Diff Swap For Rb30det?

[psi]

Has anybody swaped to a higher diff ratio to make use of the extra torque?

My R33 revs faily well on the hi-way, and before I add the new engine, I have been thinking about putting taller diff gears in it. something like 3.7:1

Also, with the extra torque and higher gears, i think it would get better fuel mileage on cruise...

what nissan runs a ratio like that, and can we pinch the speedo drive?

[bubba]

I'm running 3.9:1, not as brutal as my old stock 4.36s but still very nice and I have gained some speed back in each gear (as I don't rev the 30 as hard).

I also have a 25 box, used the Navara sender for the conversion and kept the 17T cog on there which seems pretty damn close.. speedo reads 7kmh high.

[Mr Jollwah]

Either that or try one of those 6sp truck boxes out of a commodore and a 4.3 auto diff?

[Dale FZ1]

You could try swapping in a Z32 spec diff, but why bother? You're then reducing the torque multiplication at any road speed in any gear, and undoing the purposes of building a bigger engine with more torque.

3.9 gears would probably make it a touch less busy and may achieve fuel consumption improvement but you'd never recoup the cost in terms of fuel savings. I'd only do it if that made the car feel how you want it to.

[Roy]

Surely the trad off is with the additional torque of the RB30 that you can spread the torque curve over a wider road speed range by dropping the diff ratio, which also means less time lost on gearshifts and also helps traction in a rwd car.

[Dale FZ1]

I think it depends on the intended use of the car. Agreed that putting in a numerically higher ratio will equate to a wider road speed range, but with 4.1 ratio it's still geared to at least 250km/h in 5th. Who wants to go faster than that?

Retaining stock diff ratio with the extra grunt of the 30DET should provide fewer gear changes but may give rise to more frequent traction issues when driven in anger.

I do think it's a matter of preference, and I'm not considering a gearing change for my setup. Aaron seemed to think his 2.5 is a touch busy on the highway, so I'm interested to hear experiences after making changes. Probably a good idea to do the engine first and diff later for a definitive answer. From memory Cubes tried it long ago.

[CEF11E]

I was also thinking of doing the swap but have twice decided to give it a miss.

my issues are

1. boost comes on to hard and fast and i wanted to bring on power more progressivly. and the solution is a more progressive turbo, better boost control and better tyres

2. fuel economy as i do a lot of 100km/h commuting. solution to this is to change the afr lo make it much leaner at cruise at 100.

both of these will work but so will changing the diff ratio.

I am going to get my hands on 3.2:1 and take the car to the salt flats one day. but for the road the 4:3 is ideal

[WHITER33GTS-T]

stolen from another forum , just incase someone is searcing like i was ::::

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.

If anyone can add to this list, either if its ratio or cars that we can find the diffs in.

http://www.skylinesaustralia.com/forums/Di...37#entry4337237

Just copied this from the thread I started a while ago. I want to do the same thing but im running a 3 speed C4 auto

Edited December 28, 2008 by WHITER33GTS-T

[psi]

The beauty of building a modern boosted car is that you can usually get a 'best of both worlds' approach happening. Sure I love horsepower, and yes, like everybody else, I dont want to be mindlessly pouring cash into the fuel tank..

So, If the RB30det produces 50~100% (give or take) more torque, Then I think (if it was a factory option) it would have been given taller gears to spead the torque curve and not have rev the poor thing to hard.

The car sees LOTS of skid days. LOTS! I am usually just nudging the 7800 limiter. No, not bouncing! I am not wanting to cain the daylights out of an engine that will happily supply the torque required (to spin the wheels at the speed I am wanting) at much lower revs..

So, by the info above, I should be able to track bown a skyline with the right gears and steal the speedo sender while I'm there.

On this note, I think I should be able to retain my best of both worlds concept!

Thanks

[WHITER33GTS-T]

I want to have something I can swap over from street use to the drags.

I think this would be sweet for the streets, But who has one they want to sell??

3.583 - R33 RB25DE Auto, C33 Laurel RB20E Auto

[bubba]

I wouldn't want any less than 3.9s on the street.. The main motivation for me was to get some speed back in each gear as I only rev to 6800rpm as opposed to 7500rpm with the RB20, a side benefit was being less hectic in the cockpit..

Who knows.. maybe I'll want my 4.3s back with the bigger turbo..

[WHITER33GTS-T]

Top gear in my auto is the same ratio as 4th gear in a 5speed. So I want something to drop the revs down quite a bit. I want to be able to go on a cruise and not have to stop at every servo on the way.

Had anyone changed the ratio???

I will have a rev limit of about 8200

[psi]

  WHITER33GTS-T said:

Top gear in my auto is the same ratio as 4th gear in a 5speed. So I want something to drop the revs down quite a bit. I want to be able to go on a cruise and not have to stop at every servo on the way.

Had anyone changed the ratio???

I will have a rev limit of about 8200

U and I r thinking the same way... I could use a higher gear when I'm skidding, but that will not help me when i'm cruising. and with all that extra torque, I cant see why i will need the lower diff ratio. And if I'm gonna bother with a ratio change, I'll also get a Kaaz LSD for it and grab the sender for the speedo.. I am actually surprised nobody has done this yet!

[MBS206]

  WHITER33GTS-T said:

Top gear in my auto is the same ratio as 4th gear in a 5speed. So I want something to drop the revs down quite a bit. I want to be able to go on a cruise and not have to stop at every servo on the way.

Had anyone changed the ratio???

I will have a rev limit of about 8200

So you're saying your 4th gear (Top gear) in your auto, is a 1:1 gear?

As 4th in the manuals is direct 1:1...

If this is the case, you should already have lower then the 4.3:1 ratios.

Also, from all my research, some of those numbers in the above table thing posted, are slightly wrong.

Also, I believe it was Cubes who stuck some 3.9s into his RB30DET, and found it slower as it took longer to wind on boost. I believe he's now back on 4.363:1...

You can do a search and find a very good thread with people who have actually done this, and I believe all of them have reverted back to stock diffs.

Edited January 2, 2009 by MBS206

[bubba]

Aren't auto 33's already around the 3.9 range? manual 33's are ~4.1:1 and autos are generally taller.. my gears came out of an auto S13. If it helps at all, my understanding of the difference between 32/S13 and 33 diffs is that the 33's have larger diameter crown wheel bolts.

3.9's with my setup didn't make it noticably slower (probably because my current turbo is waaay undersize), it made it a lot more streetable though!

[MBS206]

  bubba said:

Aren't auto 33's already around the 3.9 range? manual 33's are ~4.1:1 and autos are generally taller.. my gears came out of an auto S13. If it helps at all, my understanding of the difference between 32/S13 and 33 diffs is that the 33's have larger diameter crown wheel bolts.

3.9's with my setup didn't make it noticably slower (probably because my current turbo is waaay undersize), it made it a lot more streetable though!

R33 manuals run a 4.363:1 final drive.

I think it becomes "slower" if you're running a larger turbo, as if you punch it at 2000RPM, it say might take an extra second to get into your boost range... Hence, you're slower to get moving.

[bubba]

I thought R33 manuals had taller ratios than R32 GTSt's, mine was stock 4.363:1..

[MBS206]

  bubba said:

I thought R33 manuals had taller ratios than R32 GTSt's, mine was stock 4.363:1..

From what I've seen, R33 VS R32 manual, = same diff ratio.

This is from multiplewebsites I've read this...

Also, if you're revving an R33 manual to 6500RPM, and want to get it out to that same speed as what you'd normally be at at 7000RPM, you want a 4.1 diff.

[WHITER33GTS-T]

I wont be racing mine with the taller diff in it. Will just be for cruising around

Edited January 2, 2009 by WHITER33GTS-T

[WHITER33GTS-T]

  MBS206 said:

So you're saying your 4th gear (Top gear) in your auto, is a 1:1 gear?

As 4th in the manuals is direct 1:1...

If this is the case, you should already have lower then the 4.3:1 ratios.

Also, from all my research, some of those numbers in the above table thing posted, are slightly wrong.

Also, I believe it was Cubes who stuck some 3.9s into his RB30DET, and found it slower as it took longer to wind on boost. I believe he's now back on 4.363:1...

You can do a search and find a very good thread with people who have actually done this, and I believe all of them have reverted back to stock diffs.

My car was originally manual bit I changed to auto (C4) when i built the new 25/30