the R 33 I believe - at least that was painted on top of it! I should check somehow. Are there visual differences? (If so then I would need the S14 or 15 diffs). Sounds like a specialist job however.

Merv

Warren, Nissan info says that the R33 is 4.1 ratio (not 4.3) - confused! Msaybe I should identify the part number on mine.

Merv

Merv,
The attached web site has R33 GTST specs which has the diff ratio at 4.3:1.

http://justskylines.com/skyline/know...ech_specs.aspx

Sambo thought his R33 was 4.1:1 and I was of the same opinion until I looked up a number of Skyline sites confirming 4.3:1. Now you have found a site that it is 4.1:1. The only sure way is to rotate the rear wheel one rotation and count the number of times the tailshaft rotates.

The physical difference between R32 diff and the R33 diff are the mounting points on the front of the diff. The R32 has small tabs on the front of the casing and no rubber bushes. The R33 has larger tabs with rubber bushes.

The S14 and S15 have the same front tabs as the R33, but I don't know about the number of splines on the drive shafts.

Warren

Either way, 4.1 and 4.3 are both less than ideal. You can import a new KAZ centre in your ratio of choice from Japan at great cost (around $1000) or fit the S15 helical centre and matching half shafts. I used to own an S15 and they hook up very nicely once fitted with a camber kit. :)

I spoke to Warwick last week and regarding diff ratios he told me to speak to the guys who fitted the 3.5 (or whatever) into Stiffy's Daytona... turns out he lucked upon that second hand.

Might be worth calling japanautos.com.au (with that eBay listing) to see if they have anything else. They're in Brisbane which is handy for you Merv.

Edit: the final drive ratio of the S15 diff is 3.692. http://nissans15.com/spec.htm

Thanks Warren. Mine has the rubber tabs so I guess it is an R33. So Final Drive is the diff ratio? I had the (mistaken) belief that Final Drive was also related to the top gear ratio?

I guess I will have make sure that the S14 and 15 are fully compatible with what i have now.

Merv

Thanks also Sambo!

Merv

Merv, this is also worth reading: S13 Open Differential to S15 Helical.

Spoke to these guys, they can get new centres but you need to supply gear sets, etc.
http://www.driftshop.com.au/diff.htm

More info:

R33 GTR = 4.1
R33 GTSt auto = 4.36
R33 GTSt manual = 4.1

Fantastic Sambo! Many thanks. I think I will be doing this - even if it means buying the necessary parts and putting them aside for when I have some time.

Merv

More info found on the Skylines Australia forum - ratios by vehicle models:

4.900 - C23 Serena SR20DE 4WD Auto

4.636 - C23 Serena SR20DE 4WD Manual, C23 CD20T 4WD

4.375 - R32 RB20DET 4WD, A31 Cerfiro RB20DET 4WD

4.363 - R34 RB25DE 4WD, R34 RB25DE Manual, R34 RB20E, R33 RB25DE 4WD, R33 RB25DET Auto, R33 RB25DE, R32 RB20DET, R32 RB20E,
C35 Laurel RB25DE 4WD Auto, C34 Laurel RB25DE 4WD Auto, C34 Laurel RB25DE Auto, C33 Laurel RB20DE Manual
A31 Cerfiro RB20DET, A31 Cerfiro RB20DE Manual, S13 CA18DET, S13 CA18DE, C23 Serena SR20DE 2WD, C23 Serena CD20T 2WD

4.111 - R34 RB25DET Auto, R33 RB25DET Manual, C35 Laurel RB25DET Auto, C35 Laurel RB20DE Auto, C34 Laurel RB25DET Auto, C34 Laurel RB20DE Auto,
S13 SR20DE (ABS),

4.083 - R34 RB25DE Auto, R33 RB20E, R32 RB20E (ABS), C33 Laurel RB20DE Auto, A31 Cerfiro RB20DE Auto,
S15 SR20DE, S14 SR20DET Manual, S14 SR20DE Manual, S13 SR20DET Manual, S13 SR20DE (ABS), S13 SR20DE

3.916 - S13 SR20DET Auto, S14 SR20DET Auto, S15 SR20DET Auto, A31 Cerfiro RB20E. 5 & 6 bolt

3.692 - S14 SR20DET ADM Manual, S15 SR20DET Manual. 5 & 6 bolt

3.583 - R33 RB25DE Auto, C33 Laurel RB20E Auto

* transmissions as stated, if not listed it means they are available in either Manual or Auto.

Forum Link

Merv,
Now that you have information overload, if you are to the next meeting come grab me I will give you names of two people that have already installed S15 diffs into their cars (4.6ltr quadcam fords) and one who has installed a 3.9:1 (5 ltr windsor).
Warwick, when he had his factory car had a 3.7:1 Silvia installed.
The S15's were installed into R32 frames, into a R33 it is easier.

I still check ebay to pick up a spare and over the last 12months the number of R200 diffs available have decreased, so if do see one grab it even if you aren't ready for it.

Warren

I'm running 3.91 in my CR. I reckon they work great with the 6 speed box. 3.7 might be better for a torque monster LS2 or LS3 motor but my little 5.7 likes the 3.9 gears.

The 6 speed has a tall first and second gear so they are both very usable with the short diff gears.

The 3.9 gears with the T56 2.66 first gear has you shifting 1st to 2nd at 70KMH @ 6000RPM. That's with 315/35/17 rear tyres which are a bit under 26" tall

Cruising @110 in 6th has you ticking over at a nice economical 1700RPM or 2500RPM in 5th ready for a quick getaway.

The same setup with a T5 sees you shifting to 2nd at about 55KMH @ 6000 RPM

Cruising @110 in 5th has you sitting on 2200RPM with the T5.

The 3.692 or 3.583 might be a better choice with the T5.

Cheers

Warren, do you have any more info on the S15-R33 conversion? Eg, diff centre, half shafts, what else... rear diff housing cover?

Thanks

This is very helpful guys - any info that makes it easier to get the RIGHT diff and install it is greatly appreciated.

I had to smile on the 'site above when the writer said he hit the tight bolts with a 'rubber mullet' - S13 Open Differential to S15 Helical

I need one of those ...

More questions
 

Paul

I also have considered the change of centre and I am interested in the pros and cons. Why do you think the 4.1 and 4.3 are not ideal?

I am running a stock Mustang 302 and T5 with 0.68 top ratio. The R32 rear has a 4.3 ratio - I did an approximate check some while ago. The engine runs out of puff around 5500 rpm (either that or I do).

What would be the benefit in running the 4.1 or even 3.7 rear gears? I can see that economy might be better but that really is not the purpose!! I suppose dropping the rpm at 110km/h down from 2800(ish) might be good for long term reliability. I can imagine that I wouldn't be changing gears as often but would there be any overall performance benefit?

If I add some grunt to the power plant, I can almost see that the change in the diff might be useful, but with the stock 302, I am not so sure.

Cheers

Geof

Sambo.

With the rear cover from the R33 attached to the S15 diff it should fit straight into the cradle. On the R32 they had to make metal bushes to replace the rubber bushes as the R32 does not have rubber bushes.
Once in the cradle you will see that the snout of the diff sticks out about 20mm further than the R33 diff due to the position of the speed sensor. If your tailshsft is not yet made no problem as you make it to suit, if it is already made there should be enough freeplay to slide the yoke further into the gearbox(this what they did when the S15 diffs were fitted into the other cobras).
When they tried to swap the drive shafts from the R32 diff to the S15 they found the S15 drive shafts had 1 more spline than the R32 had.
Two ways to fix this are 1. Get axles from a SX200/S15/S14 which should be about the same length as the R33. The R32 conversion didn't use this method due the potential cost of the axles. They went the second way and made an adaptor that went between the S15 drive shaft and R32 axle. There was enough movement in the CV's to fit a 8mm spacer between. This might not be issue if the R33 has the same number of splines on the drive as the S15 has.
Both the cobras that had this conversion were 4.6ltr quad cam fords, one with a T56 and the other with a T45. The outcome was the same, quiter at highway speed, easier to maintain highway speeds , better fuel ecomony and able to us first gear for more effectively.

If you are going to do this mod replace the rubber bushes with metal bushes. Under hard acceleration the rubber ones can be damaged.

Warren

Warren,

You mentioned: "You can import a new KAZ centre in your ratio of choice from Japan at great cost (around $1000)". What is a KAZ centre and - despite cost would it be easy to install?

Merv

Got 'em. http://www.efihardware.com/products/...-differentials

Merv