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my new gearbox? (Mazda MX-5 to TR)


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Hi Nick,

highly respect from me, to fit the MX-5 gearbox to a GT6 is much more challenge

 than to fit it to a TR (flywheel, speedo drive, switches, shifter box).

And a milling machine  is needed, which is not the case for a TR and which I don’t own.

Allow me two questions (sorry me if you have written it anywhere):

- the MX-5 shifter shaft you seal with a lip seal or not?

- your shifter box is not sealed and so the lubrication is by grease?

Regards, Marco

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Ups, the adaptors are already delivered, I'm really surprised about the laser cut surface! Tomorrow will be first fit, please keep fingers crossed for me.  

Thanks Russell and Andi, thank you very much, all worked well, fit was 100% on first attempt, the 8 mm drills are exaxtly to the point they have to be for the 5/16" bolts! Btw, the bar is on

Talking of gearbox changes, back in the 8o`s when I was involved with Jaguar racing we converted a V12 XJS from a GM 400 auto box to a Cosworth T6 manual 5 speed by a cut and shut of the two bell hous

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11 hours ago, Z320 said:

- the MX-5 shifter shaft you seal with a lip seal or not?

Yes it is.  This is complicated by two things (or even three). 
Firstly the shaft has two chunks machined from it to activate the neutral switch and one of these is right in the zone that the seal needs to work.  So I had to buy a length of 14mm silver steel, free the original selector finger from the original shaft (machine the weld off in the lathe), turn a step in the new rod and re-weld.  Not difficult, just yet another step.

Secondly, the bore that seems purpose made for the seal (it kin-of is, it's where the OE tube seal goes) is an odd size @ 20.5mm.  So a 20mm seal falls straight in... and out.  A 21mm seal (less common!) is really tight.  I managed to get it in without killing it - and it seems to work. 

The "maybe"

third thing is that the seal I've used is really intended for a rotating shaft, but is having to deal mainly with a sliding motion.  There are special seals for that, though not in 21mm OD that I could find. Some say just remove the garter spring from the rotating seal, some say it'll be fine, don't worry.  We shall see!

12 hours ago, Z320 said:

your shifter box is not sealed and so the lubrication is by grease?

Pretty much.  There are three parts to this.
Firstly the additional bearing block to support the outer end of the shaft.  This has an oilite bush in it, and some grease, with an oil seal at the front and a closing plug at the back.  The closing plug has a small breather hole in it.

Secondly, the shift lever balls.  Oil lubricated in the OE design - at least until the little gaiter fails (which they all do).  The upper main pivot ball rides on spring loaded nylon cups.  I've lubed them with moly grease.  The smaller ball on the end of the lever has a snap-fit nylon cup on it which would run nearly for ever, even dry, but the outside of the cup rides up and down a few mm in the gate block, so I've moly greased that too.

Thirdly, the gate plunger.

IMG_5608s.jpg.7db3acbbba97c242437cc795c64dfad3.jpg

It's the the thing the red arrow is pointing at, and its exactly the same Renault part as the one under the green arrow (which is supposed to make it harder to select reverse when you didn't mean to).  It is basically a 10mm ball bearing on the end of spring loaded plunger. 

IMG_5371s.jpg.a4fe473e752d625a289348ed915f499e.jpg

This ball runs on a number of little ball bearings inside the plunger and is intended to be oil lubed.  It's greased now.....  I thought about drilling and tapping it's cap for a grease nipple but didn't actually do it.

IMG_5596s.jpg.4c9ea9eba9390a7be7d2ebdf4d8fe76f.jpg

and it acts against this V block.  The bottom of the V is the 3-4 gate so the plunger pressure tends to try and return here, giving the centering action.  You can see the pattern the ball has left working through the shift pattern.  The raised area is where reverse is.  It's meant to define it and make it harder to get by mistake....  The hole at the back is where the cup on the end of the shifter lever goes.

Hope this gives some idea of how things work - seems I didn't really take quite the right pictures for this.

As for the lubrication, I'd prefer an oil bath but really not practical.  Hopefully the basic design is simple and robust enough to survive.  The roller plunger is perhaps the most vulnerable - we shall see.....  Testing has started....

Thanks for the kind remarks.

 

Nick

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Posted (edited)

Hi Nick,

thank you to explain, you had much more a challenge to solve then I had to solve and you did it very well!

Allow me to show your TR mates what you are explaining about the spring leaded pivot ball and the nylon bearing and snap-in cap.

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Actually I'm waiting for Russel asking for the possibility to get the original shifter housing 80 mm more forward... :lol:

This evening I took a scale, marker and my camera to examine this before he asks, the red arrow shows the final point for a cut.

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This way the gearbox body has to be cut out, loosing the reverse light switch and welding the housing in the gearbox body?

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A view from the other side

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Moving the selecter housing 70 - 75 mm the flange of the 5st/R gear plunger will touch the gearbox housing?

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Possible or not? Russel, are you ready for an experiment?

Ciao, Marco

Edited by Z320
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Hi Marco.

Firstly. I have to say that you and Nick have completed two very detailed projects, all credit to you both.

Secondly, Marco, does 'an experiment' mean that I have to cut the top of my expensive Vitesse gearbox? LOL

Russell

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Sorry me, Russel, not at all you have to touch your Vitesse gearbox.

But you asked me that question, you have the skills and worksop - and as I know - an untouched MX-5 gearbox?

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18 hours ago, Z320 said:

Allow me to show your TR mates what you are explaining about the spring leaded pivot ball and the nylon bearing and snap-in cap.

Thanks! :)

Hmm, this was one method I looked at.  I think you'd need to extend the shaft rearwards and add another bush to provide enough shaft support.  You'd also need to find a way to jig it in position securely for welding.  Would produce a nice result though.

You need to get hold of a cheap used NA 'box and take the rear casing off it Russell.  This is actually where Vitesse get theirs from for the TR conversions as the NC box tail housing is not amenable to moving the shift.  I understand they have a "universal" rear casing in the works, but I'm not sure how far along it is.

Nick

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Posted (edited)
1 hour ago, Nick Jones said:

I think you'd need to extend the shaft rearwards and add another bush to provide enough shaft support.

Nick, you are absolutely right. This could be made of bronze and glued in the housing after drilled trough.

Some kind like this, only bigger and with a - for example - 6 mm oil return and breather pipe uo and in on a higher level of the shifter housing.

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1 hour ago, Nick Jones said:

You'd also need to find a way to jig it in position securely for welding.  Would produce a nice result though.

Yes, with the tail off you can bolt a bar with a 14 mm drilling on it and need a pivot piece at the rear,

than you can slide the shifter housing, file the gearbox casting and weld all together. Some kind like that..

LL5ELf0AzEtrIrcxVQuOH_caAUoXRWpBzf_ZBasO

WE GOT IT! Now we simply have to find someone who does the job. If you - unknown talent - can read this you are our man!

Ciao, Marco :lol:

 

Edited by Z320
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Posted (edited)

todays status:

gearbox crane modified, brackets browned and oiled (black oxide), what I did the fist time and is the suitable design

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speedo drive housing closed, all bolts cut to the correct length

4d6C_85l6Fz5AiSVEdJ-S9YC4hpfmnzAI0sPP_VP

Last is to brown the adapter ring and....make a brake until TÜV im May.

Ciao, Marco

Edited by Z320
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  • 2 weeks later...
Posted (edited)

Hi there,

today I got a "love letter" from TNT / FEDeX with news about my probshaft:

import VAT + custom tax + paper service......102,52 Euro! While the probshaft was only about 260 Euro.

@&%$§!!?@ Allow me to tell the Bexiteers among you, I'm convinced about: Der Schuss geht nach hinten los!

Today I made the gear shifter, slightly tapered, aluminum

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I "only" have to bend it

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Even with Mahagoni it did not work in my hydraulic press, the Mahagoni from above was too soft

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This way it worked, the aluminium wrapped with painter tape to protect the surface

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4etrK3BSUJqRbeCX5Na9Xc3sIIvBwMivoXhpOdB5

Shifting the gears works LOVELY, I'm VERY pleased about, specially the reverse will please my wife!

Later in the afternoon I browned the adapter plate to give it a classic look (sorry, no photo).

Ciao, Marco

 

Edited by Z320
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Yeah, and I've very excited about.

This is a photo from the browned adaper plate, I did not want to have it zinc coated, alternative would be simply oil it.

nodrxyebq-JB7SZHughhNk9YZ2YAnXMhgNVnSMOO

This is a chemical reaction made with an acid, finally stabilised with oil.

I tell you the truth: I'm a bit in doubt using it, but I used a brush (recommended by the producer) to limit the need of the acid.

The result is "OK", it could be better if I would have been more accurate in removing all oil.

Ciao, Marco

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13 hours ago, Z320 said:

...especially the reverse will please my wife!

 

a bit of tasteful humour, at last

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14 hours ago, Z320 said:

Today I got a "love letter" from TNT / FEDeX with news about my probshaft:

import VAT + custom tax + paper service......102,52 Euro! While the probshaft was only about 260 Euro.

@&%$§!!?@ Allow me to tell the Bexiteers among you, I'm convinced about: Der Schuss geht nach hinten los!

"Der Schuss geht nach hinten los!" indeed!  Lots of them - many partially disguised by covid chaos at present.

TNT/FedEx are bandits and thieves. They are brazenly exploiting the confusion caused by brexit. You should be paying VAT only.

My company has been using them in the other direction to import our product from Germany - but no more. We recently got our “bill” for January of >£40k. This is 10X “normal”. Also a £60k bill for “VAT”, which is completely incorrect.  They have also been trying to extract money direct from our customers where things were shipped direct, which is also incorrect (though partly the fault of our parent company). They refuse to engage with us at all, presumably because they know full well they are in the wrong. They are going to have to engage to get any money........ They’ve lost our business for ever.

Gear lever looks great. With look “factory” from inside the car.   I am very curious - is it possible to select reverse directly from 5th gear?  Or do you have to allow the lever to return to the centre of the gate first?  My tests with used NA boxes are inconclusive - on some you can select direct (the well worn ones?) and some not.  On NB boxes, with all I have tried you have to return to the centre of the gate before reverse can be selected.

Have you considered the extra range of movement that the rubber gaiter will need to accommodate compared to standard? Got some slight problems with mine as the pivot point is 25mm lower than standard so the amount of motion at the gaiter is increased to the  limit of its abilities. Not sure what the TR gaiter looks like....

Cheers

Nick

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Posted (edited)

Hi Nick,

the charge from FedEx is "only" € 35,33, a receipt from the customs Köln is added with € 68,30....

About to shift in reverse a clear NES, I can / can't shift directly from 5 to R.

A pin in the housing (right, lower arrow) and a "wing" on the "shifter block" (left, upper arrow) are responsable.

  ZkPqGIB3pb8PRuSVcWTsi2Aw94UMECAZl3xTv9x9

On the photo you see gear #1 is in: lever to the front-left, "shifer block" canted right and slided back.

Gear #5 the shifter block is canted left and also slided back. Moving the lever from 5 to N the "wing" hits the pin and you don't get to R because of that.

To shift to R you have the press  the lever stronger to the right (againt a sping loeaded plunger) to cant the "shifter block" more to the left - this way the "wing" moves to a lower position than the pin.

Now the wing can pass the pin and you can slide to R.

If the wing is strongly worn, AND the pin (silver steel) maybe too,

AND you a bit clumsy by purpose AND a bit too much right with the lever AND pull the lever powerful,

it could be possible the "wing" passes below the pin and you compress the spring in the plunger by pulling the worn wing like a wedge forward.

But by moving from 5 to R the spring loaded plunger will press the lever to the N position between 2 and 3.

I hope this explains...

Yes, I expect to cut out the gaiter (two parts on TRs) because the rear end of the horizontal bar is already higher than the gaiter, I will see.

Ciao, Marco

Edited by Z320
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5 hours ago, roy53 said:

it looks like you must be getting near to testing it.  No pressure.

Roy

I'm counting down the days

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Posted (edited)

Hi,

another preparation today before fittig the gearbox was to lower the engine as much als possible.

Because I expect the adapter and the top of the MX-5 gearbox will touch the gearbox tunnel.

left

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right

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After all (sorry, no photos), this is another @§$"!!&%?@ story, I'm about 5 mm lower.

Ciao, Marco

Edited by Z320
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On 4/17/2021 at 6:31 PM, Z320 said:

Hi,

another preparation today before fittig the gearbox was to lower the engine as much als possible.

Because I expect the adapter and the top of the MX-5 gearbox will touch the gearbox tunnel.

left

gdf_uAr1hWEdO5j8bR-wP42H68pu-gfdVfPE4Dpt

right

jR2YicW_Pr0CwosHamsOCsB3VigmrfDEFN833xId

After all (sorry, no phozos), this is another @§$"!!&%?@ story, I'm about 5 mm lower.

Ciao, Marco

Interesting throttle link bar there Marco, definitely not original and strange seam around where the flange for the gearbox cover is.

Stuart.

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Hi Stuart,

thank you for watching and ask.

I made the connector because the shaft was twisted and I was not able to give full trottle.

This was the simplest way for me to adjust it instead of twisting it back with several try and error.

The grey seam is quite interesting!

This is the end of gearbox cover, on my TR4A was always slided under the tin metall strap which is welded there on the bulkhead.

In pieces again I want to try to fit it on top of it. Is this the way to install it correctly - inside on top?

Ciao, Marco

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1 hour ago, Z320 said:

This is the end of gearbox cover, on my TR4A was always slided under the tin metall strap which is welded there on the bulkhead.

In pieces again I want to try to fit it on top of it. Is this the way to install it correctly - inside on top?

Ciao, Marco

Yes the cover should sit over the return on the bulkhead and there should be captive nuts in cages that slip over that lip to affix it to, Im surprised you could get it to fit under the lip anyway, fitted over the top of that lip would give you a bit more clearance to the bell housing also https://www.moss-europe.co.uk/fitting-kit-gearbox-tunnel-cover-713569fk.html

Stuart.

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2 hours ago, stuart said:

Im surprised you could get it to fit under the lip anyway.

Stuart.

I found it this way with a "sponge seal" between, this is a lovely tight fit!

Screws I only use the ones to the floor. But indeed the both front edges to the must be cut off.

I will have a closer look on that and will put the cover there from above!

Thanks again, Marco

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47 minutes ago, Z320 said:

I found it this way with a "sponge seal" between, this is a lovely tight fit!

Screws I only use the ones to the floor. But indeed the both front edges to the must be cut off.

I will have a closer look on that and will put the cover there from above!

Thanks again, Marco

You can see the cage nuts on their clips here in this picture of a TR5 with the cover removed and the box out of the way.

Stuart.

 

073 - Copy.JPG

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Posted (edited)

I can imagine it is a lovely job to get the screws in there!

This is why I was pleased to slip it below that lip.

Edited by Z320
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