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Brabham

Diff Ratios

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Hi,

  What was the tallest ratio that Datsun put out in a stock R200 diff for a 240 or 260? My 2+2 is a 3.7 pretty sure but I want to go taller. I believe that 2 seater 260's had a 3.364 and I will at least go to this. Is there anything taller than this? What kind of top speed gain would I see by going from the 3.7 to the 3.364 and what is the tallest a stock L26 could turn over at about 5000 revs. Thanks for any info.

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I don't think you will gain much by installing a high ratio like a 3.3 in the zed, you might be going backwards. The engine will never reach peak rpm's. I would stick to the 3.7 or even better 3.9 ratio. Unless you have a V8 with 1000ftlb of torque don't bother. Or are you planning on going to the S.A. salt flats for a land speed record attempt in a zed...

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Nissan had the following ratios available for the R200 (some are very rare and hard to find these days but this is the complete list as I know it)

 

First is the ratio next is the teeth count on the crown/pinion

 

3.154 41/13 (special ratio hard to find)

3.364 37/11

3.545 39/11

3.700 37/10

3.900 39/10

4.111 37/9

4.375 35/8

4.625 37/8

4.875 39/9 (special ratio hard to find)

5.143 36/7 (special ratio hard to find)

 

The common ones (ie ones I have and can find here in NZ are)

3.364, 3.545 (from 300zx Z31 mainly), 3.700 (300zx Z31), 3.900 (depends Laural L20ET Auto's are a good source), 4.111 (R30/R31 Skylines)

 

I try to get from the later cars so I get the 12mm not 10mm versions, however if it is the ratio I want I don't care. I have a 3.700 and 3.900 that I might part with in the next few months however shipping to OZ is always going to kill any deal.

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Hi,

  Did 260's ever come with the 3.154 or was it an option or something? Cheers

That is why I said Special ie not standard like some of the others.

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Hi,

  Does anyone know where I could find the 3.154 or taller in Aus? What car did this come out in? Would like to find around a 3:1 or even 2.75 or 2.5. Thanks. :)

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Why do you need such a tall ratio? Are you building a land speed record breaking Zed? ???

You can take what NZeder has said as gospel - no other factory ratio's taller than 3.1 were made. 

 

If you’re so desperate for a taller than factory ratio, you could always get a CW&P made.

There are suitable machine shops in Australia that can do this for you.

 

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Yep I agree with Lurch why would you need a taller diff than 3.36? I actually have a 3.36 LSD sitting at home but I do plan on going to the Salt Lakes in SA in a couple of years and go for a Zed top speed. With this ration and engine combination I would be looking for more than 300klms maybe to 330 if I was extremely lucky. Can you explain why you would want to go that fast or faster? You certainly can't do it anywhere on the road or on any race track. Especially if you only have 6 cylinders as it simply wouldn't happen. Dimitri was dead right with his initial comments.

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hmmm.

 

i remember when i got my 4.4 LSd for my zed the guy had a 2:75 lsd in stock too. The place was called Adelaide Jap Parts they also have a website http://www.adelaidejap.com.au/ . now not sure if he still has it i bought mine about a year ago. but worth a try he may have some more stock.

 

Craig a 6 potter with a turbo will get to pretty good top speed. dont need a V8  ;D but to run a higher diff ratio that Brabham is after that 6 better have some decent turbo on it with decent amount of lag.

 

im thinking going 3.7 from 4.4. just feels that im doing too many gear changes in short period of time. but all my speedo gauges and  sensors are working quite well for a 4.4 with 16" rims so bit reluctant to change it now.

 

i just hope i can install my open wheeler 3.7 for a test. i think the tailshaft flange has a lip which i dont think is compatible on the original 260z diff. the 4.4 is from an import and the flange has a larger diameter lip than the stock one.

 

 

 

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Ha yeah RBZ I wasn't thinking Turbo. I put a 3.9 in my car and I must say the ration feels perfect to me. The 3.36 was high and held me back a bit on the track and was always driving around in a gear below normal. But I do want to make the Salt Flats one day. Got a few people keen to go over with me. The G-nose should help me get up there as well. Ahh one day.

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Nissan had the following ratios available for the R200 (some are very rare and hard to find these days but this is the complete list as I know it)

 

First is the ratio next is the teeth count on the crown/pinion

 

3.154 41/13 (special ratio hard to find)

3.364 37/11

3.545 39/11

3.700 37/10

3.900 39/10

4.111 37/9

4.375 35/8

4.625 37/8

4.875 39/9 (special ratio hard to find)

5.143 36/7 (special ratio hard to find)

 

The common ones (ie ones I have and can find here in NZ are)

3.364, 3.545 (from 300zx Z31 mainly), 3.700 (300zx Z31), 3.900 (depends Laural L20ET Auto's are a good source), 4.111 (R30/R31 Skylines)

 

I try to get from the later cars so I get the 12mm not 10mm versions, however if it is the ratio I want I don't care. I have a 3.700 and 3.900 that I might part with in the next few months however shipping to OZ is always going to kill any deal.

 

If you do decide to sell the 3.9, let me know, im keen fr one, but i only really want gears, I cant justify the $1000 odd dollars they want for them at parts places.

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I could imagine taking off from a set of lights with a 3.1 diff; while the engine is struggling at 2500 rpm in first, and while everyone else has accelerated away and left you alone, you will probably spend the next 15-20 seconds slowly gaining speed and reach around 60+kph then you go for second, another low rumble from the engine struggling to get more speed and so on. Then you get to the next set of lights...Might as well get a commodore...

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what is the tallest a stock L26 could turn over at about 5000 revs. Thanks for any info.

 

On flat ground in top gear?  Probably the 3.7 it came with!

 

haha, nice Zedman240

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Am going for top speed maybe salt flats. Hahahaha pretty funny quote Zedman. Yes I am just after top speed and the acceleration does not bother me too much. If I find a reasonably priced 3.1 or 2.75 then I will most likely buy it. Salt flats here we come... :P

 

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Ahh Brabham I don't think you are comprehending what people are trying to tell you. The thing you need to tell us is how much power does your car have and what does it rev to? I had a 3.36 diff in my car and I would do 200kmh or more at 4000rpm. My car rev's over 7,000 rpm that equates to a car capable of well over 300kmh, if and I say only if the car will rev over 6K in top gear.

How fast do you want to go? If the above is the case then why would you want a 3.1 or 2.75 diff??? Unless you are looking to go 400kmh. But I am guessing if your car is a normally aspirated 6 cyl then you don't have a hope in hell of getting anywhere near 300klm no matter what bloody diff you have.

Sorry to spoil the dream but I thought I might need to put a dose of reality into this thread.

For those who don't know there is an annual event at the SA Salt Flats where 100's of cars gather to see what top speed they can do complete with timing devises, wind guages etc. Massive event with some awesome cars.

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im with craig. if you want ot go real fast top speed wise (dont want to go all scientific and put all to sleep) you need some serious engine and serious aerodynamics. past certain speed power required to gain extra km/h doesnt increase linearly but exponentialy. (oops)

 

anyway to keep it simple an example

 

if u need 50hp to get to 100kmh than if linear you need 100hp to get to 200 without looking at aerodynamics change at different speed. in reality its more like you need 300+ hp to get to 200km/h due to air resistance.

if you car is designed like a brick ie xd- xf falcon. you prob need 400hp.

(these are just figures pulled out of the hat for matter of explaining how it works dont have time calculating it all out. )

 

now early zeds are not much better than that xd falcon unless the Gnose has been installed which reduces drag. even with that its not that aerodynamic. so overcome that a bit more you need serious HP but than again the laws of physics will still prevail inculding high speed stability and the cars structure holding together.

 

just look at buggati veyron. very aerodynamic and huge 1000HP engine max speed over 440km/h.

 

i remember years ago when one chap was obssesed with gear ratios thinking his VN commmodore V6 NA will do 7sec down the 400m if geared right. hmmm i wonder y some hiped up drag cars need big tyres big HP engine and extra light weight bodies with aerodynamic improvemnt to do those times. they should just copy this commodore guy. LOL.

 

anyway hope it i explained it bit better.

 

we all could be wrong maybe this zed is designed for salt lake max speed but hes keeping it a secret.

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I was going to say as well the power you need to push a car through the air at high speeds is enormous! I've seen pics of cars that are equivalent aerodynamically to a chest of drawers after a high speed run, return with the roof caved in from just from the force of air against it. Unless this car is only going to be driven on a salt flat it will be useless on the public road. I Lycra clad cyclist will be leaving you at the lights! The secret to high speed is to have gearing low enough to help the engine multiply the torque at the wheels, and making it easier at high speed to push it through the air. Plus all engines make most power higher up the rev range. With a too low diff ratio, you are going to run out of road before you reach 4th! Why do drag cars have 4.11-5.8's?

 

I just think you are wasting time looking for a ratio like that when you can find a great 3.9 LSD for good all round performance! (plenty on epray)

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Have taken all this on board. I am looking to get to 300Kmh, so that is not all that fast. Car is not finished yet still deciding on ratio. I have the 3.7 and this is pretty good for our tracks here in Aus I agree, although 4.1s and shorter have better acceleration I just feel you would be giving away too much on the top end. However all our tracks are acceleration and hence why people like these ratios. I am thinking about getting a mental L28 ET, so power should be enough. I know that power and top speed is an exponential ratio. Given the 260 2 seaters came with a 3.364 I think my goals are achievable yet expensive :(. So my offer on a tall diff still stands if anyone has one in Sydney. Hopefully since no-one wants one, they might be cheap :) If I can not find one, I will settle for the 3.364 or 3.1. Anyway cheers for the advice but it is something I want to try. I can always go back to old faithful 3.7 if need be, and I will keep it as I may need it. I just wish more of our circuits were like the old Monza, flat chat in top gear with about one or two serious high speed corners. 

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Makes a bit more sense now if you're going for an L28ET because they produce a lot of torque low in the rev range.  300km/h is still a very big target!

If you're going to one of the salt lakes mettings then maybe you could take a few different ratios and try different ratios each run.  I'd assume you have a fair bit of time to change the diff between each run?

 

Good luck with it  :)

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3.364 is still not really common, i am yet to see, hear, feel and or touch one in person and i have seen and touched a few odd things, no comments from the smart ass' please!

a 3.54 is easy and almost low enough for what you are after, otherwise 1100$ will get you a 3.3 or like from kameari, see other post benZ i think????

for the gearsets only.

or a g/box with very tall 5th

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Had a 3.545 in a car but sold it, wanted to keep it but alas it went with the car. Car was an auto - why do people put autos in sports cars aaarrggghhh. I have noticed that there are a lot of z people on here from Melb and Brisbane, but not many people here are from Sydney. Oh well at least there are three places here that do z parts so most are still obtainable- plus ebay and its damn paypal!

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