FS5W71C on a 240SX

[bmoses]

Hi Datsun community,

 

I know this inquiry isn't exactly Datsun related, however there seems to be a lot of knowledge in this forum about transmissions.  I'm wanting to create a close ratio gearset with a tall first gear.  I've done some research and there appears to be these Nismo gearsets that apparently have existed with 2.9 first gears.  There's also 81-83 280Z's with this gear combination apparently.  My question is do all 'C series transmissions have interchangeable parts?  And how on earth does one go about finding these Nismo gearsets?  I can't seem to find them being sold anywhere.  If I sourced a 280Z transmission would I be able to swap those gears into my 'C trans?

 

Thanks guys

Ben

 

[Stupid_fast]

81-83 ZX boxes are FS5W71B.

 

According to Datzenmike the main/counter shafts do not interchange with the FS5W71C.

 

 

If you're looking for a close ratio gearset, see OSgiken, and there are others I can't remember the names right now.

 

NISMO gearset ?? I've never heard of anyone having one in 3 years messing with my datsun.   They exist, but extremely rare and probably extremely expensive. 

 

 

The FS5W71C 240sx transmission is           1st 3.321, 2nd 1.902, 3rd 1.308, 4th 1.0, 5th 0.765

The FS5W71B 81-83 280zx transmission is 1st 3.062, 2nd 1.858, 3rd 1.308, 4th 1.0, 5th 0.745

 

 

Due to how close the two gearing specs are, there is really no point in going the trouble to have a weaker transmission.

As far as 5-speeds go the 240sx box is a nicely setup box for pretty much any usage especially on a wide powerband KA.  

 

The only reason us Datsun nuts (at least, me ...) care about having the closer ratio ZX box VS the wider ratio (76-79) 280z box is because we're running under powered L series motors.  My hopped up motor with a mild race cam is barely putting out similar power as a stock KA.  

 

 

If you're looking for performance gains, you're looking in the wrong area.

[bmoses]

Hey Stupid_fast, thanks for the response.

 

I saw those Nismo gearsets outlined in some other posts on this forum.

 

Is it not just a swap of the tailshaft section on the '71 trannies?  Evidently not?  I'm aware that my FS5W71C is regarded fairly well in the community however what i'm looking for is a tall and close ratio gearbox because I run out of first gear too quick.  I need more speed and less torque.  I'm running a turboed KA (which becomes a freakin torque monster on boost) @ 11psi and probably somewhere around 300HP, maybe a touch under that.  I dyno'd 224HP @ 6psi, haven't dyno'd 11psi yet.  

 

Anyway, I appreciate your information.  It does sound like it'll be an effort in futility trying to to piece this together.  What I'm dreaming about is this

 

http://www.frsport.com/Nismo-32010-RRS50-6-Speed-Transmission-SR20DET-S13-S14-S15_p_26092.html

http://www.nismo.co.jp/en/products/competition/mission/silvia.html

 

(same thing from two different web sites)  Too bad it doesn't bolt up to a KA.  IF ONLY!!!

 

The ratios on this hybrid trans are (in case you didn't follow the links).

 

Transmission                            1st        2nd      3rd       4th       5th         6th

NISMO Reinforced Cross          2.9071 1.9888 1.5373 1.2179 1.00000 .8624

Genuine 6-speed (FS6R92A)   3.6264 2.2000 1.5412 1.2132 1.00000 .76743

Genuine 5-speed (FS5W71C ) 3.3214 1.9023 1.3084 1.0000   .8378    - 

 

this is an S15 trans, built with the ratios I'm looking for, 6 spds, and a few other mods to make it USDM swap friendly.  I just thought I would spend some time trying to see if I could recreate something close to this that would bolt up to my KA.

 

In any event.  I do appreciate any and all feedback from you or anyone else from your community.  I'm a long time Nissan SR20/KA24 builder of both FWD and RWD vehicles and have been involved in my community since the late 90's.  I won't take any information for granted.  

 

Thanks again

[datzenmike]

There is a way to get the following gear ratios using an easily available 620 late 280z or Maxima 5 speed with the 3.321 first gear ratio.

 

1st.... 2.972

2nd... 1.702

3rd.... 1.171

4th.... 1.000

5th.... 0.745 

 

Simply swap the main shaft drive and counter shaft driven gear sets. You want the 23/29 tooth matched set.

 

 

This is still a 31.5" long 71B transmission and easily half as strong as your 71C. I would never change the transmission ratios on a turbo car. It's way easier to lower the differential ratio.

 

The difference between a 3.321 first and a 2.972 is about 11.7% so to get that difference in a differential you want to drop from your 4.083 (S14) diff to something around 3.656.... hell anything around 3.70 would do. You do realize that it will take way longer to get your car revved up into the boost...

[Stupid_fast]

 

There is a way to get the following gear ratios using an easily available 620 late 280z or Maxima 5 speed with the 3.321 first gear ratio.

 

1st.... 2.972

2nd... 1.702

3rd.... 1.171

4th.... 1.000

5th.... 0.745 

 

Simply swap the main shaft drive and counter shaft driven gear sets. You want the 23/29 tooth matched set.

 

 

 

This is still a 31.5" long 71B transmission and easily half as strong as your 71C. I would never change the transmission ratios on a turbo car. It's way easier to lower the differential ratio.

 

The difference between a 3.321 first and a 2.972 is about 11.7% so to get that difference in a differential you want to drop from your 4.083 (S14) diff to something around 3.656.... hell anything around 3.70 would do. You do realize that it will take way longer to get your car revved up into the boost...

 

 

 

 

WHAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAT!!!

 

 

I want to build one.

 

 

I have a 280zx 1979 box with 3.321 1st gear ... does it require combining two gearboxes or you mean just swap around the shafts on one box?  huh.

 

 

 

Hey Stupid_fast, thanks for the response.

 

I saw those Nismo gearsets outlined in some other posts on this forum.

 

Is it not just a swap of the tailshaft section on the '71 trannies?  Evidently not?  I'm aware that my FS5W71C is regarded fairly well in the community however what i'm looking for is a tall and close ratio gearbox because I run out of first gear too quick.  I need more speed and less torque.  I'm running a turboed KA (which becomes a freakin torque monster on boost) @ 11psi and probably somewhere around 300HP, maybe a touch under that.  I dyno'd 224HP @ 6psi, haven't dyno'd 11psi yet.  

 

Anyway, I appreciate your information.  It does sound like it'll be an effort in futility trying to to piece this together.  What I'm dreaming about is this

 

http://www.frsport.com/Nismo-32010-RRS50-6-Speed-Transmission-SR20DET-S13-S14-S15_p_26092.html

http://www.nismo.co.jp/en/products/competition/mission/silvia.html

 

(same thing from two different web sites)  Too bad it doesn't bolt up to a KA.  IF ONLY!!!

 

The ratios on this hybrid trans are (in case you didn't follow the links).

 

Transmission                            1st        2nd      3rd       4th       5th         6th

NISMO Reinforced Cross          2.9071 1.9888 1.5373 1.2179 1.00000 .8624

Genuine 6-speed (FS6R92A)   3.6264 2.2000 1.5412 1.2132 1.00000 .76743

Genuine 5-speed (FS5W71C ) 3.3214 1.9023 1.3084 1.0000   .8378    - 

 

this is an S15 trans, built with the ratios I'm looking for, 6 spds, and a few other mods to make it USDM swap friendly.  I just thought I would spend some time trying to see if I could recreate something close to this that would bolt up to my KA.

 

In any event.  I do appreciate any and all feedback from you or anyone else from your community.  I'm a long time Nissan SR20/KA24 builder of both FWD and RWD vehicles and have been involved in my community since the late 90's.  I won't take any information for granted.  

 

Thanks again

 

 

You're running a turbo KA?  And you're looking into getting a $3000+ close ratio gear set? 

 

 

 

If your running out of first gear too quick ... replace the final drive ratio !!

 

Go down to a 3.70 or 3.54.  No need to change gearbox ratios, final drive will give you the effect you're looking for at a LOT lower cost and effort. 

[deweyharding]

Datzenmike can you explain more?

[datzenmike]

 

 

WHAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAT!!!

 

I want to build one.

 

I have a 280zx 1979 box with 3.321 1st gear ... does it require combining two gearboxes or you mean just swap around the shafts on one box?  huh.

If you have the 3.321 ratio first gear transmission usually found on the '77-'78 280z and first year '79 280zx, '77-'78 620 and the 810/Maxima you can make this...

 

1st.... 2.972

 

2nd... 1.702

 

3rd.... 1.171

 

4th.... 1.000

 

5th.... 0.745

 

Simply by replacing these two gears from an '81-'83 non turbo 280zx box. The top one is the Main Drive gear and it drives the lower Counter Drive gear. These two gears are different sizes and number of teeth so by replacing them with a set with a lower ratio you can lower all the gears.

 

 

This info was passed on to me by someone here but I forget who exactly. I can post the page he sent me showing the different gear sets. and why it works.

[deweyharding]

Ok thanks.

[bmoses]

Great info guys, thank you.

 

It seems to me that replacing these gears is equivalent to changing rear end gear ratios in the driveline, yes?  I say this because this ratio is AFTER the reduction gears on the input shaft and countershaft, correct?  I realize that if I only wanted to solve a short first gear problem then a rear end replacement is the easy way to go and I have in fact done that by replacing my 4.083 with an Infiniti J30 3.9 with VLSD. (thank god).  That helped a little bit, but what I realized is that the taller rear end, while enhancing my first gear experience, had a widening effect on the gap between all other gears.  I'm afraid that going with an even taller rear end will exacerbate this issue.  I'm trying to visualize in my head what a gap from 2.9 to 1.7 would be like.  I guess I'd just have to try it to find out.  What I think I want is a 2.9 first gear followed up by ~1.9 second gear.

 

Changing the diff is far easier than rebuilding a trans.  Although a trans rebuild is inevitable in my future.

 

Thanks again guys.

[datzenmike]

 

 

1st.... 2.972
2nd... 1.702.... percent change.... 25.4%
3rd.... 1.171.... percent change.... 54.3%
4th.... 1.000.... percent change....
5th.... 0.745

[deweyharding]

Mike I have a 4x4 box for an lSeries with the 3.3 first gear will this work for the mongrel box?