5 speed gearbox

[DaveJC]

Hi. Has anyone fitted a 5 speed Mazda mx5 gearbox to a 1098 engine?

I've got the engine plate and starter motor sorted and I'm at the point of working out the clutch.

My original plan was to use the Morris pressure plate with a modified mx5 friction plate until I realised the spring type pressure plate used by the Morris is too deep and wouldn't fit and a more compact diaphragm pressure plate would be needed.

What I'd like to know is if anyone has carried this conversion and if so how they got around the clutch issue?

[win]

Morning
I fitted a Mazda 5speed MK1 gearbox to a 1275 midget, but similar block.
I found a 190mm diameter pressure plate, ID numbers CK9831 or 3767, to fit CITROEN PEUGEOT or TOYOTA.
There are a couple on eBay 175602279486 or 186826499321 which look ok
Used a standard Mazda clutch plate, but had to machine 5mm from the outside diameter, used standard Mazda release bearing.
Have you moved the gear stick forward?
Regards Win

[DaveJC]

Hi Win
Thanks for your reply. I must be on the right track then as I've bought a clutch made for a Mazda 323 which arrived yesterday afternoon. I've offered it up to the Morris flywheel and it looks a good fit and even the fixings holes almost (but not quite) line up.

Did you need to get the flywheel drilled and tapped to suit the pressure plate or did you have the pressure plate fixing holes altered? Did you have dowels fitted to the flywheel?

I've got a standard friction plate but as you say, it needs the diameter reduced by around 5mm in order for it to fit under the 323 pressure plate.

Looking at the rivets they aren't central on the friction material being nearer to the outside diameter.Is there any issue taking 5mm off of the diameter making them even nearer to the outside?

How was yours done, was it on a lathe?

I think the gearbox I have is from a Mk 1 as it has the exposed gear change tube which I think is ideal as I'd need to move it as far forward as possible whereas the later ones seem to have just two options.

I've been reading a post explaining how it's done and it looks quite doable.

By the way, how do you find the Mazda box? Is it as good as people say?

Best regards
Dave.

[win]

I have misplaced my bible, referring to everything I have done over the last 37+ years, so I am relying on my memory, it's not reliable.
I did mine during lockdown, so limited access to human contact.
I had to slot the holes in the pressure plate outwards by a very small amount with a round file, checking how much removed with a vernier.
I had to redrill dowels.
I removed the 5mm off the clutch plate by grinding, and checking again by measuring, I don't remember having any problems.
My engine is midget 1275, so on the motorway it is very rare to come out of 5th even with a 3.9 diff and a trailer tent, so a good modification, with 38 to 40 MPG.
Good luck, enjoy yourself.
Regards Win

[DaveJC]

I was tempted to do the same as you by filing the holes outwards as it only needs a very small amount but I was a bit nervous of putting it out of balance but i think I'll have a go.

Thanks for the information you've given, it's very much appreciated.

Best regards
Dave.

[oliver90owner]

It is the dowels that fix the position of the pressure plate. Personally, I would enlarge the holes by the absolute minimum with a rotary table or a dro on a milling machine, but your filing is likely adequate if you have no alternative.

Even reaming the holes might be an alternative. How far off are the bolt centres?

[DaveJC]

Unfortunately I don't have a milling machine.

I've started on filing two opposing holes at a time very carefully measuring as I go to keep it an even amount on each hole taking off the minimum amount.

Measuring the hole centres on both the pressure plate and the flywheel there is a difference of 2.5mm so I'm aiming to take 1.25mm from each side.

I'm supposing I then need to drill holes for the three dowels once I have the plate in position.

[win]

That is the way I did it, best you can do.
Regards Win

[DaveJC]

Hi Win,

Another question if you don't mind.

What did you use for the clutch pressure plate dowels? Did you make them yourself from steel rod or did you source some stepped dowels?

If you made your own from steel rod did you use any adhesive to secure them?

Regards

Dave.

[win]

I used stepped original Morris Minor dowels
Regards Win

[DaveJC]

Thanks Win.