My rex (90 si) has become sort of a traveling car and I want to extend my 5th gear becase 80mph at 4000rpm isn't cutting it. I've posted this before and most would tell me not to mess with it, but I only want to drop it about 500rpm for every 10mph... so that would be 80mph at 3500 rpm. I just want to ask what needs to be done to do this... I know I need a HF tranny for parts, but does anyone know exactly how to do this? I took a trip from the coast of NC to Nashville, TN and averaged about 75-80mph and the car just sounded like it was screaming... I was SHOCKED with my gas milage though.... 43-45 miles per galon on 93 octane!! I think the turbo flows the air in easier for cruising so my mpg was either unaffected or it improved. Anyway, someone please inform me on this 5th gear swap... I know little about tranny's and have never taken one apart.

 

is the problem the screaming sound you hear or the gas mileage?

 

no no... I love the MPG. lol. Theoritically my MPG should improve with a longer gear, but the engine might have a little more load on it -500 rpms... that doesn't bother me, I just want a better cruising gear.

 

on my ls, 70-80 is also at 4k and it feels normal to me... i like it cuz with the turbo u can jus floor it not even downshift and still pull on people lol... i feel bad for my friend... b16 all motor goin 65-70 at like 4300 rpm... imagine going real far trying to go faster... like 6k rpm at 80 crusin...

 

http://crx.honda-perf.org/math/index.html

Si tranny w/ HF Final Drive = 2600rpm @ 80mph

 

Si final drive and HF 5th gear will get you around 3500 at 80 mph.