A transmission question for any one who has or has thought of changing gear ratios.
 

Hi.
I do a lot of long distance driving and have noticed a significant gas mileage difference between RPMs at 3.5g and 4.5g, yet who really wants to slow down. I am also very aware of the difference 10-15 extra MPH can make over a 10+ hour trip. I don’t want to give up my every day/around town performance by changing the rear end and wondered if I could just put in a different ratio gear (for 6th gear). I spoke to two rebuilding shops and have been told there is no such part and it can’t be done. So I went home and began researching. I came across a site with specs comparing the RX-8 with the 5 speed and 6 speed transmissions. This is what I found.
Transmission
Feature Mazda RX-8 Std Power 5 Speed Mazda RX-8 Hi Power 6 Speed
Type 5 Speed manual / 6 Speed manual
Gear Ratio 1st -- 3.48 / 3.760
Gear Ratio 2nd -- 2.015 / 2.269
Gear Ratio 3rd -- 1.484 / 1.645
Gear Ratio 4th -- 1.000 / 1.187
Gear Ratio 5th -- 0.762 / 1.000
Gear Ratio 6th -- ------ / 0.843
Gear ratio Reverse -- 3.288 / 3.564
Final gear ratio -- 4.444 / 4.444
Drive wheels -- Rear / Rear

My questions are regarding 5th gear in the five-speed transmission and 6th gear in a six-speed transmission. Are the gears from the two transmissions that show different ratios, actually different sizes? Can they be swapped? Would swapping them give me the ability to lower my RPMs while still producing the same MPH in 6th gear of a six-speed transmission? And finally; if no,,, who might make what I am looking for?
Thank you.
Regards.

Angelo

toyota makes a camry

Think you would be better to just fit the 4.1 diff .

I doubt you will notice too much of a drop off around town - perhaps usethe next gear down .....

Yes; No. Peruse the RV world and look for a overdrive unit. Another alternative would be a custom built transmission.

I think that the 5 gear rx8s come with less hp. I know for a fact in Greece they have one with 197 hp and manual transmission (in U.S. they have the automatic). I think they call it rx8 cosmo and I think it has 5 gears and not 6.

just to cap this off, I continued researching this and found the two tansmissions do not to have interchangable parts. I will keep checking in on this and post any progress I make towards having something fabricated.

i would really go for the 4.10 rear gear from fluid motorsports.

it will make your car faster in a drag race to boot.