i have a stock 1.6, 5 speed 91 civic si and my main concern for this car is to increase gas mileage. since the car runs at about 4000 rpm`s at 80mph, i figured there was a tranny mod or swap that could lower the rpm`s. i`m not concerned with performance since this car is a turd already.

what year and model cars have final drive trannys that are direct replacements for the 91 civic si transmission?

i suppose if i find a different tranny with a higher final drive then i`ll have an si tranny for sale also.

any advice is appreciated. thanks

 

try a hf 5th

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by collins1 &raquo;</TD></TR><TR><TD CLASS="quote">i have a stock 1.6, 5 speed 91 civic si and my main concern for this car is to increase gas mileage. since the car runs at about 4000 rpm`s at 80mph</TD></TR></TABLE> I drove from CFL to NC in June of 2006 and averaged 37mpg roughly with a SI transmission.

 

You can use ANY 1989-1991 transmission in your car without ANY modifications. And either the HF or DX/LX transmissions will give you lower freeway revs. Whether this will translate to better MPG is another matter, as the SI motor was really designed around those gears. You might try picking up a DX transmission, as the HF is probably so tall that it might actually hurt MPG. But either of these transmissions can be had for nothing. You could also do the HF fifth gear swap into your SI transmission. This would give you a fifth gear that is about the same as the DX fifth gear, but without the gearing penalty in gears 1-4. This will help acceleration around town. And city mileage might be better as well, since the motor won't be so 'overgeared' around town.

 

Edited by CRX Toad.

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