Nick Jones Posted November 21, 2020 Report Share Posted November 21, 2020 Hi Marco, Been following this with interest - some really great work happening in your workshop. Have one of my own going on - trying to get an MX5 NA 5 speed into a Mk3 GT6. Beginning to think I may succeed but there's a good reason (several in fact) why this isn't a common conversion! Thread on it here http://sideways-technologies.co.uk/forums/index.php?/topic/8925-mazda-gearboxes/#comments Cheers Nick Quote Link to post Share on other sites
Z320 Posted November 21, 2020 Author Report Share Posted November 21, 2020 (edited) Hi Nick, very impressive what you do and for different reasons we go slightly different ways: I have no milling machine, no W58 bell and I don't want to have this welded (TÜV). The MX5 gearbox is really an interesting alternative to the overdrive and I hope we both get the hole construction work. Ciao, Marco Edited November 22, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted November 22, 2020 Author Report Share Posted November 22, 2020 BTW: it is not possible to use a TR4A-TR6 flywheel on the GT6? Quote Link to post Share on other sites
Z320 Posted November 23, 2020 Author Report Share Posted November 23, 2020 Hi, me and my wife had a 50 miles test drive yesterday with the new and downwards twisted starter on the TR. I touched it 2 times and it had never any special temperature. OK, it was 5°C cold outside; I will keep an eye on it. Yesterday I ordered a sintered bronze bush and started to make the adapter for it on the lathe. Ciao, Marco Quote Link to post Share on other sites
Nick Jones Posted November 23, 2020 Report Share Posted November 23, 2020 On 11/21/2020 at 10:58 PM, Z320 said: Hi Nick, very impressive what you do and for different reasons we go slightly different ways: I have no milling machine, no W58 bell and I don't want to have this welded (TÜV). The MX5 gearbox is really an interesting alternative to the overdrive and I hope we both get the hole construction work. Ciao, Marco Thanks Marco. Just to be clear, all references to the W58 in my thread are a red herring, a side-trip. No Toyota parts at all are used in the conversion that I'm doing now. The bell housing I'm using is actually from a Triumph 2000/2500 BW35 autobox. The W58 link is that I have had one fitted in my Vitesse since 2007, so I know it is possible (though not easy) to put one in a GT6. I have a spare W58 and also a very unusual bell housing with the starter housing on the right side, that I bought used from the US after I converted my Vitesse (which used a cut 'n shut bellhousing). So I was looking to see how difficult it would be to use that bell housing and make a new back-plate to match it to the engine. In the end I decided to use the MX box - mainly because I bought 3 for less than £100 and one W58 costs more like £ 1000 these days! For the GT6 and Vitesse the motivation is not just for the extra gear, but also to get a gearbox that doesn't break or just wear out every 40k. The original gearbox is very weak, unlike the TR one which is reasonably strong. I quite pleased with the way mine is progressing, but I still have to fabricate a rear mounting, which will be very hard due to the limited space, and also choose and install a concentric clutch slave. The gear selection is also presenting a challenge...... I can select all 6 gears (5+R) really easily..... but it needs to be much harder to select reverse directly from 5th! Would have been easier to take the route you wisely chose, move the original selector box as far forward as possible and modify the tunnel cover to suit. Cheers Nick Quote Link to post Share on other sites
Z320 Posted November 23, 2020 Author Report Share Posted November 23, 2020 The concentric clutch slave is also my next chapter, but because I did that already for my TR gb I expect no problem. I use a Sachs unit again from the Opel / Vauxhall Omega for about 50 Euro. Quote Link to post Share on other sites
Nick Jones Posted November 24, 2020 Report Share Posted November 24, 2020 Thanks for the information on the Clutch Slave. Do you know what the release bearing contact diameter is on that? I have previously been advised to consider the Corsa/Astra part. Older Mondeo and Saab are also possibilities. Was going to get some used examples from a scrapyard to work with. Obviously I will use new (and decent quality) for the final assembly! Nick Quote Link to post Share on other sites
Z320 Posted November 25, 2020 Author Report Share Posted November 25, 2020 (edited) Hi Nick, I ordered the Sachs unit yesterday, please wait. Do you know my post about how to modify it for TR use? It is anywhere out there on the big heap of "general technik". And another one about the limitation of travel of the master cylinder. This is also on the big heap of what ever forum.... Ciao, Marco Edited November 25, 2020 by Z320 Quote Link to post Share on other sites
Nick Jones Posted November 25, 2020 Report Share Posted November 25, 2020 7 hours ago, Z320 said: Hi Nick, I ordered the Sachs unit yesterday, please wait. Do you know my post about how to modify it for TR use? It is anywhere out there on the big heap of "general technik". And another one about the limitation of travel of the master cylinder. This is also on the big heap of what ever forum.... Ciao, Marco Thanks. I'll have a look around. I'm aware that care is needed with total stroke. I'll fit a smaller master cylinder if necessary - and a pedal stop if I really have to. Nick Quote Link to post Share on other sites
Z320 Posted November 26, 2020 Author Report Share Posted November 26, 2020 (edited) Hi, first I wanted to make the spigot bush from a solid bar of bronze, finally I ordered a bush made of sintered bronze to let it soak with gun oil. It fits in a steel adapter with a interference fit, the steel adapter also with a interference fit in the crankshaft, reaching through the flywheel. Countersunk to get the spigot easily in The rear end is drilled through with a M10 thread inside to push the unit out without problems if needed. If I ever need and remember or the next owner realizes this.... Ciao, Marco Edited November 26, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted November 27, 2020 Author Report Share Posted November 27, 2020 (edited) Hi, the Sachs / ZF unit is in, lovely german quality....made in China. I send only Nick some photos because they are not interesting for all / for the story. It will be a challenge to fit it because the MX5 has a very short release bearing, much shorter than the Sachs unit. And there is no space wasted by a bearing carrier like on the TRs. A shorter one would be interesting, perhaps Roger will tell us about his Saab unit... Ciao, Marco Edited November 28, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted November 28, 2020 Author Report Share Posted November 28, 2020 (edited) Hi, before I continue I want to tell you all about the friction plate. The splines inside have to fit the MX-5 gearbox shaft (24 mm x 20 tooth), the friction lining must be about d= 216/152 mm to fit the TR flywheel and clutch cover. Sadly the clutch friction plate from the 1.6 l MX-5 is d = 200 mm = too small, from the 1.8 l MX-5 it is d = 225 mm = too big. So I wanted to order the one from the 1.8 l and modify it, but with some Google search I found a 100% suitabe. Why ever AISIN's friction plate DZ-008 is for other Mazda models - but they offer it for the 1.8 l MX-5 too, it is d = 215 / 150 mm and fits perfect, 51.16 Euro and it was mine. Ciao, Marco Edited November 29, 2020 by Z320 Quote Link to post Share on other sites
roy53 Posted November 29, 2020 Report Share Posted November 29, 2020 Thats good one part that you do not need to modify. The release bearing looks like a challenge though. Roy Quote Link to post Share on other sites
Z320 Posted November 29, 2020 Author Report Share Posted November 29, 2020 Yeah, indeed you are right, sadly this is perhaps the ONLY part that needs no modification, but I hope for another one Quote Link to post Share on other sites
Z320 Posted November 30, 2020 Author Report Share Posted November 30, 2020 (edited) Today I did some calculations... How much can I compress the Sachs unit max (gaiter is off)? aluminium cap is from my older release bearing project.. 23 mm, minus about 6 mm for abrasion from the friction plate over the years = 17 mm But how much can I compress it without the cylinder touching the splines? 17 mm, minus 2 or 3 mm gap to the splines = 14 mm How deep do the "fingers" of the clutch cover reach in the bearbox bell housing? 100 mm - 29 mm = 71 mm How long is the Sachs unit from the point of the flange which I want not to touch? 81,5 mm....Can I reduce the length by modifying the platform? Yes How deep can I go in the gearbox bell? 135 mm. Do I get this fitted? Yes. Who can tell me how many millimeters I have to make the platform of the Sachs unit shorter? Ciao, Marco Edited December 2, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted December 5, 2020 Author Report Share Posted December 5, 2020 (edited) Hi, the result is 3.5 mm, it is now about 9.3 mm, finally it has to be 6.3 mm. I want to bear it on the cover where I marked it black with a permanent marker. Sadly its inside diamater is about 5 mm too wide So I started to make a new one from a circular blank of 5 mm steel. The set-off is a about 1 mm and is needed to compress the seal of the hydraulic unit, this flange is a part of the housing and not only to fix the unit. Ciao, Marco Edited December 5, 2020 by Z320 Quote Link to post Share on other sites
Nick Jones Posted December 6, 2020 Report Share Posted December 6, 2020 Watching with interest...... getting close to this point myself. Why make a whole new plate rather than just opening out the hole in the one supplied? On 11/22/2020 at 7:40 AM, Z320 said: BTW: it is not possible to use a TR4A-TR6 flywheel on the GT6? I never answered this. Seems that the TR4/4A flywheel diameter must be smaller than the ones for the 6 cylinder engine. I'm pretty certain the TR5/6 flywheel is the same diameter as the GT6/Vitesse and 2000/2500 range (though thicknesses and weights vary considerably across the models) and there is no way that the GT6 flywheel fits in the MX5 bell housing. As the 6 cylinder has a removable steel adapter plate as standard my initial plan was to make a new backplate to suit, but to make that work I'd need to modify the flywheel to take an MX5 ring gear, and that (I think) means the clutch would no longer fit. In hindsight it might have been easier to have a flywheel made and use the MX clutch! Nick Quote Link to post Share on other sites
Z320 Posted December 6, 2020 Author Report Share Posted December 6, 2020 (edited) 23 minutes ago, Nick Jones said: Watching with interest...... getting close to this point myself. Why make a whole new plate rather than just opening out the hole in the one supplied? I never answered this. Seems that the TR4/4A flywheel diameter must be smaller than the ones for the 6 cylinder engine. I'm pretty certain the TR5/6 flywheel is the same diameter as the GT6/Vitesse and 2000/2500 range (though thicknesses and weights vary considerably across the models) and there is no way that the GT6 flywheel fits in the MX5 bell housing. As the 6 cylinder has a removable steel adapter plate as standard my initial plan was to make a new backplate to suit, but to make that work I'd need to modify the flywheel to take an MX5 ring gear, and that (I think) means the clutch would no longer fit. In hindsight it might have been easier to have a flywheel made and use the MX clutch! Nick Hi Nick, sorry, no way, the hole in the supplied ali plate is too big and not to small... I never asked myself seriously but I have no doubt: the fly wheel on all TR2 to TR6 have the same diameter, so I wonder why the GT6 is differnt...? Indeed the flywheel of the TRs do not fit in the MX-5 gearbox bell, but it does with the MX-5 gb 10 mm backwards by my adapter ring. Ciao, Marco Edited December 6, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted December 6, 2020 Author Report Share Posted December 6, 2020 (edited) Well, time today to answer a question which nobody ever asked here, but I did myself and expected a YES - hopefully: are the splines of the clutch friction plate in contact the full length with the splines of the gearbox shaft? The splines of the MX-5 gb shaft start about 35 mm in the gearbox bell.... they are about 30 mm long and end about 65 mm in the gearbox bell housing. This is where my reference bar is, 100 mm deep in the gearbox bell housing. Next I go the other way, from my "100 mm reference bar" back (out): the splines of the friction plate start 100-45 = 55 mm in the MX-5 gb bell housing.... and about 20 mm deep they end 100-65 = 35 mm deep in the gb bell housing. So the answer is: they are exactly the full length in contact with each other. This is more fortune than my plan, I decided for me it would be OK with only 15 mm of 20 in contact. The constructions of TR and Mx-5 seems not to be so much diffreent: with my adapter ring I pull the friction plate 10 mm out of the gb and the MX-5 flywheel probably is 5 mm less solid... With the Sachs unit also everything goes well together, so Fortuna seems to be on my side? Ciao, Marco Edited December 7, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted December 7, 2020 Author Report Share Posted December 7, 2020 (edited) Hi Nick, I just checked this for you: the outside diameter of the TR4A starter ring gear is about 291 mm, from ordering the high torque starter I know they are interchangeable on all TRs (with some differences about fixing and tooth). So I guess the TR flywheels all have the same diameter. Maybe others here can confirm this. Ciao, Marco Edited December 7, 2020 by Z320 My bad English Quote Link to post Share on other sites
Z320 Posted December 8, 2020 Author Report Share Posted December 8, 2020 Today I took the cover off, its a lightweight part, inside a shim for the bearing, the paper seal is OK, I will use it again Sorry, my hacksaw.... To keep the lipseal in the cover and to fix it on the lathe I use my DIY face plate in the lathe's chuck. Fixing and centering was more simple to do than I expected with the centering plug above (about 2 minutes). To continue tomorrow... Ciao, Marco Quote Link to post Share on other sites
Z320 Posted December 9, 2020 Author Report Share Posted December 9, 2020 Ready, I had to reduce the diameter of the shaft for about 0.3 mm and make a "platform" for the circular steel plate. It was not needed to make the "cylinder" shorter. I'm pleased with the result Quote Link to post Share on other sites
Ian Vincent Posted December 10, 2020 Report Share Posted December 10, 2020 A lovely piece of work Marco. Rgds Ian Quote Link to post Share on other sites
Z320 Posted December 11, 2020 Author Report Share Posted December 11, 2020 Hi ian, thank you very much! Well, I told you the cover is a lightway construction, it is not made for to bear the forces of the clutch, and this is about 120 kg with the B+B (ap) clutch cover! Perhaps it stands the forces, perhaps not, so I decided to do some more effort to avoid any deformation. I leveled the top of the 4 screws around the steel plate and liftet their heads with individual washers (2.7 - 3.2 mm) made of brass. A closer look This will be solid enough! Tomorrow I will fit it on the gb and have to determine the point where I have to bore it for the only point here I will fix the unit. Ciao, Marco Quote Link to post Share on other sites
Z320 Posted December 12, 2020 Author Report Share Posted December 12, 2020 Ready, the Sachs unit is in position. A last time I check the pre compression by the clutch cover. 58 mm - 71 mm = -13 mm = that's LOVELY! Next I have only to do and modifiy about.......25 other details , so the project will be pretty soon finished. I hope this is not an endless and boring story to you, if it is, please be gentle with me. Ciao, Marco Quote Link to post Share on other sites
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