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


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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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This are the dowels I made for the MX-5 gearbox.

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Sorry now for the simple quality of the next photos, my good camera in out for a repair.

This is the "center tool", 1" x 15 mm (TR crankshaft x MX-5 gearbox shaft)

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Next the adapter is on the TR dowels, fixed with 2 bolts, that's good enough for doing that

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the "center bar" is glued in with 2K glue and fixed for about 15 minutes

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the smaller dowel for the MX-5 box

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the bigger dowel for the MX-5 box

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another tool to get rid of the radial play of the MX-5 gear box shaft, which is noticeable (but standard)

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ready to move and bolt the adaptor on the MX-5 dowels

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the bolts I had to cut shorter, I fixed them with Loctite "strong"

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ready

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pull off the adapters from the MX-5 gear box and brake out the glued "center bar"

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all 3 adapters are ready

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final step, the red paint may give a owner in about 20 years (?) the idea not to open this bolts without serious reason,

if not - I can not help him

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well, that's it with the adapters, this was an interesting experience for me, I have to see what will be the next step

Ciao, Marco

Edited by Z320
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thank you Jochem,

sadly the next step is to destroy the MX-5 gearbox - for any further MX-5 use,

no way back from now, either it works on my TR or it will be for the scrap container

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More great work Marco - thanks for making this visible to us all !   i'm sure you'l find a creative way to make it work on the TR and avoid placing it in the scrap :)

cheers..... Andy

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11 hours ago, YOW500 said:

Yes, I agree Jochem.

Marco makes a difficult conversion look straightforward in the small steps which we see. A very nice piece of engineering.

Russell

+1 

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Hi, thanks to all.

Moving the gear shifter as far as possible forward seems to be to me the next challenge to look for.

I hope this works without opening the gearbox itself, cleaning it (seal on top is damaged) will be the first thing to do.

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Moving the gear shifter is possible on the NA (Mk1) gearbox, on the NB gearbox not.

Ciao, Marco

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7 hours ago, Z320 said:

Moving the gear shifter as far as possible forward seems to be to me the next challenge to look for.

what are the vertical lines depicting? To which does the gear shifter need to be moved forward?

It all seems a very exciting TV Show...the series finale is coming and everyone is awaiting the outcome....

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Good morning Marco.

I know we have spoken on e mail about your project. It may be of interest to others to see the Vitesse answer to moving the gear lever forward. For the TR2/3 cars the situation is very tight indeed. I do not have the tunnel details for your TR4/6, but I think the fit will be better.

I hope the picture can be seen !!!!!!!

Russell

IMG_0212.jpeg

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Hi Jochem,

you are my friend and you are very optimistic, but I cannot see the end of the story very soon.

I guess I passed 1/8 of the way. Here you see the challenge with the gear leaver.

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From the engine flange to the TR gb leaver it is about 585 mm , with the MX-5 gb with my adapter it is about 820 mm.

So I have to move it about 235 mm, but only 160 mm is possible by making the housing shorter, the rest you can see on Russell's photo.

 

Hi Russell,

thank you again for your photo, I also have to make this "extension",

this will move the ball on top of the leaver up and down when shifting, but this is no problem on the TR4-6 .

What I want to do is to get the end of the gb some [cm] down with the rear bracket, which I have to DIY anyway.

Ciao, Marco

 

Edited by Z320
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Hi Marco,

I see the chalkenge; can’t you make a thin (like 3 mm) adapter plate between the upper “selection thing” and the “tail end” of the main GB casing, and shorten the selector shaft(s)? Or am I simplistic?
Waldi

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If I understand you right / in other words:

I bolt off the selector housing (4 bolts), make it shorter,

also I make the selector shaft- (it is only one) and the tube shorter, than bolt it back with a offset adaptor plate.

That is my idea.

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Hi Marco, and Waldi.

I think all you can do is as Marco suggest. You will not notice the difference in the TR4/6 car from the cockpit. As Marco says, due to the need to off set gear lever forward when you push forward the top of the lever goes down, when you pull the lever back it will go up.

Russell

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Hi Marco.

Do you think there is ANY chance of moving the gear change lever mechanism further forward into the gear box itself?

If this is possible it would also fit the TR2/3 cars without the need to further modify the tunnel. As you know, the Mazda box is just a little higher than the TR3 tunnel at that point.

Russell

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Good morning Russell,

please look on the photo with the two gear boxes above.

You can see the top end of the shifter housing is much closer to the gear box shaft on the MX5 box than on the TR box: about 55 mm!

The reason for the needed modification of the tunnel must be another one.

Well: the crankshaft and gearbox shafts are all in one line and the unit is angled about 3° (if I remember right) in the cars frame.

The engine's oil sump is wedged to get a leveled ground - while the flange (to bolt on the engine) is falling with the engine.

I guess Vitesse had to lift the rear end of the gear box up for any reason, this must be visible by the not leveld ground of the engine's oil sump.

From the first fit I realized I have to modify "the bridge" crossing the TR4A frame where the rear end of the gear box is based.

This may be not possible the way it is needed to get the end of the gb down, the exhaust pipe could be the reason.

This is another issue far away on the horizon.

Ciao, Marco

Edited by Z320
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Hi,

I only only some cleaning this weekend (and some other work on the TR)

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While this Russell asked me (we are in good contact) if I see any possibility to move the shifter housing more forward, but I expect this does not work.

Reason: left and right on the end of the shifter housing the housing has "extensions" below the line where it is fixed on the gearbox.

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About 15.5 cm forward they will touch the front threads - and I expect I have to grind them off (arrow 1).

About 16.0 cm or more forward they I exect they will touch the gearbox housing (arrow 2) - I'm afraid I can not grind anything off there.

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Russell, sorry me for that - but we will see.

Ciao, Marco

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OK, opened from the top, left, right and behind,

I knew there is a roll pin and I was affraid it will be very bad to reach from behind - and indeed this is the case...

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Pushing it through is not possible, inside diameter is 3.5 mm, so my attempt will be to tap it M4 and pull it out.

Any other ideas are welcome?

Ciao, Marco

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Hi Marco.

Is the roll pin into a hole which does not go right through the shaft? or does the other side of the casting mean that you cant push it all the way through? If the hole does go right through, can you remove the tail of the gearbox, and  rotate the shaft to a position, so as to push the pin clear.

OR,  have you already pulled it out!!!!  LOL

Russell

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Hi Russell,

the roll pin goes through but it is out of reach from the left side,

from the cover there a spring is pressing a piston up angled 45 deg. up,

no way to get the roll pin out.

Ciao, Marco

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1 hour ago, Z320 said:

OK, opened from the top, left, right and behind,

I knew there is a roll pin and I was affraid it will be very bad to reach from behind - and indeed this is the case...

T3nFeLEWnkLze4En9fFqxXrCABOha3fCBq1ctVOi

Pushing it through is not possible, inside diameter is 3.5 mm, so my attempt will be to tap it M4 and pull it out.

Any other ideas are welcome?

Ciao, Marco

Hi Marco,

Tight access there,

I'd give it a go tapping a thread but beware breaking a tap as you do, it may be as hard as your tap. Failing that I'd drill it out increasing drill size until it collapses or gets thin on it's wall thickness (10-15 thou) and then try with a tap to "hook" into it enough to pull it out. Interesting.

Mick Richards

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