Transmission Gearing

'00 Miata Transmissions, US options

Final Drive	4.30	3.91
1st	3.14	3.76
2nd	1.89	2.27
3rd	1.33	1.65
4th	1.00	1.26
5th	0.81	1.00
6th	…	0.84

Speeds in different gears assuming a 3.636 rear end on the 6 speed:

80 mph 5th	80 mph 6th
4080	3573
80 mph 5th	80 mph 6th
3060	2679
80 mph 5th	80 mph 6th
3446	2914
80 mph 5th	80 mph 6th
2819	2384
80 mph 5th	80 mph 6th
2916	2331

A nice solution for a turbo car would be the 3.901 rear end with a 5 speed, many 10 AE owners do this by removing their 6 speed.

Gear Spacing (percent):

1 -2	66.1	65.37
2 - 3	42.0	37.9
3 - 4	33.0	30.9
4 - 5	22.9	25.7
5 - 6	…	18.6

You can see with the 6 speed, the first three shifts are shorter, keeping the gears closer together. The shift to 5th is a bit taller than it would be in the 5 speed, and 6th isn't as big a step as just "adding another gear".