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Which MX5 gearbox for a Duratec?
John G - 20/11/19 at 05:48 PM

Having read a few threads on the MX5 mkIII gearbox, can anyone advise on the difference between the 1.8 bad 2.0 litre engine gearbox? Ratios strength etc.

sdh2903 - 20/11/19 at 07:30 PM

Needs to be a 5 speed. It's the same box in the 1.8 and 2.0. Designated the mk3 NC gearbox and the box is an N7 gearbox.

Ratios and more info here

peter030371 - 20/11/19 at 10:17 PM

I thought opinion was go for the 6 speed but don't bother using 1st. If 1st is 3.something with a duratec in a light weight car it's no use unless you are towing with it

sdh2903 - 20/11/19 at 11:02 PM

I had the 5 speed mated to a 2.0 ecoboost and a 3.62 diff and the 1st gear was absolutely fine, infact its a very well matched box to a duratec/ecoboost. the long first versions of the type 9 start at 2.98 so its hardly a million miles away, and the mazda box is around 1500 quid cheaper.

The 6 speed is bigger therefore slightly heavier, more expensive and not as strong as the 5 speed.

Ive also never been a fan of using compromised gear boxes and missing out 1st.

peter030371 - 21/11/19 at 08:50 AM

Just checked and I was thinking of the RX8 6 speed box, seems others have used this as a '5 speed' box as again 1st is not a suitable ratio.

Without knowing your tyre sizes and diff ratios plus your intended use (road, track or mix of both) its difficult to say 100% what will suit you only you can work that out

For your information I have a road legal but track focused Striker with a Duratec engine producing 189bhp on the rolling road. My gearbox is a type 9 with 2.39/1.56/1.26/1.00/0.87 ratios and a 3.92 diff. Tyres are 205/60/13 and it is just fine driving it in traffic and pulling away.

andyhaase1 - 28/1/20 at 07:12 PM

I built a MNR VORTX with a duratec and a Mark 3 mx5 1.8 box, with a 3.62 sierra diff. I got it iva'd and on the road back end of 2019. I've done probably 400 miles so far, road only, and its quite high geared, but has enough power to overcome it. The guy who mapped it said it was geared for 140mph top end, I built it for trackdays, so i might find it needs a lower final drive diff.