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Is it possible to mix and match gears in a 71C trans?


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I would like to make a close ratio gear box for autoxing.   Seems the secondary gears are cast onto the shaft?  Well a boy can dream about a race gear box.  

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Countershaft is cut from a solid chunk of steel, not cast.

But except for 5th, the answer is no.

I do see people selling complete gear sets in in Japan for those wanting to play with ratios.

 

Some trans, like Hewland aftermarket boxes, have individual gears on the countershaft, so ratios can be changed.

Real race car stuff, with real race car prices though. :(

 

But 5th can be changed, but I doubt you get into 5th on an autoX.

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eliteracingtransmissions.com in England makes a tidy dog ring 5sp using the standard main shaft

 

1st - 2.82

2nd - 1.97

3rd - 1.47

4th - 1.20

5th - 1.00

Edited by Bleach
fix spelling on the website name
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Well, that's better than PPG Austrailia wants for a set for my Toyota W58 trans, their close ratio dog set is over $8k !

 

But HPI in Japan make improved version of both the Nissan 5 & 6 speed trans, with better ratios, and stronger components for under $4k. And they still have syncros, so they are easier to live with on the street.

 

The 6-speed is originally from Nismo, as a replacement for the S15 Sylvia, that is known to be weak.

Nismo puts their own close ratio gears in it, that are stronger. Then HPI takes it and does other mods internally to bump the HP rating up to 450+, where the stock S15 trans would start failing at 250, besides having a really wide ratio spread.

I haven't read up on the 5-speed.

 

Shops in Japan then take them, cut off the SR20 flange, and weld all sorts of other engine flanges to them, including the L-series.

 

But for an auto-X car, it would probably be better to just find the closest ratio that Nissan put out in a production car, then build the engines torque curve to work with it.

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I don't know about the C, but if you take a mid ratio B from an '77-'78 620, '79-'84 810/Maxima, 280z or first year ('7only) 280zx with (3.321 first gear) and replace the main input gear and the counter drive gear with those from an '80-'83 280zx non turbo close ratio 5 speed, you can build a hybrid 5 speed with

 

 

MID RATIO

1st..... 3.321

2nd.... 2.077

3rd..... 1.308

4th..... 1.000

5th...... 0.864

 

CLOSE RATIO '80-'83 zx non turbo

1st..... 3.062

2nd.... 1.858

3rd..... 1.308

4th..... 1.000

5th...... 0.745

 

HYBRID CLOSE RATIO

1st..... 2.972

2nd.... 1.702

3rd..... 1.171

4th..... 1.000

5th...... 0.745

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