Gearbox information needed

ondman88 · Postby **ondman88** » Thu Dec 19, 2013 10:46 am

Hello Mx5 Car Talk People

I have what I believe a 1.6l gearbox and a 1.8l gearbox. The 1.6l gearbox is on the engine that I'm supercharging and putting in my car. The 1.8l gearbox is on my old engine that is not going in the car, currently. The 1.6l has a heavy duty clutch as the engine had been turbod.

1. Are there any identifiers to know that one is a 1.8l and the other a 1.6l gearbox?
2. Will the clutch be able to go on the 1.8l gearbox?
3. Is the 1.8l gearbox stronger and therefor worth changing over?

Any information would be much appreciated as I'm at a pickle.

plohl · Postby **plohl** » Thu Dec 19, 2013 11:37 am

Pretty sure the gearbox's themselves are the same. You can get different fly wheels for each model, IIRC people switch from NA8 to NA6 flywheels because they're lighter...

hks_kansei · Postby **hks_kansei** » Thu Dec 19, 2013 11:47 am

Gearboxes are the same bar a few minor ancilliary changes (gear stick, speedo sender) assuming they're both 5 speeds.

Late NBs were available with a 6 speed, which obviously, is different.
The 6 speed is a bit stronger if I recall, and I think has shorter ratios?

ondman88 · Postby **ondman88** » Thu Dec 19, 2013 4:45 pm

Thanks everyone for you help, they are both 5 speeds, if they are no different I wont bother changing them.

Regards,
Andre

tescoking · Postby **tescoking** » Thu Dec 19, 2013 6:09 pm

Only different will be 5spd or 6spd, 1.6 or 1.8 will still be using the same gearbox. Otherwise everyone who have turbo will need to change their gearbox too

93_Clubman · Postby **93_Clubman** » Fri Dec 20, 2013 10:25 am

93_Clubman wrote:Very slight differences between NA6 & NA8 GB: http://solomiata.com/Drivetrain.html

"Mazda has two 5 speed transmissions. One is used in NA applications (AKA 'type 2' or Model M) and came on such cars as the RWD 626, 79-85 RX-7, 86-91 NA RX-7, B2000/2200 truck, and Miata. The other is a stronger unit that came on all turbo RX-7's, 929, B2600, and MPV.

Within the type2 versions only the bellhousing & tailshaft cases and gear ratio's are really different between models. All the guts of the Type 2's are nearly the same and mostly interchangeable. The major differences came in '81 when the shifter was made remote, in '83 where some bearings and shafts were made larger and in '94 with improved seals and a double cone 2nd gear synchro. Between models the input/output shaft lengths may differ slightly (~ 1/2") so always measure. The 79 through mid-83 tranny guts should be avoided if reliability and torque rating is important".

viewtopic.php?f=29&t=56291

geofiz · Postby **geofiz** » Fri Dec 20, 2013 6:27 pm

From first hand experience, the NA6 and NA8 gearboxes are same. The NB 5 speed is sligfhtly different, the only external difference is in the shifter mounting.

Internally, they have the same ratios, but the NB 5 speed has more robust synchro rings.

If the speedo drives are still in palce, the NB uses and electric drive while the NA uses a speedo cable.

Hope this helps.