Gearbox & Clutch identification

[ian65]

This is a copy of one of my old posts from last year and identifies 1st gen gearboxes and clutches...

Gearboxes.
S2 & S3 boxes look the same and either will bolt up to either engine s2 or s3.
The splines are the same and will run either clutch 215mm or 225mm.
The internals however are slightly different. The way to identify which box you have is to undo the 10mm bolt and pull out the speedo drive.

A s2 box has this green drive with a coarse pitch....



A s3 box has this drive with the fine pitch....



neither drives are interchangeable. The fine pitch s3 drive gives the correct ratio for the 14" s3 wheels. Drop in a s2 box and your speedo readings will be out.

Clutch
The 215mm clutch plate will fit a s2 gearbox
The 225mm clutch will only fit the s3 engine.... this is because the flywheel is different between the 2 engines.
The s3 flywheel is has a wider mating surface to accomodate the wider clutch plate.

Elford put 165bhp through the 215mm clutch so that would suggest a 215mm clutch would be more than good enough for a n/a S2 running slight performance mods such as a free flowing exhaust.
The difference in price between a new 225mm clutch and a 215mm one is huge.... 215mm clutches can be bought complete on ebay for around £30..... 225mm clutches are lots more.

[chc]

Very interesting topic this one.
In all cases I've read, the common factor has been putting an S2 box into an S3 body.
My question being - JAZ (my current roadworthy) is an S2 fitted with an S3 engine. I've noticed recently that the speedo reading (80 mph) did not match up to the satnav indicated speed (72 mph) - I'm more inclined to believe the satnav due to the technology built into this gizmo, so I'm wondering whether I also have an S3 box fitted into an S2 body? On the basis that dropping a different series box into a different series body, could this different speedo reading be overcome by changing the dashboard odometer or am I just talking rubbish

[ian65]

Most speedo's overead to some degree, even on modern cars which is why police don't prosecute you if you're doing 31 in a 30.... they allow for a degree of error.
The only way to check if your running the correct s2 gearbox Cliff is to pull the speedo drive and look at the colour of the cog.... easy 5 minute job if you can get under the car.
My black series 3 over-reads in comparison to the satnav as well and I'm definitely running the correct s3 gearbox.

[codge]

Very interesting topic this one.
In all cases I've read, the common factor has been putting an S2 box into an S3 body.
My question being - JAZ (my current roadworthy) is an S2 fitted with an S3 engine. I've noticed recently that the speedo reading (80 mph) did not match up to the satnav indicated speed (72 mph) - I'm more inclined to believe the satnav due to the technology built into this gizmo, so I'm wondering whether I also have an S3 box fitted into an S2 body? On the basis that dropping a different series box into a different series body, could this different speedo reading be overcome by changing the dashboard odometer or am I just talking rubbish

Doing my 'ed in with this but I reckon the speedo's will be the same?

I think Mazda will have corrected for the different wheel diameters at the gearbox, hence the different drives, Green or Black. The mechanical drive cable up to the speedo will therefore rotate at the same number of revs per mph on each car if the right series g/box is fitted.....?????? Or is that a load of old cobblers?

[ian65]

I've never compared parts numbers for s2 & s3 speedo but I agree with Dave, I reckon the gearing is controlled by the speedo drive at the gearbox and I'd imagine the actual speedos are the same...... unless anyone knows differently.

[chc]

I'd also go along with that philosophy (my what a gr8 word for a Saturday night after a few beers ) of the speed being goverened within the gbox but just thought I'd throw in a curved ball to see what sort of reaction it would have and there is nothing wrong with a different approach afterall.

[Johnnyboy]

Are FB speedos even worse than most other cars? I know they all read fast, but Miss January (an S2 with an original S2 gearbox) with Elford 205 60 13" wheels, has a speedo which reads a good 13%/14% fast (compared to GPS) - which is a lot....

[Lucky]

Just for reference, my S3 with stock wheels is just as erratic. It's spot on the GPS until ~60mph, after that gets progressively farther apart. Which is odd, you'd think it'd be linear, but there you go. For a genuine GPS 100mph you need 115 on the clock. (On private roads). I dunno what happens after that, I was a bit too conscious of the 15-year old tyres

[ian65]

at 90mph on the clock mine shows 82mph on the satnav

[spirit r]

S3 gearbox S3 diff, 225x50x16" wheel rear. 62mph (100km/h) on the clock exactly 62mph on the satnav.
so it´s important what tires model on your car.
Johnnyboy S2 with 205x60x13 is different to 185x70x13 OEM so the problem are the tires size.
Thomas