Gear Ratios : Speeds In Gears : When To Shift a Skyline GT-R

This post is all math. If you don’t have some math, to fill into the blanks, you can’t figure any of this out. What you need to know:

Tire Height – can be calculated from
- Width
- Aspect ratio
- Wheel size
- https://spicerparts.com/calculators/tire-height-calculator
Transmission in the car
- Is it stock?
- Is it modified?
- 5 speed
- 6 speed
Overall Gear ratio
- 4.111 is stock R32/R33 GT-R
- 3.545 is stock R34 GT-R
- It can be something else
Shift Point
- If you shift with the stock tach you are shifting at 7600 rpm
- If you shift at the limiter then that is most likely 8000 rpm
- If you shift at a different point, the links are below to figure that out

Gear	1	2	3	4	5	6
R32/R33	3.214	1.925	1.302	1.000	0.752

R34	3.827	2.360	1.685	1.312	1.000	0.793

One example, my bluecar. It has a 275/35/18 tire on it, which is 25.58 inches tall. It has a stock 5 speed transmission. Overall/Final gear ratios are 4.111. It is shifted at 8500 rpm.

https://www.blocklayer.com/rpm-gear.aspx

4.111, stock transmission, shifting at 8500 rpm.

4.111. stock transmission, shifting at 8000 rpm on the stock tach, aka 7600 rpm.

So you can see that by shifting at a higher RPM, you fall into a bit better point on the dyno chart for this car, and this turbo combination. https://www.gtrusablog.com/2019/10/finally-running-bluecar-on-dyno-results.html

So about if we swapped to a Getrag? Well actually the bluecar used to have a Getrag in it, but we sold it to a friend, that needed one. So add a 6th gear, keep the 4.111 gear vs the 3.545 gear of the R34. Then we get: