R33 Gts-t Diff Ratios

[teng]

Stock Gear ratio on R33 GTS-T is 4.111/4.363 (i dunno which one i have)

What if i change the ratio to 3.538?

I searched around and found that it will;

1. Reduce acceleration and torque

2. Increase fuel consumption

3. More gear change as it will hit the limiter faster (need to confirm)

4. Higher maximum speed (need to confirm)

Final Question, will it benefit the GTS-T to have a 3.538 final gear ratio?

Anything that is wrong please correct me.

Thx.

Edited September 18, 2009 by teng

[teng]

Was browsing other sites for information and i got this;

"With a shorter gear ratio (i.e. 4.111) the consumption will increase and cruising will become more 'noisy' due to the higher cruising revs, but in exchange more power and torque will 'transmit' to the wheels."

"Going down in ratio gearing can improve traction and widen the gears for high power applications (i.e. 3.5 ---> 3.3) This is generally NOT recommended for naturally aspirated or lightly modded vehicles. It can severaly slow down the accelleration. "

So with those statements, i guess 3.538 final gear ratio is best suited for turbo applications and i can get better fuel economy.

[mad082]

that is a pretty big jump in ratios.

the diff ratios are on the nissan ID plate. i can't remember where but somewhere it will say either 411 or 433 (or it might just be 41 and 43). if you get a pic i could tell you. if you have the 4.3 then i would only go to 4.11, if you have the 4.11 then i don't know if i go as tall as 3.5 if i was you.

you are right in saying that you will reduce acceleration (be like taking off in second gear instead of first). it will give you a higher theoretical top speed, however it may actually lower your top speed (will explain more about this in a second). however it won't make you need to change gears more often like you said. in some aspects it will, but won't in others. you will have a higher top speed in each gear, so when accelerating you will have to change gears less often. however if you drive around hilly areas you may be changing gears more often due to the lower torque. but that really depends on your gear selection to start with. also acceleration will be slower because at lower rpm you will be spending more time off boost. so if you are cruising along and put your foot down it will take longer for you to get into the peak section of the rev range. this can affect how often you have to change gears.

now more about the higher top speed. if you have plenty of power then your top speed will be higher with the lower diff ratio. however if you don't have that much power then your top speed will be lowered because the gearing is too tall for the engine to push. it is similar to if you are going up a steep hill in top gear at 60kmh. you may get to a certain speed where it can't push any more and you stay at that speed, but then if you drop down a gear you can go faster. the same goes with changing gear ratios.

fuel economy is a bit of a tough one to say how it will affect it. on the highway you may use more fuel or you may not. it just depends on how much it alters things. it may make it too tall to use 5th gear unless you are doing 140kmh or more. so you may end up using 4th gear and having it rev a touch higher than what it used to rev in 5th gear. or 5th gear may still be usable but you have to use a higher throttle percentage than the shorter gearing. for round town driving you will probably use a touch more fuel as you will have to use more throttle to launch without stalling etc. it really does depend on how much it changes things. as much as i like the RB motors, they aren't exactly a torque monster in the low rpm range, which is why nissan gave them such a short ratio to start with when compared to the big aussie sixes which run ratios around the low 3s. if you were to put 4.11's into a commodore or falcon then economy would go out the window because they are very tall geared to start with, and are designed to rev at under 2000rpm at 100kmh and have the torque to do so. to give you a better idea of this, an manual commodore v6 will do close to 110kmh in second gear at 5500rpm. a turbo skyline will do a similar speed in second gear, but with another 2000rpm. another thing to consider is that a vt commodore is making it's peak torque of 304nm at 3600nm, while a r33 only makes 294nm but at 4800nm. so it makes less torque and doesn't make it until not far from the redline on the bigger car. or to even more make the point, an au falcon makes 357nm at only 3000rpm.

as you said, going taller gearing will give you better traction. the example of trying to launch in second gear is a good example of this as well.

i really don't think you are going to get better fuel economy with the shorter gearing, especially with such a big jump. as i said, the rb motors really don't have enough torque to pull it off. they are designed to rev and will get the economy from using low throttle percentage. i think you would need to take into account what sort of engines they were talking about on the site you read the info in your second post from. if they were talking about big cube engines then you can't compare that to a small cube engine.

[teng]

mad082. Thanks for the long reply. Really explains everything. I checked the nameplate and it says RC41, so my diff ratio is 4.111.

The 3.538 diff ratio is from a ER33 RB25DE Automatic. It didn't have l.s.d in it as i can turn one of the driveshaft and hold the other one. On research, the pumpkin has option l.s.d which could be installed. I know the ratio cause i split the pumpkin and counted the gears. 46 Ring Gears and 13 Pinion Gears. Since i have a Spare pumpkin from the auto RB25DE, i wanted to install a l.s.d. and put it on my ECR33.

I recently acquired a Nismo 1.5way L.S.D for ECR33. According to the Nismo manual, it will fit the RB25DE Pumpkin casing and the only thing i had to change was the driveshaft which has 6bolts (3x2) and my ecr33 has 5 bolts. The driveshaft were included in the Nismo L.S.D. Package.

My car's power is now 250hp@flywheel, i don't know how much torque i have now but i will be putting in a HKS GT2530 (320hp) soon so i hope that will give me some added torque.

Since the pumpkin came from an Auto RB25DE (230NM@6400rpm) which has less torque than the stock ECR33 (294NM@4800rpm) so it should be ok, am i right? Rev it higher, i should get over 300NM of torque.

The only issue i have after reading your post was my 1st gear will be useless. Does that mean i start the car with 2nd gear?

Another is whether should i crack open my stock diff casing and install the 1.5way there or just use the RB25DE diff case.

Edited September 19, 2009 by teng

[blind_elk]

The only issue i have after reading your post was my 1st gear will be useless. Does that mean i start the car with 2nd gear?

You will definitely need 1st gear. There is little chance the car will start moving in 2nd gear with that change in final gearing.

It's all about leverage. Try levering a weight with a 4.1:1 mechanical advantage, then try it with only 3.5:1 .

[mad082]

mad082. Thanks for the long reply. Really explains everything. I checked the nameplate and it says RC41, so my diff ratio is 4.111.

The 3.538 diff ratio is from a ER33 RB25DE Automatic. It didn't have l.s.d in it as i can turn one of the driveshaft and hold the other one. On research, the pumpkin has option l.s.d which could be installed. I know the ratio cause i split the pumpkin and counted the gears. 46 Ring Gears and 13 Pinion Gears. Since i have a Spare pumpkin from the auto RB25DE, i wanted to install a l.s.d. and put it on my ECR33.

I recently acquired a Nismo 1.5way L.S.D for ECR33. According to the Nismo manual, it will fit the RB25DE Pumpkin casing and the only thing i had to change was the driveshaft which has 6bolts (3x2) and my ecr33 has 5 bolts. The driveshaft were included in the Nismo L.S.D. Package.

My car's power is now 250hp@flywheel, i don't know how much torque i have now but i will be putting in a HKS GT2530 (320hp) soon so i hope that will give me some added torque.

Since the pumpkin came from an Auto RB25DE (230NM@6400rpm) which has less torque than the stock ECR33 (294NM@4800rpm) so it should be ok, am i right? Rev it higher, i should get over 300NM of torque.

The only issue i have after reading your post was my 1st gear will be useless. Does that mean i start the car with 2nd gear?

Another is whether should i crack open my stock diff casing and install the 1.5way there or just use the RB25DE diff case.

ok, i think you missunderstood what i meant with all my examples of taking off in second gear. what i was meaning was that going to a taller diff ratio will mean that taking off in first gear may be like taking off in second gear with your current ratio. so it will be easier to stall, require more riding of the clutch and more throttle. it will make make taking off up hill harder, and put more stress on the clutch.

as far as both power and torque goes, your current setup is far from a torque monster, because you could be squeezing 300hp out of your setup and still have a higher max torque rpm than the sort of cars that run these gears stock. and even with the new turbo, you aren't really going to be gaining anything down low as most of the speed limits are at rpms where you aren't really on boost. and it is at those rpms where turbo cars are lacking in torque and big, slow aussies 6's and 8's will idle along easily without any problems at all.

i had around 285hp in my r33 with the stock turbo (was running 14psi) and i have also driven a mates r33 that had 330hp with a 3076 turbo. below 3000rpm neither car was as quick as any aussie 6 i have driven. i think that going to the auto gear ratios is going to ruin the highway drivability of the car as everytime you came to a hill you would have to drop back a gear. also it will make reverse gear faster too.

also, after doing a bit of research, the 3.5 gears are out of a natro rb25, which have more low down torque than a turbo. the turbo has more torque overall, but at low rpm the natro will pull away from a turbo without any problems. i used to have a 180sx with a turbo sr20, and the missus has a SSS pulsar with a natro sr20. out of slow corners from around 1500/2000rpm the pulsar would pull away like i was standing still. it wasn't until about 4000rpm that i would actually start making ground back. the difference between an natro and turbo rb25 will be less, but there will still be a big difference. also the fact that the auto can allow the engine to rev higher than what the gearbox is, so if it is going up hill and you put your foot down it can increase the engine speed without increasing the vehicle speed.

and i just did some calculation of your new rpms for the major speeds. they may be a little bit out, but will still give you the difference to what the new gears will be like

100kmh in 5th: currently approx 2500rpm. with 3.5 diff: approx 2200rpm

100kmh in 4th: currently approx 3400rpm, with 3.5 diff: approx 3000rpm

80kmh in 5th: currently approx 2000rpm, with 3.5 diff: approx 1750rpm

80kmh in 4th: currently approx 2700rpm, with 3.5 diff: approx 2350rpm

60kmh in 4th: currently approx 2000rpm, with 3.5 diff: approx 1700rpm

60kmh in 3rd: currently approx 2600rpm, with 3.5 diff: approx 2200rpm

and finally, with teh 3.5 diff being an open diff will make it terrible when you do happen to put the bigger turbo on. it will be whelspin city, especially in the wet. however you wouldn't have to worry too much about losing it in the wet because it would only be 1 wheel spinning, LOL

if i was you i would be putting the 1.5 way into your current housing.

[teng]

[quo

[teng]

[quote name='mad08

[teng]

if i was you i would be putting the 1.5 way into your current housing.

I just did that ............bit i'm gonna change the 3.538 gear housing with a 3.916 one when i get a change to got to the workshop. Since the L.S.D. is already in the 4.111

[teng]

[quo

[teng]

if i was you i would be putting the 1.5 way into your current housing.

I just did that ............bit i'm gonna change the 3.538 gear housing with a 3.916 one when i get a change to got to the workshop. Since the lSD

[teng]

if i was you i would be putting the 1.5 way into your current housing.

I just did that ............bit i'm gonna change the 3.538 gear housing with a 3.916 one when i get a change to got to the workshop. Since the L.S.D. is

[teng]

if i was you i would be putting the 1.5 way into your current housing.

I just did that ............bit i'm gonna change the 3.538 gear housing with a 3.916 one when i get a change to got to the workshop. Since the L.S.D. is already in the

[teng]

if i was you i would be putting the 1.5 way into your current housing.

I just did that ............bit i'm gonna change the 3.538 gear housing with a 3.916 one when i get a change to got to the wreckyard. It's about 100km from my home so i'm gonna do it much later. lol Since the L.S.D. is already in the 4.111 housing, don't wanna bother it anymore. I'll just keep the 3.916 (when i get it) and will change it when i get another chance to crack the pumpkin apart.

Thanks for all your help mad082 and blind_elk.

Now i know more about taller and shorter gear ratios

Edited September 20, 2009 by teng