Tokyo-RX7

looking to get the most out of my top end on my rx7. It's a S4 NA and lightly modded. I already kno what im gonna do with the engine. Now all i need is some thoughts on the tranny/ gearing and differential. I've seen some threads on what people have but havent really heard about their top speed. Im looking to push past 140mph. So far i hit about 140mph and then thats it. I dont believe there is a limit on the car is there? I figure it is the gearing. I have seen the miata gearing swapped into the rx7 tranny. I kno there is plasses that sell gearing kits to change my gearing. So what can i expect out of my top speed with what gearing. What kinda setup do you guys have and what are you maxing out at?

rx7b13

stock 140 is where im at, but if you put 3.9's in your diff that will help on the top speed a little. i dont know much about swaping out gears in the tranny. but i do know that miata gears are closer together so i dont think that will help out on the topend any

fcdrifter13

5th gear fails

tekwiz99

there was a thread about how fast did their car goes, but got killed due to meaningless discussion at start.
so, i'm with the idea that 5th gear fails.

unW7WZ

140... You do realize about the innaccuracies of the stock speedo right??

Tokyo-RX7

ya i kno about that 5th gear on the NA. it's horrible, thats why i thought about using the gearing from a miata (claires setup) and then change the differential gearing. Has anyone had any success in pushing their NA rx7 passed 140mph. Im gonna build a new motor starting next month and lighten up the drivetrain some. I just have to figure out the gearing to land me into a higher top speed.

Tokyo-RX7

im sure the speedo is a little off...but is it really that bad? enlighten me

fcdrifter13

Past 100 its real bad. Mine is off at least 25mph(at least mine is that bad, need a new one.) I have seen it vary though sometimes like 10mph

Tokyo-RX7

bad as in im going slower or faster then what my speedo says. Why is it off by so much?

fcdrifter13

bad as your going slower

Tokyo-RX7

is there a fix for it to make the stock speedo accurate?

fcdrifter13

im not sure really.

Tokyo-RX7

ok...back to top speed...setups

fcdrifter13

You can either get more power you run a shorter rear gear, that way you get more accel in 5th instead of hitting a wall.

Tokyo-RX7

ya i would like to run the miata tranny gearing like Claires setup. Then get the 3.90 rear gearing, lighter drive shaft and lightened flywheel. Im trying to reduce the rotational mass to really get my car going. It would be nice to see what people are running to acheive a higher top speed.

rx7b13

one way you can fix your speedo is get a gps thats what im doing

Tokyo-RX7

im prolly gonna get a Gtech or something. Havent really looked into that yet. Has anyone found a good fix for the 5th gear?