6MT complete

If we use NB’s 6 speed transmission in NA we can have a very pleasurable drive.
We can say that it is a very convenient tuning because at the time of installation there is no need for processing.
Two types of 6MT are available: one for NB non-turbo and one for turbo. As there is no official announcement from the maker, we cannot make a conclusion about the exact differences.
However, according to comments in magazines, surface treatment is carried out on the gear for turbo.

Maruha recommends a 4.1 final.
This is the best gear when considering the cross-over ratio.
4.3 is not bad either, however, in that case the first gear becomes quite low.
Here we don’t want to talk only about a good circuit time but also about everyday use.
Maruha thinks that from the start 4.1 should be used instead of 3.99.

About the installation

The 6MT can be set up in any of NA6, NA8 and NB6 cars. The flywheel and the clutch can be reused.

The starter motor in the case of NA and NB is fixed at 3 points but the bolt hole at the center is different, so when reusing the NA starter we fix it only at 2 points.

The coupler of the back switch is different too, that’s why a little bit of wire processing is necessary. When purchasing through Maruha, you will get an exchange harness.

The gearshift is for 6MT; 5MT doesn’t fit.
There is no need for further processing on the body side either.

O/H and durability

When using 6MT under severe conditions the possibility of arising problems might be higher than in the case of 5MT but in reality you can use it safely and with very stable efficiency in circuit attack too.
In the case of usual cars we can say that there is no arising problem.

6MT gear

Final 3.909 4.100 4.300 4.100
1st 3.760(14.697) 3.760(15.416) 3.316(13.485) 3.634(14.899)
2nd 2.269(8.869) 2.269(9.302) 1.888(8.118) 2.372(9.725)
3rd 1.645(6.430) 1.645(6.744) 1.330(5.072) 1.718(7.043)
4th 1.257(4.913) 1.257(5.153) 1.000(4.300) 1.347(5.522)
5th 1.000(3.909) 1.000(4.100) 0.814(3.500) 1.125(4.612)
6th 0.834(3.260) 0.834(3.419) 0.940(3.854)

Low gear ratio
High gear ratio

On the left, the upper gear chart represents the cross-over ratio in a graph. If we compare the curves of NB6MT, S2000, NB6MT and NA5MT we can see that the NA5MT’s curve is not smooth.
This means that the connection between the gears is not good.
In the case of 6MT the connection is good but we have to pay attention to S2000. Even though a high power engine is installed, the gear ratio is low.
This can mean that the stress is on speeding and high revolution.
In the case of Miata/MX-5 we cannot get high revolution easily but we can reach a gear ratio with a stress on acceleration.

Please feel free to contact us with any questions.


Maruha Motors Co., Ltd.
Ushizuma 2095-6, Aoi-Ward
421- 2106 Shizuoka city, Shizuoka prefecture
TEL: 0081-54-294-0076
FAX: 0081-54-294-1312
E-mail: info@maruhamotors.co.jp