Replace RC10GT ball diff with gear diff?

[cobrakai]

I'm not sure silicone paste is going to help you and lead to further frustration. The proper diff lubes aren't super slippery and actually allow the steel balls to bite into the rings. Too slippery of lube and they just slip and slide creating heat which damages everything in the long run.

As an example AE have two different silicone diff lubes, a standard silicone lube for pan cars (red writing), and their stealth lube (black writing) for everything else. If you use the standard/pan car silicone grease in any of the stealth diffs they will slip and destroy themselves.

I made that mistake once - I used a moly fortified grease in the diff gear. Even when FULLY tightened down, the car wouldn't go anywhere. That stuff is slippery as hell.

I am pretty sure the two greases that AE uses - the clear and the black, are silicone grease and an additive lithium grease (likely with 3% moly). Since I switched back to silicone and got all the old stuff out of there, I haven't had a slipping issue, but I still have crunchy balls hehe. After researching here it makes sense that the diff balls are flat spotted from the slipping.

[RC10th]

Diff balls last a really long time and rarely need replacing. it's usually the thrust bearing that causes a crunchy diff. It's a good idea to replace everything if you've had problems before. Another key point is to make sure when you put it in the diff case that the diff bolt is on the correct side, if it's wrong it could loosen and you guessed it, slip and destroy. lol

Here are the three greases AE make or repackage. The standard silicone grease will kill a diff.

[jwscab]

The associated silicone lube looks suspiciously like the silicone lube you use for plumbing fixtures and rubber washers.

I also dont think it matters what side the diff screw is on. Except for maybe oval racing.

[cobrakai]

So, a little update guys.

I rebuilt the diff with factory parts. I went with Acer carbide diff balls, sanded the diff rings, and sparingly used grease. The diff was BUTTER smooth after assembly. I broke it in according to directions I found online, and slowly increased the screw tension.

However, even when fully locked down (I know you should never fully tighten it), the diff still slips on full throttle on asphalt. I can hear it chirp/bark. If I have the slipper loose at all, it just slips way too easily. This setup was clearly not designed for the torque of a brushless motor... versus the smooth clutched nitro power.

Anyway, not really sure where to go from here. Right now I have the diff fully locked down just so it can put the power down, but it's only a matter of time before the tensioning screw breaks, and it certainly doesn't handle as well as it could considering it's so tight.

I'm looking at doing a gear diff swap again. It looks like the SC10 gear diff is the closest thing dimensionally, the narrowest, has 52 teeth, and metal gears. Since I'm going to have to do some custom fabrication (probably?), would you recommend anything else instead? I'd like to fully bulletproof it so I don't have to take the diff apart anymore except for routine maintenance.

[jwscab]

Upgrade to a b4.x clutch. Gear up your spur/pinion to knock out some torque. You should have no issues even with good traction.

[cobrakai]

Upgrade to a b4.x clutch. Gear up your spur/pinion to knock out some torque. You should have no issues even with good traction.

Looks like it has a lot more surface area. Could be a worthwhile upgrade to actually get some adjustment range on the slipper... The pinion is already pretty tall. I haven't even been able to top it out yet as that would mean over 60mph.

[jwscab]

right, the later clutch has two discs, and a better adjustment range. your 3900kV motor is probably more like a 13t brushed motor so the recommended chart for the RC10T2(same internal trans ratio) for a 13t motor is 87/17 spur/pinion. not sure how far you are off from there, but it might be worthwhile to try it if you are really far off.

I'm running a 4600kV on a carpet setup(good traction) on an old stealth trans with stock slipper with no real issues, so you should be able to solve this.

the b4 clutch requires the b4 topshaft, just FYR. if you can find a takeoff clutch setup from a b4 or t4 (even b/t5 maybe?) usually there are guys parting stuff on ebay.

[cobrakai]

I've got a 21/66 pinion/spur. Right now it can be cruising along about 20mph and if I punch it it will just light up the tires. No wheelies cause the weight is too far forward. The diff slipping is most noticeable when its taking off from a stop. I turned down the punch and starting power almost all the way so it's gentle, but still manages to slip.

[Lonestar]

However, even when fully locked down (I know you should never fully tighten it), the diff still slips on full throttle on asphalt. I can hear it chirp/bark. If I have the slipper loose at all, it just slips way too easily. This setup was clearly not designed for the torque of a brushless motor... versus the smooth clutched nitro power.

Something's wrong... the gear diff is still a novelty item in 2wd offroad. Heck, AE still sold the B6 with a ball diff. All this will modern, much ballsier brushless power than yours. Yes, double-disc slippers work better, but still single-disc should work plenty well.

Which fluids have you used (not trying to be smart but trying to help)?

One thing that can help - most slippery diffs I've had started behaving so when the graphite (thrust) grease went in the main balls section... If you pull your diff apart and see that when cleaning the main balls, they are black, then you have your answer.

Again - the original stealth diff should handle a soft brushless like yours no problem. There is something wrong with the way yours is buit, a defective part or the wrong fluid was used at some point.

[cobrakai]

Yeah... it's really weird.

I am going to disassemble it and see if the thrust grease got into the main balls somehow. I am hoping my new carbide diff balls aren't destroyed from what slipping has occurred.

FWIW, I ran it again today on 3S (insane power) and didn't experience any slipping at all, but it has started feeling chunky again. Time to try again.

What are your thoughts on the ceramic balls? I've heard you can crank them down full tight and still feel smooth.

[RC10th]

Hell, I ran a heavily boosted 6.5T in a 2.25 transmission and never had it slip. Something has to be wrong as others have stated.

Did you do the driver in each outdrive and try to spin the gear by hand test?

I've never run ceramic balls but from what I have read are smoother than carbide and more prone to slipping

[cobrakai]

Huh. I'm not sure how many turns my motor is, but I'm not sure why anyone would want to put a more powerful motor in there. An r/c speed calculator shows it will do 73mph assuming no load. I was only able to get to about 50 today and it was still pulling hard lol while spinning the tires.

I guess ceramic is out if it is even more likely to slip haha. I wonder if buying a set of chrome steel bearing balls (1000 for $8) would be best, and just replace them more often.

[RC10th]

Chrome steel balls are too soft and will flat spot from just sitting under pressure from the diff spring. Pick up a set of AE carbide balls, they are cheap now (used to be $12) and they will last you a long time.

[cobrakai]

One has to wonder... if the steel balls will flat spot, how do the diff rings not squish into nothingness?

[jwscab]

The diff rings are quite hard but will gall and groove when the balls slip. The balls flat spot because there is lots of pressure on a single point of the ball, actually two points directly opposite so it's easy for that too happen.

Go with the b4 clutch and also, if you boosting that motor, turn it down at least on the initial punch .