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dx vs si tranny

Discussion in 'Civic and CRX - EF' started by goldwar, Nov 30, 2007.

  1. goldwar

    goldwar New Member

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    k i have a si tranny in my rex and it is on its last leg.
    i cant find a si tranny for a replacement.
    there is a used 1.5 tranny that the guys at jmd imports have but i was wondering
    what that will do for power. this is my autox car and my second gear redlines at about 30mph what does a dx second redline at? also is there any problems with mounting a
    jdm tranny in my usdm rex. oh hey i have i 89 si with a sohc zc......
     
  2. mikey bottles

    mikey bottles Prof. Bottles

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    all d series are interchangeable im pretty sure.. as far as gain/loss of power, or wether it will be the same i do not know.. i think i read on here before that the final drive is different between the si and dx trans
     
  3. norcalgsr

    norcalgsr Honda Master Technician

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    It will fit without a problem, but the gearing is longer on the dx trans so as far as acceleration it will not be as good as the Si trans.
     
  4. goldwar

    goldwar New Member

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    well does any one have a dx tanny cause i think i'd like to know how tall my second
    gear will be
     
  5. 93civicracer

    93civicracer Oh, I do a little here and there.

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    In my 93 civic dx second took me to around 40 if i'm not mistaken.
     
  6. goldwar

    goldwar New Member

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    sorry correction my first gear goes to 30 my second goes to 55 what does your guys second gear go to . well i have 2 crxs and one is a dx the other an si but the gearing is the same in both so i don't know if i have 2 dx trannys or 2 si trannys
     
  7. Jeef

    Jeef NO MA'AM Moderator VIP

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    I was going to say 2nd should top out at more than 30. Between the two in my old 91 sedan the dx tranny is longer, but the si did give better acceleration. If gas mileage is a concern if you do mostly highway driving then the dx is a little better. Personally I liked the si tranny better.
    Where are you located? I have an si tranny but I don't want to ship it.
     
  8. goldwar

    goldwar New Member

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    north idaho. this is just a track car so gas mileage is the least of my concerns i just think that i'm always seem to top out my second but dont have enough time to shift so a dx tranny might be nice to give me the little more time in second.
     
  9. Jeef

    Jeef NO MA'AM Moderator VIP

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    IF you want even longer gearing go with a 4spd std or an hf tranny. But between the si and the dx you will feel some difference but it wont be night and day IIRC.
     
  10. goldwar

    goldwar New Member

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    why does everybody say the gearing is shorter in an si. And i don't have the book on hand but i have read (Honda-acura engine performance) though a couple times and i swear it said that the si tranny had closer gears. well blanco i'm not trying to question your knowledge but i found this web site and used the tranny calc and it seems that the dx is longer? (CRX Math) Check it out and let me know what you think about my findings....thanks
     
  11. haao13

    haao13 New Member

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    :shrug:
     
  12. jlicrx

    jlicrx Senior Member

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    the Si has shorter gearing due to the final drive which is the differential gearing - the DX and Si transmissions have the exact same gear ratios for 1 thru 5 gears and internally use the same gear sets - the only difference is in the final drive gears which are 3.88 for the DX and 4.25 for the Si - what this means is that every gear gets multiplied by the final drive resulting in the Si being shorter in every gear - if you look at the calculator you posted, you will see in the upper left that it says select transmission DX/Si - they are together because they both have the same gears - you then need to select the final drive - the DX gearing is longer than the Si and the Si will top out rpm wise at a lower mph than the DX

    the gear ratios after multiplying by the final drive are: (higher number = shorter gear)

    DX
    1st - 12.64:1
    2nd - 7.36:1
    3rd - 4.89:1
    4th - 3.64:1
    5th - 2.997:1

    Si
    1st - 13.81:1
    2nd - 8.05:1
    3rd - 5.35:1
    4th - 3.98:1
    5th - 3.28:1
     
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