Trans or Spur Gear problems Looking for help

[smahoney1]

I recently installed a Castle Sidewinder 3 4600kv brushless combo with a SMC 2s lipo battery. I went through about half a charge when I started having problems. I would hit the throttle and nothing, just winding up. When I checked the motor, trans, etc. there were black shavings all over the spur gear. See photos in the attachment below. I took off the spur gear and inspected around and in the trans holes that I could see without taking anything apart. Everything looks ok besides the spur gear. I wiped everything down, reinstalled, and tightened the differential spring/nut all the way. I took a few passes and all seemed ok until a part of the steering assembly broke. Should I replace the spur gear and bearings in the spur gear? Any other parts I should consider replacing? What are the black shavings, is that from the old bearings?

https://www.dropbox.com/sh/l9e26gvro6ts0h3/AABPr8r9VbszKwglz6NqbBxya?dl=0

[jwscab]

That's a lot of motor on a 6 gear and the spur is melted around the diff balls. That diff was slipping quite a bit and overheated.

You'll need a new spur. Likely need diff balls and rings also.

[smahoney1]

Thanks for the reply. Should I search for a matching spur gear or switch to another tooth?

[jwscab]

depending on the current spur pinion ratio, you might want to run some calculations and see if there is a better ratio to run. at 4600kv I think that motor is something between a 10.5 and 9.5 turn motor. So look at gearing charts, and bear in mind the 6 gear trans internal ratio is 1.86.

honestly i would be really careful with that combo. you might end up wasting diff's continuously since there is no slipper.

[Lonestar]

that's a lot of motor to run on that poor 6G trans. You need a perfectly built diff to withstand this amount of modern power (even though it's mild by modern race motor standards). It could slip due to the absence of slipper, or just because it isn't built 100.00% properly.

What's that black grease residue on the spur? What did you grease it with? It won't solve your problem to use the right silicone lube, but if you use what I think you're using ie graphite grease on the balls, you will keep slipping and toasting the spur regardless of what mill you use.

Honestly, ball diff management is like voodoo... and if there's no slipper, it becomes disastrous pretty quickly.

rebuild the diff as per instructions with new parts and get a milder mill

[smahoney1]

Thanks for the tips. I'm not sure what grease was used when it was originally installed. I will work on replacing all of the parts with new per the instructions and go from there. What is 'milder mill'

[NomadRacer]

Thanks for the tips. I'm not sure what grease was used when it was originally installed. I will work on replacing all of the parts with new per the instructions and go from there. What is 'milder mill'

"milder mill" means a less powerful motor. Get you something like a brushless 17.5. The 6-gear transmission, with a properly built/set up diff. should be able to handle that (with the right spur/pinion).

[Lonestar]

Softer motor

[smahoney1]

Thanks again for the replies. Should I replace the spur gear with Team Associated #6634 81T and Team Associated #6626 1/8" differential balls?
Again I have a Castle Sidewinder 3 4600kv brushless combo.

[jwscab]

I'd get whatever gear combo is inexpensive and readily available, and get a few sets in one shot. you might consider getting some tires that have limited traction, this way the 'slip' will be at the wheels, hopefully preventing more meltdowns. Also tune back your esc/motor combo to give you a soft start.

[smahoney1]

Thanks. I ordered another set of wheels/tires and will tone down my esc for a softer takeoff.