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turbo optima & turbo scorpion gearbox questions

turbo optima & turbo scorpion gearbox questions

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Old 07-27-2019, 08:14 PM
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Default turbo optima & turbo scorpion gearbox questions

im not sure where to begin with this, so hopefully it's coherent, and im thinking out loud here so this is probably going to be long winded.

im trying to put together an old kyosho outrage st. original gears are long out of production so i was hoping to put it together with gears from one of the rereleased kits. after studying the manuals on the kyosho website it looked like the turbo optima gears might work. so i ordered the necessary parts. diff set, diff shafts, spider gear set, diff case and pulley set, slipper parts, and a gear shaft. the good news is everything bolted together and fit in the original outrage gearbox case and motor plate. the problems started once i installed the spring and nut for the slipper clutch (which was NOT easy) the gearbox got really tight and the spring is almost fully compressed. (nut is level with the threads on the shaft as per the turbo optima manual). that's when the gearbox got really tight. everything seems like it's assembled properly. the only thing im questioning is how far out that top gear/slipper clutch are from the motor plate. so iv been studying the manuals online again and iv got a few questions.

on the turbo optima, how hard should it be to get the slipper clutch nut on? and how far away from the motor plate should that top gear be? as it is im going to have to shim out the middle/spur gear to make it fit and not contact the slipper plate.

on the turbo optima, the bushings/bearings that the shaft rids on. do those press in from the inside or outside of the gearbox case? after studying the manual more it looks like they go in from the inside (?). the bushings/bearings on the outrage st gearbox go in from the outside. so im thinking the slipper clutch spring is pinching the case half's together causing the tightness problem.
im thinking i may need the turbo scorpion top shaft, diff and final pinion gear. just not sure if they'll fit in the outrage st case. diameter of the diff gear is what i question. so does anybody know the diameter of the diff gear? or is there a turbo scorpion owner out there that measure the diameter for me?
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Old 08-05-2019, 07:14 PM
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alright, just an update. i went ahead and ordered the scorpion top shaft and diff and final pinion gears. the diff gear would work, it's the same gear as the optima, but the final pinion is to small and doesn't mesh with the diff. the top shaft is about a half inch to short. and with the slipper clutch on the gear side of the gearbox there is zero room for the spur gear. so even if the shaft were the proper length it still wouldn't work.
now for some good news. using the optima parts i think iv devised a way to keep the slipper spring tension on the shaft without transferring it to the gearbox case. im just going to need to switch from the plastic bushings to bearings, shave down the spacer between the back slipper plate and bearing. then shim in shaft on the inside of the gearbox from bearing to bearing to keep the slipper spring from compressing the gearbox case. this should keep any additional stress off the gearbox case and only put spring tension on center race of the bearing which will have no effect on the efficiency of the bearing.
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Old 08-19-2019, 08:44 PM
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another update. im making some good progress.
i think iv got a setup that will work. used all turbo optima parts.
slipper plates - KYOSC215
slipper pads - KYOSC216
gear shaft set - KYOOT225
gear set - KYOOT221
diff gear case and pulley - KYOOT208
inner diff parts - KYOOT222

this is my top shaft setup. i shaved down the sleeve by the slipper clutch, used an unmodified sleeve inside between the bearing and gear. then made the .090 long sleeve between the gear and bearing. what this set up does is uses the inner race of the bearing as a spacer. there is no side load on the bearings which means the slipper clutch isn't smashing the gearbox case half's together. the shaft assembly just floats in place. iv got about .005 endplay on the shaft.
if i had to do it over again i would probably cut out the flanges on the gearbox and use a 5x10 flanged bearing and install it from the inside. i think it would have been easier and might allow me to take the gearbox apart without having to remove the slipper clutch nut/spring/seat.


still working on the diff setup. gearbox case is molded to accept a 14mm OD bushing. the turbo optima uses a 10x15 bearing. so i would need a 10x14 bearing. i don't even know if a 10x14 bearing exists.
the original gearbox setup had a sleeve that went on the diff and a bushing that went into the gearbox, you just put grease between the sleeve and bushing. the optima diff doesn't need the sleeve it just fits into the original bushing. the diff gear is metal so i could just glue the original bushing in place to keep it from spinning and let the diff ride in that. however, the other half of the diff is plastic and the same size OD as the metal diff gear. so the sleeve won't fit and im not sure i want the plastic part spinning inside a metal bushing. i need to see if i can use the original plastic piece because then i can just use the original sleeve and bushing set up. i was really hoping to run bearings. ill tell more after i work on it and figure it out.
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Old 09-02-2019, 02:07 PM
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final update on this project.
i did what i didn't want to have to do, but sense i can't find a 10x14 bearing i was left with no choice. i used the original metal bushings for the diff. they were a bit of a sloppy fit so i shoe goo'ed them into the gearbox case to keep them from spinning and kept them removable for future replacement. so the diff is ridding in bushings. not the best way to go considering one side of the diff is plastic, but it was the only option i had. i went a little crazy with the associated black grease, that should keep it lubed up. i also had to shave down the diff cups a few thousandths. they had a 10mm od so they wouldn't slide through the 10mm id of the bushing. after shaving off about .003 they fit with no problems. to shave them i just chucked them into the drill press and took a file to them. but now the cups fit through the bushings with no issue. so assembly and disassembly of the gearbox is possible. after that everything went together no problem. so the trucks now a runner. iv run a couple packs and everything is functional and seems to be working properly. this is pretty cool, i haven't driven this truck sense 2000.
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Old 09-14-2019, 09:22 PM
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and now kyosho is rereleasing the 2wd ultima which is what the outrage st is based on. looking forward to seeing what they do with the gearbox case and rather or not it'll fit my truck. be nice if it would and they modified it so the diff would ride in bearings. based on the pictures the gears look like the ones i just bought. i think a lot of the suspension components should be interchangeable as well. maybe i can score a few replacements and maybe an upgrade or two.
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