Gearbox upgrade - MX5 to M series engine

I am having a lot of fun in my car at moment..... dare I say... on TARMAC...

The new exhaust has allowed my 1300 to breathe much better and I have little complaint about the engine now, the gearbox however is a different story. The biggest issue is the big hole at the bottom of 2nd gear, the car bogs in slow 2nd gear corners.

I have considered many options but the one that has presented itself as financially viable (but still quite costly) is the MX box. It has a shorter 2nd and will allow the engine to stay within its power band in those tight 2nd gear corners. In addition, the box is close ratio'ed and very short shift, a pleasure to drive with.

A local engineering company that is quite heavily involved in motorsport has said that they will produce a bell housing to mate the engine and box together.

The conversion kit will be around £500 if I can get a batch of 10 produced, would there be any interest from other forum members ?

sniper

I'm trying to remember the hole in 2nd you refer to it certainly didn't seem too boggy when I had a wee drive?

I know what John means. There is a larger 'gap' between 1st and 2nd, than between 2nd and 3rd, 3rd and 4th, etc. I notice it as increased noise from the rocklobster at low revs, as well as not getting going very well from low revs

The ratios for the Jimny are in the wiki (look at M13 R7me gearbox for this comparison):
www.bigjimny.com/mediawiki/index.php?tit...ssion_gearing_ratios

And the MX5 has much smoother progression through the ratios (and is 6 speed):
www.miata.net/garage/KnowYourCar/S8_Gears.html

The £500 kit sounds interesting, does that include a mini prop (assume it'll need a custom one?) and some form of mounting bracket altering probably too?

Lambert - It only "bogs down" in tight slow corners with no punch to get going, you'd almost shift to first but then you have still got the big gap to get around... Not really a problem on a normal car, you just tolerate it and accept that momentary lack of progress. Being a gentleman, you didn't push my car that hard when you drove it.... or have the type of corner that causes a problem...

Riccy - No prop or mounts, it's just the bell housing and maybe some flywheel work.... It will need to be fitted and the mounting problems resolved but it does look doable... The shifter location will be very slightly back from standard but a kinked gearstick should make it good.

sniper

I don't want to burst your bubble but my the MX5 gearbox is a massive 32" long compared to 19" for the Jimny. It leaves barely 6" for a transfer case propshaft.

Also, if you are going to the trouble of fitting the gearbox, you might as well leave the MX5 engine attached and spend the £500 on an ECU instead. I bought an MX5 for precisely for this reason but the length of the gearbox made it massively more complicated than I had initially hoped. I took the alternative route of lifting the MX5 and fitting some all-terrains and it's epic.