MX-5 Transmission Guide: Which Gearbox Handles Your Power Upgrade? | SPS Motorsport

When it comes to increasing performance, very few customers deal with the external components such as the gearbox, clutch and differential. However, these components must be able to withstand the corresponding performance as well as the engine itself. Today we will discuss which gearbox is to be used at which power level and which gearbox may already suffer from tooth loss with a relatively small increase in performance and accordingly quit the service.

Let's start with our most popular base for performance increases, the Mazda MX-5 NA / NB / NBFL:
As already mentioned in the buyer´s guide blogs, the two series built from 1990 to 2005 were delivered with 2 different gearboxes (the MX-5 NA only with a 5-speed gearbox, but this can be converted to a 6-speed gearbox without any problems). There are already differences in the steadfastness of these two transmissions.
The 5-speed gearbox (whether from the NA or NB / NBFL) is perfect for road vehicles with turbo conversion. However, you shouldn't go particularly higher than the maximum 250 HP or possibly 320 Nm here. When the racetrack is used and the associated higher temperatures of the components, the transmission also gives up very often. So you should avoid using on the racetrack with 5 speed transmissions in order to protect the components.
The 6-speed gearbox, which can be found in certain models of the MX-5 NB and NBFL, is a bit more steadfast here. This can withstand a maximum load of 300 hp and 420 Nm. In addition, the transmission can also be used on the racetrack. However, you shouldn't ask anything more from the transmission.
There is also the option of leaving the Mazda gearbox out completely, instead installing a gearbox from the BMW E46 330i (GS6-37BZ). This conversion kit will soon be available in our shop and has been tested by us in several vehicles. A significant increase in performance is absolutely no longer a problem here. The BMW's gearbox in the MX-5 NA / NB / NBFL can easily withstand up to 500 HP and 650 Nm and is therefore the highest level of gearboxes for road vehicles and most racing vehicles. 
If you want to increase the performance of your MX-5 even further, the fully sequential Quaife QBE60G is your way to go. This is exactly the gearbox that is also used in our Pro Class racing cars for the German TimeAttack Masters. This is only suitable for use on the racetrack, but it does an excellent job here. With up to 600 hp and 600 Nm, the transmission can cover just about any increase in performance that can be achieved with the original MX-5 engine.

Now we come to the next series, the MX-5 NC:
The MX-5 NC was delivered as standard with 2 different gearboxes, a 5-speed gearbox and a 6-speed gearbox. Here, too, the 5-speed gearbox is weaker than the 6-speed gearbox. With a maximum output of 250 hp and 320 Nm, however, it covers most of the performance increases on a OEM-internals engine.
The 6-speed gearbox of the MX-5 NC can also handle forged engines, but the power should not be higher than 300 HP and 420 Nm, so that you do not suddenly stop due to a gearbox damage. 

Last but not least, the MX-5 ND, which completes the various series of the MX-5:
There is only one variant of the manual gearbox, the 6-speed gearbox. You should make sure that you do not have a gearbox from the first series (the gearbox, not the vehicle), as these already have problems with OEM performance. You can get information on how to find out whether the built-in gearbox is a Series 1 gearbox in our MotorBlog on the subject of "Purchase advice MX-5 ND". The newer gearboxes from the MX-5 ND can then withstand up to 250 hp and 320 Nm.

Do you still have questions about gearboxes in the MX-5? Let us know in the comments on this blog or by email, we will be happy to help!

Your SPS Motorsport Team