MX5Ireland

Hello chaps, just wondering about fitting a six speed gearbox into a mk1 .How difficult is it,what else needs/should be changed,what are the advantages/disadvantages.Has anyone done this and what is it like?
Thanks in advance
Brian

Easy job if its a 1.8 as its a direct swap. You will need the correct diff to go with it or it will be a screamer. 3.9 works well . Put in speedo drive from old 'box and change connectors on one of the 'box switches. Forget which, one is for neutral, one for reversing light. Car is much quicker when driven hard as you are always in the power band.

gearbox , diff, and starter motor - you can use the old mk1 starter motor but one of the 3 bolts will have to be binned as only 2 of the 3 holes will line up.

You really need the correct gearing on the diff ..you need a 3.9:1 or a 3.6:1 ratio

Whats involved in a 1.6? Not as easy?

i think on a 1.6 6 speed swap you need the propshaft aswell.

sidewaysreilly wrote:Easy job if its a 1.8 as its a direct swap. You will need the correct diff to go with it or it will be a screamer. 3.9 works well ..

is the 5 speed diff then a 4.1

scallan wrote:

sidewaysreilly wrote:Easy job if its a 1.8 as its a direct swap. You will need the correct diff to go with it or it will be a screamer. 3.9 works well ..

is the 5 speed diff then a 4.1

what are the details of your car ?
mk1 ? 1.8 ? jap import ?
what trim ? s-special? r-ltd ? etc - it should say on the vehicle information sticker on the door jam on the drivers b pillar

bog standard 1.8 eunos roadsters were 4.1:1
limited edtions were usually 4.3:1

Stick all your info in this table to see the results of various diff, tyre and 'box combinations.

http://www.flyinmiata.com/tech/gearing.php

6 SPEED just adds another gear between 1st and 5th to give a better mid range. First is lower and 6th slightly higher but only drop revs at 120kph by 46 so dont bother if you want better fuel economy as it wont help.

If you plan to go turbo, go for it and put a 3.6 diff in from a uk mk 2.5.

Much stronger box.

Pointless in a 1.6 unless you have uprated to 1.8 rear end.

Thank you all for your replies .I was interested in this as I thought it might reduce revs and noise [keep wife happy] at crusing speeds, but this seems not to be the case.
I think its great to have a forum where all our questions can be answered so well and so quickly.
Thanks again
Brian

charged_rs wrote:

scallan wrote:

sidewaysreilly wrote:Easy job if its a 1.8 as its a direct swap. You will need the correct diff to go with it or it will be a screamer. 3.9 works well ..

is the 5 speed diff then a 4.1

what are the details of your car ?
mk1 ? 1.8 ? jap import ?
what trim ? s-special? r-ltd ? etc - it should say on the vehicle information sticker on the door jam on the drivers b pillar

bog standard 1.8 eunos roadsters were 4.1:1
limited edtions were usually 4.3:1

mines an mk2 rs with a thought has a 3.9
looking for a 4.1 or 4.3

mk2 rs is indeed 3.9:1

i will have a 4.3:1 diff on the 3rd of june from a mk1 rs-ltd im breaking

charged_rs wrote:mk2 rs is indeed 3.9:1

i will have a 4.3:1 diff on the 3rd of june from a mk1 rs-ltd im breaking

how much you looking for it pm me
i wont want it for the next month or so anyway