dx vs si tranny

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goldwar

goldwar

New Member
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......
 
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
 
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.
 
well does any one have a dx tanny cause i think i'd like to know how tall my second
gear will be
 
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
 
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.
 
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.
 
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.
 
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
 
goldwar said:
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
Click to expand...
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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