Gearbox upgrade - MX5 to M series engine

Have you looked at the lexus IS200 box...

www.cars-data.com/en/lexus-is-200-executive-specs/20630/tech

Similar numbers and I think its what Keith is hoping to use

re the viscous coupling - could this be a cush drive type idea to smooth it out somehow?

Busta - I dont think John is after quite the performance style of the MX5. Ive driven his before the chop and tis surprisingly nippy for a 1.3 and a lot faster than many standard Jimnys ive driven (faster than my 1.8 was then too), The further mods should help, along with the weight loss. I agree that the gearbox change purely because of ratios is a bit much, but some improvements are to be had from the 6 speed arrangement and the slightly smoother progression through those gears, making two good reasons to look at it

I hadn't considered the Lexus box at all Riccy..... It is a nice gear set but I've never driven one....

Keith sent the CAD files as mentioned and also sent some pictures of his freshly machined alloy weld on bell housing adapter. Super impressed, he"s quite the engineer.... I eagerly await his progress. He might have a customer before he finishes the job lol. In the meantime, I am going to go for a test drive in a manual Lexus if I can find one in a local dealer....

I will be speaking to the CAD designer either later this week or early next, whist there, I will ask as to why viscous couplings were mentioned, they may do something with them on their built cars. Intriguing.....

Busta - I feel that no matter my approach to the car, you would be negative, you seem to be that way...... If you could have "no interest", that may be best....

sniper

I would fit a Quaife box at the drop of a hat Lambert, happy with a 4 speed but even that is around 2k..... Sadly the car does the brraaappp thing now lol, just not the go to match

sniper

sniper wrote: Busta - I feel that no matter my approach to the car, you would be negative, you seem to be that way...... If you could have "no interest", that may be best....

sniper

I do have an interest, hence involving myself in the discussion and sharing my experience from similar investigations into the compatibility of MX5 parts with the Jimny. If I come across as miserable it's because I struggle with all the bold claims, waxing lyrical and hyperbole. Unfortunately I'm only actually interested in what works and what doesn't.
You seem to object to me pointing out some facts that I have learnt from my own research into the matter. I'm always happy to be corrected if the information I've given is wrong but you dismissing my points with your blind faith in some unnamed engineers doesn't help the rest of us understand if it's worthwhile, or to persuade anyone to part with their money.
The simple fact of the matter is the proposed gearbox swap will do nothing to achieve your primary goal of shortening the ratio of 2nd gear. I'm very sorry that that information had to come from me and not someone you'd consider an authority on these matters.
I'll leave you all to fantasise about gearboxes now. I've got an engine to fit.

Boom

Just one more thing to add, in the interests of posterity. I was incorrect about the MX5 2nd gear being 3% lower than that in the Jimny. It is in fact 3% higher. I feel its important that I correct that oversight as I don't want to spread inaccurate information.

All done. As you were Sniper!

Thanks for your input Busta..... hyperbole is a new word to me...

sniper

First proper meeting with Richard, the gaffer at the engineering firm and things are looking very promising.....

No need to machine a bell housing...... At first glance, a simple adaptor plate and an off-set flywheel with a spigot bearing will resolve attachment to the engine. It does mean that flywheels will need to be supplied for machining.

An existing off-set remote gear lever kit can be modified to place the gear lever exactly as needed. It's also a quick shift, not that they are needed in the mx box..... the throw is minuscule with it fitted. It does mean a short prop, the viscous coupling was dismissed.

CAD files are being examined next week and I should hopefully have a firm price by the end of next week. Pricing should be more advantageous with the proposed set up.

Whilst there.....

Custom coil over sets were discussed circa £250 per unit with damping and rebound adjustment.

4 pot callipers to suit the diesel vented disks, complete with mounts circa £500.....

Individual Throttle Bodies 40-45mm (dependent on tune) DCOE pattern at around £1100 as a complete kit.

I do have to order a batch quantity of 10 for the gearbox conversion but at the numbers intimated today, I may well take the liability myself and look to sell on as a complete kit for other owners.

sniper

Riccy, could you explain your reservations about a short prop.... Bit thick and don't understand why it may be an issue... Thanks.

sniper

Firstly - your earlier post...

I have some spare flywheels - one from each of 1.3, 1.6 and 1.8 (though the 1.6 and 1.8 are the same) in the garage you are welcome to if they are any use (and I can find them ).

Dont forget about the starter motor bolting through the gearbox bell housing, you need to start the car somehow, though I'm sure the engineering firm will know about that.

Coilovers and the brakes sound very interesting. Ive got a pair of vented diesel discs in the garage that are begging to go on with some decent calipers and the price is about half what ive seen before. Coilovers I'm thinking for the back as its got some basic stuff on at the moment and FOX are that price for second hand stuff

Now - Props. Some pics first...

This is a 'cush' drive unit:


(actually one from an Audi TT, but they are used on lard rovers too I think)

and a flange to flange scenario:



So the reservations about such a short space between the gearbox and transfer then:

-Short space to work and getting the box in there
-Vibration and noise very likely
-Movement from the engine and gearbox has limited options without twisting the transfer box about

The current mini-prop is about a foot long and has a slip yoke at the gearbox end that allows for about 10mm in or out, maybe a little more so getting the prop length right is critical to it working and articulating as you drive about.

The cush drive thing is a way of smoothing out torque through the drive train and helps quieten transmission noises and angles, but when worn feels like mega slop in the driveline or no drive at all. Viscous couplings must be some sort of fluid link like the rad fan?

It sounds like they think there will be enough space for a fairly conventional prop and I would trust their skills and judgement much more than mine

Having had the CAD files and a tape measure across my car, the results are a little mixed.....

Fitting to a standard transfer box in the standard position is too close.... Using an adapter rather than making a bell housing, pushes the box back just a touch too far.

An SJ transfer box will work..... Custom mounts are needed but when you consider that a cradle costs over £200, that's not so scary.

The cost of 10 conversion plates and the machining of 10 flywheels would be around £1100 so it is still a viable proposal for SJ transfer equipped Jimny's....

When I visited the showroom I was taken by an engine build set up that has my eye in a big way, more money but as there are no holiday plans next year...

Things have moved on some with existing plans and it looks like I will be fitting an R7ME gearbox with an SJ410 transfer box next month.....

The MX box will still be a possibility but will move to next year and could well be attached to a new power plant.

sniper