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Rb20 5spd Questions

Ashman
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Ashman Contributor

Ashman

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Posted (edited)

Greetings dudes, Ive just swung over from nissansilvia.com (cause i drive a silvia).

Now im looking at putting an Rb20det gearbox into my s13, I dont expect any of you to know anything about this conversion, but what i want to know from u guys is the following:

1) What are the gear ratios of the r32 gts/gtst 5spd??

I have found the following, can someone please confirm,

1- 3.321

2- 1.902

3- 1.308

4- 1

5- 0.759

2) What is the gearbox model, the s13 box is FS5W71C, and i have been told that the r32 rwd box is also FS5W71C (the 4wd box is FS5R30A), Is this correct?

3) Now i have also been told that the s13 Ca, s13 Sr and R32 Rb boxes are identical except for the bellhousings (and the bellhousings are interchangable (this has been confirmed for the Ca and Sr boxes!)) But i have also been told that the R32 box is 20mm shorter than the other 2 thus the tailshaft needs lengthening and the shifter needs modding. Is anyone able to measure up a box for me? I need to know overall length from bellhousing to output, length from where the bellhousing bolts onto the box, to output.And if possible the distances between the holes that bolt said bellhousing to said gearbox.

4) Whats an acceptable price to pay for an Rb20det 5spd?????

Any help will be greatly appreciated (Plus asking these kind of questions in the silvia forum didnt yield too many answers so i hope u guys can help!)

Edited by Ashman
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Cubes Grand Master

Cubes

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RB20DET box's seem to go for around $500. :O

20mm shorter.. I wouldn't think 20mm would cause a problem as the yoke slides in quite far. I doubt it would strip the yoke due to it being 20mm less BUT it may cause some other issue I am not aware of.

Either way.. I would probably try it if it were only 20mm, just be sure to have that tail shaft catcher in place as it wouldn't be too fun having the yoke break and the tail shaft trying to flip the car. >_<

Ashman Contributor

Ashman

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RB20DET box's seem to go for around $500. :O

20mm shorter.. I wouldn't think 20mm would cause a problem as the yoke slides in quite far. I doubt it would strip the yoke due to it being 20mm less BUT it may cause some other issue I am not aware of.

Either way.. I would probably try it if it were only 20mm, just be sure to have that tail shaft catcher in place as it wouldn't be too fun having the yoke break and the tail shaft trying to flip the car. >_<

im thinking maybe the 20mm (if there is actually 20mm difference) may actually be in the two different bellhousings, not the box itself, ie: the ca bell may be 20mm longer than the r32 bell and people are measuring overall lengths of the two boxes and coming up as 20mm difference. If this is the case there shouldnt be a prob cause im gonna put the ca bell on the rb thus removing the 20mm problem.

Ashman Contributor

Ashman

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Quite possible..

Got pics of the silvia box? I remember seeing a few and it did look as if the bell housing of the silvia was longer, but it can be deceiving. >_<

Are you sure ratio's are the same though.

No pics unfortunately, my box is still in the car. My extensive research says:

Ca18 5spd:

1) 3.321

2) 1.902

3) 1.308

4) 1

5) 0.838

Sr20 5spd (supposedly same ratios as rb20)

1- 3.321

2- 1.902

3- 1.308

4- 1

5- 0.759

now before u all say only 5th gear is differnet why even bother swapping boxes and all that sh#t. The reason for the swap is to drop highway revs. I have completely exhausted the changing diff ratio avenue, and the only option left is the box swap. currently does 3700rpm @ 110km/h with the ca18 box. Now i know someone will say well y not use the sr box if the rb and sr have the same gearing and the sr is confirmed to bolt up. Well that is certainly an option that i am considering but i am looking at the rb side of things purely for the cost side of things (sr boxes r around $650 +).

Edited by Ashman
T04GTR Grand Master

T04GTR

Posted
Posted

well. as far as im aware. they should be the same length. the ca gearbox has a differant extension housing im pretty sure.

sr/rb should be the same length.

what exacly do you want? they all have the same gears inside.

the only diferance is the sr/rb turbo boxes have twin synchros.

from those revs im asuming you have a ca diff ratio. ie 4.3.

all 5th ratios are the sam throughout the range of 71c gearboxes.

Ashman Contributor

Ashman

Posted
  • Author
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well. as far as im aware. they should be the same length. the ca gearbox has a differant extension housing im pretty sure.

sr/rb should be the same length.

what exacly do you want? they all have the same gears inside.

the only diferance is the sr/rb turbo boxes have twin synchros.

from those revs im asuming you have a ca diff ratio. ie 4.3.

all 5th ratios are the sam throughout the range of 71c gearboxes.

Note quite, the 5th in a ca box is 0.838, 5th in an sr/rb is 0.759. diff is currently a 4.1:1 from an sr20 silvia. I wanna drop highway revs down. And the ca seems to have a 2 piece bell and extension, whereas an rb has a 1 piece but it looks like they can be swapped.

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