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  1. #1
    craig8585 is offline I'm so cool, I have my own fan thread :p
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    The ultimate gearbox thread!

    Gearbox failure is relatively common and the information about it seems to be scattered all over the forum, so here it is, all condensed into one thread. Thanks to _Wing_ for suggesting the idea.


    The options are..


    Replace 6-speed box

    Convert to S14 5-speed box

    Uprated gear sets for the above boxes

    Convert to Z32 box

    Convert to RB25 box

    Convert to other, very expensive options (HKS etc)



    Please keep all information and advice here FACTUAL, preferably from personal experience. None of the 'I've heard this', or 'my mate said that'.

    Links to websites offering parts and services on this topic are welcome, along with links to other threads but no business plugs. Keep that in the traders section.



    Related links..

    Changing oil in a SR20 gearbox
    S15 gearbox diagram
    S15 to S14 gearbox conversion
    Cryogenically freezing gearbox internals
    Z32 and RB25 conversion chat



    Companies/services

    PAR-Engineering - uprated gear sets
    AO-PS - gearbox conversions
    S-Body Automotive - Garage services in UK


    ^ - Additional recommendations will be added.

  2. #2
    craig8585 is offline I'm so cool, I have my own fan thread :p
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    I'll get the ball rolling.

    S15 gearboxes always have had a reputation of being weak, but they are no weaker than a S14 5 speed box. S14 owners generally accept it when a gearbox fails as a replacement is only 150 or so, but 6-speed boxes are 3-4 times the cost.

    I would never be satisfied with a 5-speed box in my car after using a 6-speed for so long, but if you run serious power then a conversion or uprated gearset will be the only option available..

  3. #3
    DeanS15's Avatar
    DeanS15 is offline My car is so clean you could eat off it.
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    is it also worth mentioning that the 6spd box may commonly suffer from a noisy input shaft? some people (myself included) think/thought thier box was on its way out when they start to hear a whine or a feint grind when off the clutch pedal that dissappears with the clutch pressed. this is a noisy input shaft (not clutch thrust bearing - which would be noisy with the clutch pressed instead). this is probably due to bearing wear, but it's by no means the end of the box, mine has gone on for almost 2 years problem free despite having this noise.......

  4. #4
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    Amazing Guide - http://forums.nicoclub.com/rb25-tran...s-t226812.html

    This shows how you mate a RB25 to a Z32 Rear Gearbox Case meaning you down need to cut any of the shifter hole as you would do with just a RB25 conversion
    This has been my bedtime reading the last few nights

  5. #5
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    Having just read the RB25/Z32 conversion thread (linked above), I can see why it's a safe upgrade, but I'm presuming the gear ratios are very different and will effect the drivability of the S15.

    I too am a fan of the 6speed box and wouldn't want to loose it. Are there no 6speed alternatives? R34?

  6. #6
    craig8585 is offline I'm so cool, I have my own fan thread :p
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    I think the only 6-speed solution is an uprated gear set in the S15 box

  7. #7
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    A complete reinforced nismo gearbox for the bargain price of 3500, plus shipping, duty and tax.

    http://www.rhdjapan.com/nismo-silvia...ansmission-set

  8. #8
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    If you but a uprated gear set in a S15 box you will waste your money and IT WILL blow again! and I have been advised this by Polo from S-body Automotive this inc gear sets from the likes of PPG etc

    The Z32 and RB25 gearbox's are the same apart from input shaft and out lengths the gears and internals are the same, main reason I am doing a z32 rb25 box is so I have a perfect shift alinement with out needing to butcher the shifter space already in the s15 if I was just to put a RB25 box in, as for affecting the drivability I cant see how it will apart from changing the fact it will be a 5 speed instead of 6, its will just take some getting used to for not going for 6th gear lol
    IF (and i mean if considering one of the guys I know down 2 seasons on the bdc on a rb25 stock box till it failed) the gearbox does fail you can always put a gearset in that and it will be 10x's what a S15 box with a gearset would be reliability wise

    If anyone has doubts or questions : S-Body Automotive
    Last edited by AllanOrr; 07-01-2011 at 01:05.

  9. #9
    craig8585 is offline I'm so cool, I have my own fan thread :p
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    Quote Originally Posted by AllanOrr View Post
    If you but a uprated gear set in a S15 box you will waste your money and IT WILL blow again! and I have been advised this by Polo from S-body Automotive this inc gear sets from the likes of PPG etc
    I'd like to know why he has said this. People on SXOC are running OS Giken gearsets with silly power without problems. All of the failings I have heard of on these boxes are either shafts snapping or circlip failure which would surely be ironed out by a gearset?

  10. #10
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    Has anyone ever investigated fitting a 5 speed box from a JDM S15 Silvia spec S (SR20DE engine model)? Assuming the internal strength is the same as the s14 K's gearbox (maybe someone knows?); you'd assume it would be a straight forward swap without some of the adaptations required for the s14 K's conversion. I'll see if I can find out from some locals.
    What do you call a Rx7 with reliability, decent build quality and a better exhaust note? - a specR S15!

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