Hey all! I picked up a '97 NA Miata, and I'm trying to sort out what gear set I want to swap to. The car is on 12 psi, currently makes 240whp. It has a Ford 7.5 rear end, currently with 4.10s in it. With the torque this car makes, I don't see any reason to run around at 4,000 rpm at freeway speeds, as well as first through third gears being practically unusable. So, I'm going to step down the gear ratio, but I'm unsure exactly what I want to run. I'm in between a 3.73 and probably a 3.55. I've researched and seen people saying that under 18 psi you want a 3.73, but I'm not sure that a 3.73 will drop my freeway rpm all that much, and would give me a little more headroom for more power later. Conversely, I don't want to go too long of a gear and put too much stress on the motor trying haul around too long of a gear. I just don't want to do the one and then wish I went the other way. What are your thoughts? I'm all ears, thank you!

 

240whp
180torque

What's wrong with the 4.10? Can't use the first 3 gears? Why not? Put a better tire on it, i hooked with a 195 tire, a little less HP and 4.10 gears.

 

First - is this is a street car or race car?
Second - is the engine built? Do you plan to run more in the future?
Third - is it on the stock 5 speed or 6 speed?

 

 

Not enough smileys need moar

 

 

You aren't making enough horsepower for the 355 gears. use the 373.

 

Are you running Walmart MayPop tires or something?

I wasn't aware that psi was a direct correlation to rear end gearing.... unless you're talking about tire pressure?

With how little power you're making, i'd do like... a 3.9. Maybe a 3.73 if you're feeling especially froggy.


Sincerely,

Someone who makes more power than you yet manages to dead hook 1st, 2nd, and 3rd with a 6spd and a 4.10.

 

This forum is spicy, I like that
Sorry about that, I had a feeling missed a couple of pieces of information.
-The car is a street car that may see some track days, but primarily a street toy.
-It's a 5 speed trans.
-While I'm not under the impression that the car is terribly fast, what I meant with the torque comment is that it's got enough bottom end that a little less gear isn't going to make it call on it's face. But I hate driving around at 4,000 rpm on the freeway at ~75mph. Also, I live in Las Vegas, and the streets are fairly greasy (my c6 z06 goes sideways at WOT till 150mph, even my bolt-on 135i spins through the top of third)
-At this point, the car is on a stock block. Whenever it decides to check out, I'll build it bigger and better.

 

I'd do a 3.55 and a Miata 6-speed to match. Gears should be similar to what you have now with an extra cog for cruising. The 6-speed also has shorter drops between gears so the car should be a little faster.

 

Funny you mention that...

I was just in LA about 3.5 weeks ago. My car had no problems hooking. I'm betting you have other problems.


Anyways, the Miata motor is perfectly happy turning those RPMs. If for some reason it bugs you, i'd suggest the 3.73 at the most. Going further will start to suck when it comes to the bottom gears if you're only making 180wtq.

I did 7500 miles of this in 3 weeks and it wasn't a big deal. Do i want a 3.9 or a 3.63? Sure. Is the 4.10 ruining the car? Nah.

 

Lets see upgraded the diff that can easily handle north of 300ftlbs, left the transmission that asplodes at 250ftlbs.

 

I didn't build the car smart ***, I just picked it up as is. Nice try.

 

Doesn't matter either way if he's only making 180ftlbs. I can only imagine how slow that thing is.

 

It might be slower than your car, which is slower than my other cars. Your point?

 

The point is that it's going to be almost unenjoyable going much lower than a 4.10 numerically.


What sort of turbo is on this thing that it's making 240whp/180wtq? That's really bizarre and uncommon, and stupid.


I don't know why we're bringing my car into this. It's not relevant, nor do you know what it is. Get your e-thug on though, hotshot. *** in my ***.

 

GT3571R on low boost

 

his point is you're wasting your time asking the wrong questions.

what you should be researching is a transmission upgrade, then a motor upgrade, and only after all that you should be considering changing the fd

 

I don't think he said how many torques it makes. I just assumed it was 180 because he claimed 240hp. And we all know the horsepowers count.

 

get a proper transmission in there, then build the engine, then turn it up ALL THE WAY and only then go to a low fd like 3.55 or whatever your lowest option is