Can I make my gear ratio longer on my miata?

1991 Madza Miata 4cyl 1.6 RWD



I'm tired of doing 70mph at rev of 3800 or so, I know it has to do with the differential. Is there a forum or a shop in southern California that can help me with this mod?Can I make my gear ratio longer on my miata?
First off, these motors are fine doing those rpms for an extended amount of time. Since you are driving the 91 odds are it has the 4.30 gear. What a lot of us have done is purchase the rear end out of a later model NB. The 4.10 is not much of a change but the 3.90 torsen it is a good swap for what you are looking for. To do the swap you will need the entire rear end pumpkin (easiest method), halfshafts, and drive shaft from the NB model car. You could go as far as the 3.63 gears, but for the 1.6l you will be having a lot of issues starting with such a tall gear. Highway speed will be great and much lower rpm, but taking off from a dead stop will be tougher. I have done the 3.90 torsen swap from a 99 and I really enjoy the difference. At 80 mph I am cruising about 3750 rpm...at 70 mph I am around 3250.Can I make my gear ratio longer on my miata?
The problem you are going to run into is torque. those little motors aren't designed to have that much torque, you will be putting undue stress on your engine.