I have a 91 civic cx with a 5speed tranny and d15b2 engine. Do i still have to swap the si (hubs, knucles) to make the SI tranny compatable?

So basically when the fuel economy ratings for the 88-91 civic si are 28/33 and 31/35 for the dx.......is this difference mainly due to weight.....as highway gearing(5th gear appears to be the same from si as dx) is the same and that 2 mile per gallon difference is just from weight diff from cx to si.

ANd yes the gears from 1-4 are different which makes sense why the city mileage is worse in the SI as the CX tranny has taller gears than the SI from 1-4 but the same 5th. Therefore if I switched from a cx to SI tranny, I wouldnt really notice a difference in mileage as I always cruise in 5th even in the city...?? PLease can I get a confirmation on this,,,,I hope it is accurate.

 

not to be a dick.. but you coulda just searched for the number of splines or teeth the hubs.. axles.. anyway.. you don't have to swap out the hubs, but you will need the si axles, if you didn't alreaddy know that. And as far as 5th gear goes in the SI, its definitely less gas friendly if your doing over 60+ it drives the rpm's a little higher i'm pretty sure.. from what i remember in my DX anyway.... which i find annoying, but i still like the tranny.

edit: ..ohh search is down...

 

ok thanks, so I am assuming the hub change would be if I had the 4speed cx...but it makes sense that the axles are needed from the Si for the si tranny. Ok that sounds good, I am still a little confused on the internet information about the 5th gear being the same...but Ill figure it out..thanks

 

I want to say the only difference in the gearing on the dx vs si tranny's are the final drive gear, but I can't find the page I saw it on....

 

ya i found the page now with that...it is final drive....damn i though I could get away with 5th gear change...w/e .....thanks anyways