Can i swap out my stock 5 speed for a newer si 6 speed?

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swervininacivic

New Member
I have a 2002 Honda civic ex coupe 5 speed manual and I want that extra gear to increase my highway mileage since it usually runs at about 3k to 4k rpm in 5th gear at 65-75 mph. Would a 2006 Honda civic si 6 speed fit properly with minimal modifications onto my 1.7l I4?
 
No. Totally different engine/transmission mate interfaces. You could make an adapter plate and bolt it up, but you'd have to bridge the clutch gap and then fabricate transmission side mounts too, plus possibly run custom axles if they don't match up in length and hub configuration to your stock dimensions.

If you're willing to dig into your transmission, you could look into swapping out the 5th gear set for something taller or change out the ring gear (final drive) on your differential. I don't know offhand what's compatible with that transmission though.
 
I'm pretty sure the D series (you have this) and K series spin in opposite directions too. This would make the swap impossible.
 
Also, if the Si's 6th gear is anything like 6th gear in my RSX, it's not really a good high mpg cruising gear anyway. Too short. I'm pushing 4k RPMs cruising at 75 mph...
 
Yeah the SI is about the same. In 6th gear on the highway, I'm doing about 3k at 70. There's just more gears in between. Works fantastic for climbing hills and cornering though.
 
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