i want a higher final drive ratio in my car. being a 5spd 86 it has a stock 4.1 ratio.
i've seen 4.3's on mazdatrix and other less reputable websites. are there commonly available higher ratio ring and pinions? this isn't for the track so nothing beyond say 4.7, but are there 4.4's or 4.5's?

 

The highest commonly available ratio is the 4.30 ring an pinion. This is due to the longer pinion shaft used in the 2nd gen FC's. There are sometimes some 4.88 or 5.12's available used from some of the road race teams but that is getting to be few and far between. I know of one shop who might be making some available next year if they are successful in fabricating a new longer pinion from parts of a 1st gen and 2nd gen. But that right now is just a very big maybe. I don't know of any other shops currently offering new 4.88 or higher. Anyway, for street use the 4.30 should be more than enough because your gas mileage will sink into the sewers and you surely wouldn't be doing any street racing :-).

 

i understand the gas mileage issue, but with the added torque i should be able to use higher gears more often and therefore get better mileage. with the very tall 5th gear in the fc this is perfect.

 

Why not go with the 4.3 and swap to the somewhat lower GTUs 5th gear. Should be about the same. There is a 4.44:1, but apparently it's quite rare, and getting it and having it modified will probably cost over $2k.

 

the 4.3 and the higher 5th gear does lower your gas mileage.

after they've both been tuned up:

My 91 gets 24 mpg highway
My GTUs gets 22 mpg highway.

 

what im saying is that i know the 4.3 will give me lower mileage, but i should be able to drive around in the very tall 5th gear like all the time with that bit of added torque because the 5th gear ratio is like .697 or .711 or something outrageously low like that. i should be alright on level ground going 35 in 5th?

 

3500 rpm? yes.

35 mph.....no

 

The GTUs 5th is abut a .754 or something close to that, so the difference between a 4.3 and .754 and a 4.44 and a .711 won't be much at all, but it'll be cheaper.

FWIW I'm using SA gears now and I've got something like a .802 5th and the milage is still reasonable. I can still do about 23mpg on the highway cruising at something like 65mph over hilly roads. I like it because I can now pull up most of the hills in 5th, whereas before with the .6XX 5th I'd have to shift into 4th a lot more, which in itself hurts milage.

 

im pretty sure it won't lug above about 1800rpm and i think 35 will be around there

 

as long as i dont give it anymore than a hair of throttle which is fine for cruising around town