Murena high fifth gear

[Jon Weywadt]

I bought this kit to find out if the noise from my gearbox that I have since replacing the gears, are coming from the bush and spacer.
If this is the solution, then I try to make the other kit complete.
I always can sell it if it doesn't lead to a solution.

The kit arrived this morning. It was sold by "digitechdirectuk" on eBay, who sold the item as "new". I would rather say it was "unused", because it displays a bit of oxidization on the surfaces and on the side, that was not shown on the photo, one of the gears has several rust spots with appx. 1mm thick scales.  The teeth are ok though, so I expect no problems once the rust and oxidization has been cleared away.

[Oetker]

My set came in today.

There are some differences compared to the sets I bought some time ago.
If i jump to conclusions, the I think the gears will have a bit more distance from the groundplate as with the sets I bought before.
Maybe this month I find the time to try out.

Herman

[Jon Weywadt]

My set came in today.
---
Maybe this month I find the time to try out.

That looks exactly like my set. I am really happy to hear that the synchro fits perfectly.  That was a big concern of mine. 
Did you check the splines in the large gear wheel? are they identical to the Murena gear wheel?
What do you mean with the bushing not fitting? If that turns out to be the only problem I believe I can turn a new one that does fit. Fortunately that is the simplest part to make. 

[Oetker]

The splines looks the same.
I am not correct with the bush, you need it to fit the gear in the box.
I hope the inner diameter  of the bush fits the gearbox.
Looks promising.

[roy4matra]

On the newer type gearbox, the synchroring is the same, the rest I didn't fit to try out.

Well, I communicated with Roy bout this and though I am not 100% sure it will work...

Let me explain again as this thread has become so long, some have forgotten why the Citröen kit was available.

They had a problem with these units, and the work that was decided was necessary to improve the reliability, was to upgrade the end case bearings.  Since these bearings are wider, the end retaining plate is modified to hold them, and all the other appropriate parts had to be modified to match, so if the bearings are wider, some parts had to be narrower.  Citröen of course were replacing like for like with respect to the gears - 31:46 to 31:46.  We were taking advantage of the higher ratio and replacing 33:45 with 31:46 so the fork and casing had to be modified slightly to fit the larger gear.

So you can fit a complete kit and it will all fit correctly.

However, if you strip and take parts from a transaxle with the old smaller bearings, or you buy new parts that were for that version, then you will have to make sure you check all the parts are the same in the relevant dimensions so that they fit correctly.  You cannot 'mix and fit' or you will be asking for trouble.  As I have only fitted complete new kits to the later more reliable spec. I cannot verify what parts you would need for the older spec. so you must make sure yourself.

I hope this clear things up.

Roy

[Jon Weywadt]

On the newer type gearbox, the synchroring is the same, the rest I didn't fit to try out.

Well, I communicated with Roy bout this and though I am not 100% sure it will work...

Let me explain again as this thread has become so long, some have forgotten why the Citröen kit was available.

They had a problem with these units, and the work that was decided was necessary to improve the reliability, was to upgrade the end case bearings.  Since these bearings are wider, the end retaining plate is modified to hold them, and all the other appropriate parts had to be modified to match, so if the bearings are wider, some parts had to be narrower.  Citröen of course were replacing like for like with respect to the gears - 31:46 to 31:46.  We were taking advantage of the higher ratio and replacing 33:45 with 31:46 so the fork and casing had to be modified slightly to fit the larger gear.

So you can fit a complete kit and it will all fit correctly.

However, if you strip and take parts from a transaxle with the old smaller bearings, or you buy new parts that were for that version, then you will have to make sure you check all the parts are the same in the relevant dimensions so that they fit correctly.  You cannot 'mix and fit' or you will be asking for trouble.  As I have only fitted complete new kits to the later more reliable spec. I cannot verify what parts you would need for the older spec. so you must make sure yourself.

I hope this clear things up.

Roy

Thanks Roy for clearing that up. Since I was not planning on replacing the bearings, I will make sure that the width of the gear and bushing parts are the same as the originals. If the new gears are narrower, it should be possible to add shim rings to make up for the difference.

[Oetker]

quote Jon
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If the new gears are narrower, it should be possible to add shim rings to make up for the difference.
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That is exactly what they have done with the gearbox of JV.
Also this box is wining, but that is the older type gearbox witch have also extensive modifications to the fork.
We will see.

[JV]

Exactly.

Although as I remember Roy said that they have used both types of gearboxes together.

Would the Fiat kit have been better for my gearbox?

[Oetker]

Quote JV
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Would the Fiat kit have been better for my gearbox?
===================================

That is difficult to predict.
The older type gearbox was not suited to do the modification in the first place.
Lots of parts are different and at Car-joy I saw the differences when they were busy with the job.
I think you are the only one that has this mod in the world with this older type box.
Car-joy made extra spacers to make it work and changed the older type synchro to the newer type, and had some extra update work with the fork, because this didn't fit the switch gear.
Also youre box has a smaller groundplate.

[filip]

Anyone knows all gear ratios (numbers o teeths) in Murenas?

[roy4matra]

Anyone knows all gear ratios (numbers o teeths) in Murenas?

Yes I have all the info on this subject!  Email me directly roy@matraclub.org.uk as I don't get in here often.

Roy

[Jon Weywadt]

Now that I have the gear box apart, I will also replace the 5th gear with the new ratio set. But as Oetker's pictures show the gears are not formed the same.

I have set the gears side by side in the photo below, so you can see the differences.

The new gear with the synchro is 3,5 mm narower than the original, thus requiring a shim. The other gear wheel has a protrusion rather than a shallow indention. Therefore they cannot be fitted by just shimming. The shaft is not long enough and you would not be able to fasten the end nut. Besdes the end housing would not be deep enough to close as far as I can see.

The solution will be to take this gear wheel to a machine shop (or my friend Jan) to be milled down and turned to a shape identical to hte original wheel. Not impossible, but a rather annoying delay.

But who knows, perhaps I will have this done by the time I figure out how to replace the 2. gear synchro ring.   (see my Help needed topic on this matter)

[Oetker]

Sorry Jon, my plan to do the the box earlyer this year didn't match with some other plans, so you are on your own for now.
Also I have a spare box, and the sound in my old box is more and more less, so I'm not realy in a hurry to do the job.
In stead of doing the box on the car I am planning to do the spare box with the Fiat gears., and make that box in tiptop shape.
In this case I hope to learn from you, because this is moved to a winterproject now.
Keep us informed.

[JL]

Hi Jon

To machine these gears you might have to have them heat treated to soften them before they are worked on and then reharden them afterwards, some years ago I played around with Simca 1000 gearboxes and that was the only way we could machine the gears in those boxes.

Good luck.

Regards
John

[Jon Weywadt]

Hi Jon

To machine these gears you might have to have them heat treated to soften them before they are worked on and then reharden them afterwards, some years ago I played around with Simca 1000 gearboxes and that was the only way we could machine the gears in those boxes.

Good luck.

Regards
John

Yes, I thought about that, but I will try with diamond tipped cutting tools first. I would hate to not get them back to the corect hardness if I soften them up.