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robftw

Transmission ratios & acceleration

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My rear end is 3.545

Current transmission is

1 - 3.321

2 - 2.077

3 - 1.308

4 - 1.000

5 - 0.864

The trans im looking at is this

1 - 3.062

2 - 1.858

3 - 1.308

4 - 1.000

5 - 0.745

I feel when im going through gears the powerband drops off when going to 3rd, i want to remove this.

I also drop a lot of RPM while shifting. with this new transmission my 1st-2nd gear should have slightly slower acceleration but a higher speed in each gear with the benefit of being closer to each other it should be slightly "faster" correct?

Will swapping to the new transmission alleviate this problem?

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If your looking for more low down grunt on an NA car, changing the diff to a lower gear may mean you get the desires results. Have you tried how a 3.9 diff feals?

Edited by 24OZ

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I don't have access to one, but i do have a 4.11 on its way, its an LSD off the front of a 4x4 nissan patrol.

it wont be here for a few months though.

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Hmm I was checking some of your trans ratios the 1 and second do not match on any of my books. are these tranys from a ZX? usually the only thing different is the 5th gear. the 2+2 tranys have different ratios also but your ratios did not match my books, my books may be old and may not have all the different tranys. in the early days changing to a 77 5 speed cost a lot so many used the 200SX tranys for the 5 speeds at the cost of poor perfomance in the lower gears. Just a thought.

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I think, scratch that, I know you will get a better result with a diff swap to get your car "quicker" with alot less work and money. The gear ratios you list above are just going to move the issues you are having from one gear to another, don't you think?

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Those ratios match the '77-'79 Z/ZX and '81-83 ZX, respectively.

The close-ratio transmission is great, less drop from 2-3 shifts and a taller overdrive, for lower cruising rpm. I have the late ZX trans in my Z paired with a 3.9, and love the gearing. Before I swapped in the 3.9, the rear diff was a 3.54, and I still very much liked it.

Get the close-ratio trans, and if you decide you want even more tractive effort then install a higher ratio diff.

Ratios: http://zhome.com/ZCMnL/tech/GearRatios.html

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I put that trans (81-83) in both my Z and my 810. I loved the gearing with the stock 3.54 in my Z and with the 3.7 in my 810. Though the 810 was an L24E, with the 3.7, it pulled almost as hard as the Z w/3.54. On, and mayitin, you really need to get some newer books. :)

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Yep, the close ratio (81-83) is great! With my 3.36 differential, first and second are ludicrously tall, but with a 3.54 I bet it would be cool.

Oh, and 3.9 Differentials are generally difficult to fined in the U.S. except in an R200.

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I have an '82 tranny with a 3.7 and its a great combo. Walter, with that combination you have I'd imagine you are doing very low rps's on the highway. Out of curisouity what kind of mileage do you get if you keep it around 60-65 mph?

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post-22536-14150815595615_thumb.jpg

found a neat tool for this kind of thing, this new trans looks like the way to go.

Now for that 4.11 lsd...

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[ATTACH=CONFIG]46701[/ATTACH]

found a neat tool for this kind of thing, this new trans looks like the way to go.

Now for that 4.11 lsd...

I've seen a similar tool but it doesn't plot the numbers. Is that one available on the web?

There is something odd about your attached picture though. Maybe you didn't redraw after putting in new numbers. 3rd gear plots the same line but 4th gear doesn't even though the values are the same for 3rd and 4th, between the two transmissions.

Anyway, I wouldn't mind a link to the site if you have it.

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I have an '82 tranny with a 3.7 and its a great combo. Walter, with that combination you have I'd imagine you are doing very low rps's on the highway. Out of curisouity what kind of mileage do you get if you keep it around 60-65 mph?

Well I get about 25 mpg on the highway at the speeds that I normally drive ;)

As for the fuel mileage at 60mpg... I will have to get back to you on that...

With the L24 60 mph is about as slow as I can go in 5th. It seems like 80 mph is around 3K RPM, but I don't recall if I have ever gone that fast. :rolleyes:

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I've seen a similar tool but it doesn't plot the numbers. Is that one available on the web?

There is something odd about your attached picture though. Maybe you didn't redraw after putting in new numbers. 3rd gear plots the same line but 4th gear doesn't even though the values are the same for 3rd and 4th, between the two transmissions.

Anyway, I wouldn't mind a link to the site if you have it.

http://fatboyraceworks.com/gears/

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Strange, works for me, on different computers even.

I get this on all my browsers... hmm maybe im missing an addon.. does it use flashplayer? or something else

noscript is also disabled...

ratiopage.jpg

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Pretty sure it's not flash, but I'm no software expert. You must be missing some sort of driver/codec/application/???. It works on Explorer and Firefox on my work and home computers.

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I think it's Java. I was looking at making something similar for my differentials website. I have a calculator up and running, but in a non-graphical form. Having the graphics really helps to see that 2-3 shift gap, and the calculator that Leon suggested is really the best one I've seen.

FWIW, I once GAVE my friend a close ratio transmission after we went to the track together, and I just walked away from him after shifting to 3rd. He had a wide ratio box and his L18 with Mikunis just fell on its face when he hit 3rd because the rpms dropped too low. We both thought we would be battling it out on the track, but due to the gear ratios it became no contest at all and wasn't nearly as much fun.

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I think it's Java. I was looking at making something similar for my differentials website. I have a calculator up and running, but in a non-graphical form. Having the graphics really helps to see that 2-3 shift gap, and the calculator that Leon suggested is really the best one I've seen.

FWIW, I once GAVE my friend a close ratio transmission after we went to the track together, and I just walked away from him after shifting to 3rd. He had a wide ratio box and his L18 with Mikunis just fell on its face when he hit 3rd because the rpms dropped too low. We both thought we would be battling it out on the track, but due to the gear ratios it became no contest at all and wasn't nearly as much fun.

It was java, i forgot to reinstall it after i reformatted my machine.

Also since you are the diff. man here would it be smarter to get a 3.9 instead of the 4.11? i don't care much for highway speeds or gas mileage

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It's a personal choice, but the difference in rpm from the 3.9 to the 4.11 is like 150 rpm at 70 mph. Depends on what tire size you use, but it's not going to be night and day. I personally would go for the 4.11, and if you have an LSD 4.11 already, that's even better.

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It's a personal choice, but the difference in rpm from the 3.9 to the 4.11 is like 150 rpm at 70 mph. Depends on what tire size you use, but it's not going to be night and day. I personally would go for the 4.11, and if you have an LSD 4.11 already, that's even better.

It is an lsd. its actually the front diff from a patrol. Do you know where i can buy the transmission gear for the speedo? I don't know of any car that came with it from the factory in the rear end..

And i will be keeping my tires the same, i will probably be using a 235 60 R14 tire for daily driving, maybe a 235 50 R14 DOT drag tire.

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That might be a tough one then. I guess you'd have to find a used one. Zbarn might be a place to look, or put a parts wanted ad here and at hybridz, etc.

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