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Here's how the gears turned out , firstly there is one small blemish , there's a swell in the width of the gear teeth and a slight narrowing either side , it doesn't seem to affect the mesh and its almost certainly because i angled the gears on the bed so i could fit them all in , so printing them flat should solve the problem , other than that they seem flawless however these were designed for FDM printing not resin and with FDM holes tend to print under size to you enlarge them by design knowing they will shrink in printing , i'm expecting all the axle holes to be too big but i don't have time this morning to check .The material feels very promising , i can flex the gears a little and this resin is meant to be "ABS like " , they honestly feel like a moulded part . The settings i changed were exposure time down to 6 seconds from 8 and much finer supports , both seem to have worked really well and the supports just peeled off in a very satisfying way leaving just a lightly dimpled finish .
Just after completion still hanging from the bed.

Straight from washing and removing from supports .

After final curing in the UV light box


Not too clear bit this is the defect from printing on an angle .

The Eiffel tower print reminded me of Alec Guiness in the lavender hill mob..

The gears fitted the 5mm axles better than i expected , in time i'll make them a tighter fit but for now they are good enough to test , i fitted them to one of my spare 3d printed yz-834b gearbox's and the mesh is good , better than i expected so I've built up the gearbox and installed it in the Yo-Clone-Oh , its pitch dark now but I'll test it tomorrow , not sure what to expect really but probably 2-3 min then failure

Well predictably the resin gears failed , i got 5 min out of them , the failure point was at the distorted section where it didn't mesh as closely , although there was damage to all the gears i think it was the debris from the first gear driven by the pinion that caused the damage further down the gear train , the first gear failed loosing nine teeth off its larger section and no damage to the smaller gear , the second lost only one tooth , third gear only a chip off one tooth and the diff gear lost an even smaller chip off just one tooth . this pattern of damage looks promising , if i reprint the gears flat rather than at an angle to the bed then the distortion should vanish giving a truer mesh and no weak point , ultimately i'm not expecting the first gear to survive and it may have to remain a CF nylon gear but i feel that there is a possible advantage for the other gears , the diff gear is hard to print cleanly in CF nylon and the second gear is awkward where the drive pin goes through to drive the chain , so i'll have another go .

New gears printed and fitted , once again its dark out so I'll wait till morning to strip the teeth off them I do have another resin coming to try as well .

Took about a minute to strip the first two gears so i rebuilt the box with just the diff and idler gear in resin and ran again with no holding back and got another 5 min before they failed , still no use at all but it was an interesting experiment , i have some Siraya Tech Blue engineering resin coming so i'll try again when it arrives , the cool thing about these Siraya Tech resins is you can mix them to change the properties so the fun will go on !

Good info, thanks for posting.
With how much power? What motor were you running when the gears failed?

It was running a 17.5 t BL sensored system with a 21 tooth pinion and 2s lipo on grass with high traction , pretty quick by vintage standards ,mild by modern standards , with a 27t stock vintage motor and ni-cad/ni-mh then they might surive a 5 min run or two ,maybe more ? I guess I should try it for due diligence but from printed parts I'm always looking for something I can abuse , I can use genuine parts if I baby them !

Okay, well that seems respectable. I thought maybe you were still running one of those cheap chinese brushed motors. 17.5 brushless is respectable power and running the car in grass will exert maximum loading on the gears.
I think you were wise to start with gears. I'd reckon that suspension arms and gears offer the greatest test for 3d printed parts. Find a material that survives as a printed arm or gear and you can use it everywhere else.

The new resin arrived this afternoon so i'm running a test print to check settings , this is a you tube channel CNC Kitchen (excellent channel) testing the blue resin and comparing it to 3d printed filaments . https://www.youtube.com/watch?v=Yjm7aRKISMI

Had my first print succeed with the new resin , this is Aria-the-dragon by Loubie off Thingiverse .

then i had a partial fail , all my own fault , apparently with resin printing its normal to manually place your own supports , i didn't know this and used auto supports , they were so dense they trapped resin between then and made a solid mess , i was able to sand it flat but its ugly on the bottom .

the other side is ok and i can still test then ok .

so its build the gearbox and test in the morning again , wish me luck !

When I tried to fit the gears only one was actually useable , the little one so its in there for testing , I have another set printing .

This thread is making me want to get a resin printer.

Me too!! Some great info, Dadio!

Right now for this hobby I think an FDM printer is still most useful but the big advances in resins are worth investigating , at least for me .