Turbo 1.8 NA, 240whp, 7.5 Ford rear, what gears?
#1
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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!
![](https://www.miataturbo.net/images/smilies/smile.gif)
#2
Elite Member
![](/mt2011/images_td/ranks/supporter1.gif)
iTrader: (5)
Join Date: Oct 2011
Location: Detroit (the part with no rules or laws)
Posts: 5,683
Total Cats: 805
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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.
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.
#8
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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!
![](https://www.miataturbo.net/images/smilies/smile.gif)
Sincerely,
Someone who makes more power than you yet manages to dead hook 1st, 2nd, and 3rd with a 6spd and a 4.10.
#9
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
This forum is spicy, I like that ![](https://www.miataturbo.net/images/smilies/smile.gif)
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.
![](https://www.miataturbo.net/images/smilies/smile.gif)
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.
#10
Former Vendor
![](/mt2011/images_td/ranks/supporter1.gif)
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,103
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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.
#11
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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.
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.
![](https://www.miataturbo.net/attachments/suspension-brakes-drivetrain-49/84585-turbo-1-8-na-240whp-7-5-ford-rear-what-gears-20130629_173836.jpg?dateline=1375385111)
#16
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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 ***.