6sp in a Mk1

[snotrag]

Easy question - does it go? The engines are the same, and the chassis is roughly the same, so ~I'm hoping its as easy as a straight swap...?

[SunDiver]

Yes if you mean a six speed from a Mk2. As ever with MX-5s check out www.solomiata.com and
specifically the drivetrain page at http://members.aol.com/solomiata/Drivetrain.html

He writes...
Will the 6-speed bolt in a 5-speed Miata? Yes, make sure to get the trans plate and shifter from the 6-speed donor since they are unique to it. You will have to use only two of the three 5-speed starter bolts but that shouldn't be an issue, otherwise it bolts in (same PPF mount, etc). Keep in mind the 6-speed is combined with a 3.909:1 rear in the USA (3.636:1 other markets) since the tranny gearing is much steeper so your '90-93 or 99+ 4.30:1 5-speed rear should also be changed to the 3.909 or at least the more common 4.10:1 otherwise you'll have a nice tree stump puller

Richard at Maztek in Telford (Mazda indie) ran a 6 speed in his heavily modified Mk1. Quite a few others have also done it. I also ran a Mk2 five speed in my Mk1 for a while - there was some suggestion they were stronger boxes - my '5 ran a 250hp turbo.

I'm pretty certain that all Mk2 boxes use electronic speedo senders so you need to put the mechanical one from your Mk1 box into the Mk2+ six-speed.

Edited by SunDiver on Monday 21st April 21:17

[snotrag]

Thanks - I presumed as such.

I don't actually own a Roadster yet, but it is still something I am hoping to do, probably in the Autumn now.

Been harping on about it on this forum for ages, and have had another car since I started looking at Mazdas - couldnt find one that came up to my high standards last time and it was Spring so prices were going up!

The 6Spd box is one of my favourite facets of my current car, I find it add so much to the drive and increases involvelment, along iwth improving acceleration. Also the Roadster will be my only car and a slightly taller top gear would be very useful on the motorway.

The box is avaialbe quite cheap and it would be a nice little project for me aswell!

[MX-5 Lazza]

Don't get too hung-up on the 5-speed/6-speed thing. The only real advantage the 6-speed has is slightly longer gearing in top gear as long as it's mated with the right dif.
The 5-speed has the better gearchange and the ratios are perfectly matched to the engine characteristics. You never feel like you need an extra gear unless you do a lot of motorway cruising - in which case why have an MX-5?
My current car has the 6-speed but it's not as good as the 5-speed in my old Mk1. The gearchange isn't as positive and I've found myself "lost" in the cogs a few times, especially on track when going through the gears quickly (with 225+bhp it does go through them quickly).

[GHW]

^^ what he said.

The overall top end is almost exactly the same in the 5 and 6 speed boxes - so all you'll get by swapping to a 6 speed is closer gear ratios. If you want a higher top-end you'll need to change the final drive in the differential as well.

[snotrag]

If I get one it will be an only car - so yes, this will mean it finds itself on the motorway quite often.

As for Ratios, I appreciate 6th is not much taller than top on a 5spd box.

However this is the case with my current car aswell, which shares a similar engine to the Mazda. IE, Naturally aspirated, 16 valves, high revving (Peak at 7000rpm redline at 7250) and I find the gearbox matches it perfectly.

In effect, it has the same top and bottom as the 5 spd, but with 4 cogs in the space between instead of 3. It does mean your changing gear a lot, but it means the engines always on the boil and you always get that punch out of the corners.

Anyway, I'm not reading too much into it, and its just something I will consider as a bit of a project if I do get one. Its certainly not going to stop me buying one, as I've found the snickety 5spd great in cars I've test driven.