the real death of nuts was the server migration that VS did tht wiped most of the content, after Darren passed...
I post there to try & keep it alive, same with M5's. I read here daily as theres loads of info

I've been building gearboxes & transmissions for a few years (~30), some gears are a little bigger than a car (~30 tons) so a diff is easier BUT harder

main thing is clenliness and measure / check a few times, if you dont feel happy then theres probably a reason

theres a dimension to set diff-spool bearing preload (cant remember it but will try to find) and this sets them tighter than I like (using the feel or The Force) also drive flange nut tightness sets the pinion bearing preload, you might be able to re-use the old ''collapsable-spacer' but if using new bearings that may need to be set a little tight to account for everything settling - another use of 'the Force'


my diff is based around a Kia 4.778:1 cwp for a na 1.6 being built with throttlebodies / honda b16 pistons & rods feeding a modified 6 speed box (now a 5 speed with 'dogleg' first) and multiplate clutch, diferent power levels to yours & most here

Rich.

 

When you say the collapsible spacer do you mean the crush tube? I ordered a full bearing kit from Bofi Racing that has all the Koyo bearings, seals and a new crush tube.

Your build and experience sounds interesting! have you got a build thread somewhere? I did look around for information on rebuilding the gearbox too but couldn't really find good information on it, or any bearing/mesh kits, have you done this? Seems a shame to have a fully built engine and rebuilt diff to then leave the gearbox alone connecting the two!

-Lew

 

thats the one

link in sig?

what gearbox? the 5 speed is a little harder to strip than the 6 speed
I found a pdf of the Mazda workshop manual online somewhere that covered the 6 speed but when I've stripped 5 speeds its just been done using guesswork & (un)common sense
as to bearings, I usually visit a local bearing-supplier or order from internot using bearingnumbers or dimensions as kits from the likes of bofi can be expensive....

with the 6 speed I've got it was part-stripped to fiddle with the selectors & alter the breather, its retaining standard gears but using second as the new 'first' in a 'dogleg' pattern with a mecanical 'lockout' (bolt) to stop selection of the origonal first gear. I've made a longer gearstick using 13mm dia steel rod and a pair of 'spherical bearings as pivots with an adapter sleeve to fit the origonal gearchange turret - lots of thinking and measuring with a few hours playing on my lathe...




didn't see reason to dig deeper as the box was supposedly good (bought from a 'known' source) and this is as a test...
my previous intention re. gearbox was to use an auto-bellhousing & machine an adapter-plate to fit a Ford 'type 9' 5 speed (sierra based) with a Tran-x straight-cut / close ratio gearkit but this complicates things for my intended use of sprint & hillclimb where the origonal gearbox type OR gearcaes must be retained

if I wanted to leave 'road-modified' & enter in the 'open' classes I'd probably swap the engine for a dry-sumped Vauxhall XE 2L that I've got (supposed to be going in my 1978 Vauxhall Chevette 2300HS rallycar project - but this has been ongoing for ~20 years) & the ford / tran-x gearbox BUT this adds massive costs getting the rest of the car up to safety-standards with a full cage (2020 rule change means more bars) anf fia legal seats helmet & hans device.

too many cars, too many toys, too many ideas & some ADD thrown in does not help

Rich.

 

re. the gearbox pdf, heres the link to someone's google drive (I have no idea who but thank them for uploading )

https://drive.google.com/drive/folde...EdwS0xSNGVXMzA

found while scraping google for goodies

Rich.

 

I like what you did with the linkage. Do not get the whole hassle of converting the 6-speed to a 5-speed unit tho; especially since it is heavier and more expensive. What am I missing?

 

I'm using 2-6 gears as a close-ratio' 5 speed gearset, this combined with the 4.778:1 final drive will suit the normally asperated 1.6L (well, overbored to 1.7L) engine for the motorsport I'm intending to run in,
second gear on the 6 speed is 2.27:1 and 3rd @ 1.65:1, 4th @ 1.23:1 and 5th @ 1:1 are comparable with 'race' & 'rally' ratio gearkits

FM's calculator to the rescue, it's doubtfull if it'll ever get to top revs in top gear or top speed, out of corner & uphill is the aim

comparing the few kg's extra for the 6 speed to a 5 speed then possibly a quaife gearkit @£2K is a no-brainer! (also I've rebuilt many of their gearkits / diffs & don't rate them )

if I'm lucky I'll find a 5.1:1 fd & that'll improve matters but they're sorta rare......

also, UK & US prices differ somewhat, prices here are significantly less than in CONUS for cars & used parts (but new prices are sinilar) so the 6 speed cost ~$200 but the car it came from probably cost the same

Rich.

 

They're some cool posts Rich, sounds like you have some interesting experience!

I was let down this weekend when the skip firm didn't deliver a skip before the bank holiday weekend... so now I have a few days to myself with the car, and a genuine excuse about why I can't work on the house/garden. So I continued stripping the shell back. I'm not at the point where the only thing left is the fuel tank which I will pull soon. I was an incredible faff getting the wiring harness out but eventually it came out. God help me putting it all back in and figuring out what everything connects to though lol.

My plan is to run a stripped interior for a few reasons, the main one that Mx5's aren't perfectly water tight and the carpets I've taken out were minging tbh, like water had sat in them for a long time, and given the car that musty smell. At least without carpets if water does get in it'll probably just evaporate... although I intend on replacing all weather seals with new ones. 26 years later the originals are hard and perished. The other reason is that this car is not a daily, it'll only get driven in good weather and on those days I do drive it, I want it to be different to a regular car, something crackers that puts a bit grin on your face. And weight... I can't believe how much the whole lot weighs! I suppose the thick nasty 30 year old insulation doesn't help.

Anyway, some pics.



I suppose today marks the start of the rebuild, now that there is no more stuff to take off the car I have turned the corner and can now start rebuilding/buying parts to put back in! I'm going to start with refurbishing the parts that are going back in directly, then the underside which I already have most of, and then I think I will get around the exciting stuff like the turbo setup, but initially I want to put the car back together in such a way that I can drive it naturally aspirated to get it's MOT done so I can tax it, and drive it... and then start putting the turbo parts on.

-Lew

 

Well I best update this again as quite a lot has changed in the last few weeks/months... however long this lock down has been going on for.

Having had so much time to think, and do some maths I realised that it's probably actually cheaper or about the same cost to K swap my Mx5, rather than finish off the turbo build. I figured that out on selling the engine and buy K swap parts vs having to spend the extra amount buying turbo, manifold, intercooler etc etc.

So I put the engine up for sale, it sold within an hour, collected within a week for good cash, and a week later I got a K24A3 delivered. Now that roughly translates the the US version of the K24A2.

Now I did look at just grabbing a K-Miata kit and using that but then I started realising there's a few issues with that, due to the steering column being on the right, this doesn't work with their subframe and exhaust header, so I thought ok I'll get those bits done over here, so I got in touch with some guys I know who are automotive engineers/fabricators and they started figuring things out and now it looks like I'm probably going to have the whole swap done here in the UK. After doing some maths I discovered that it's wasteful to be paying for expensive shipping and import duty on the K-Miata parts to then have to continue working with them anyway.

I stripped the engine down anyway, took off all the parts I won't need on there for now, I'm going to look at swapping the head for one of the better flowing ones, the plan is to create a strong NA motor from this, hoping for around 260-280whp in the engine which it seems possible from a K24 bottom end and K20 head. Might look at supercharging it later down the line but I really feel like the sweet spot for me would be an NA screamer.

Gear box wise I think one of the guys doing the fab work will help decide on that, I don't think we'll be sticking to the Mx5 box so it'll be interesting to see what we come up with.

All in all, a pretty exciting build ahead.

Some pics:




-Lew

 

I could do with getting some input on here about a few things, mostly K-Swap related.

So the engineers that are looking at creating all my parts are asking what gearbox I want to run, obviously a Mazda 6 speed is a fairly straightforward option, and means less fabrication work, but also means it probably is going to die, especially given that I may build an all motor engine eventually, or supercharge this one. Immediately taking me over 350bhp, maybe over 400 from what I've seen on some builds, so I think I'm set on having something really robust from the get-go with this.

Now looking at Kmiata, they like the ZF boxes, and the Getrag 260. These are options I like, I think personally I'd be looking for the Getrag 260 as I prefer the longer gearing.

But having spoken to some others, there's options like the J160 gearbox from a Lexus IS200 (I think) I can get those for almost nothing over here, and a guy who's doing some of the work for me has seen these regularly in 500bhp drift cars and some 700bhp monsters. So it seems they're up to the job, but I wondered how they might fit, and how will I get a reading for my speedo?

These aren't the only options, if you could go for any gearbox, what would you go for and why?

The Getrag 260 and J160 are front runners for me at the moment due to strength and availability/cost.

Which leads me onto getting the speedo drive from them... obviously my NA has a mechanical speedo drive and that later switched to a digital one in NBs, should I convert to an NB cluster (already dash swapped) to make things easier with respect to the speedo?

 

unless you want vss for ecu input (cruise??) I'd just get a gps speedo
you can get proxi-sensors that can be mounted on front hubs (to read wheelstuds / 4 @ a revolution) and use this to convert to run an electronic speedo (front being more reliable for accurate wheel rotations)

like

https://www.demon-tweeks.com/uk/terr...probes-249606/

but can be found cheaper (I've a few used sensors from old rallycars if you want one to play with? FOC)


Rich.

 

On the speedo... I'm trying to get some GPS/Arduino based thing going for the NA. GPS Module gets speed data, arduino then takes this data and controls an RC car ESC/ Motor to spin the cable that goes to the cluster. I'm waiting on the GPS module to ship as I've got everything else already.