I was driving my ET48 on some grass and doing wheelies and small jumps when I heard a crunch, and then saw that there was no center diff action at all.

When I opened up the diff, I saw this. If you look carefully, you will see that the cross pins holding the spider gears
are all shifted away from the grooves where they belong. The gears are no longer centered between the screw holes. As it stands, the assembly is almost welded together. I can’t get it
apart and my next step is to cut the diff case. The gears don’t look
broken though:
https://cimg0.ibsrv.net/gimg/www.rct...ff36f8b14.jpeg
I was running 80k diff oil which is obviously pretty thick but nowhere near locked. What caused the pins to rip out of their grooves and what is the best way to prevent this from happening again?

The day this happened was a “light” day in terms of bashing. No flips, very small jumps, etc.

Thanks all!

- yes, I drained fluid to see what was wrong, so the pic shows a half empty diff

- in terms of age, the entire diff was brand new as of about a month ago and had maybe 15 battery packs run through it (6s 4500mah, extra long can motor - TP4050 motor).

- I did use grease and seal everything as well as I could. I assembled it per the manual and was pretty careful. The day it died, I still had plenty of resistance and was able to pull wheelies.



- Bill I like the skewer method - will see if I can get that to work next time

- bearings seem ok - spinning freely

- temps are a smidge higher than I like. I have a heat gun and use it often, currently temps are 170ish with the smallest pinion I can fit (15t)

- tires are large and heavy and do have high traction:
https://www.horizonhobby.com/DYNW004...SABEgIso_D_BwE

- surface is grass, which is surprisingly high-traction. It would be safe to say there were plenty of landings that brought all four tires down on the grass pretty hard, resulting in stress on the entire drivetrain

- I think the diff case was ok - it was only a month or two old.

With all that said, I don’t have the space or the skills to really put the ET48 through the sort of stuff you see on YouTube, so it doesn’t seem like I am anywhere near any real edges of durability.

Oh, in case it helps, this is all for a general bashing use case. I don’t have any tracks near me.

In my opinion you need much thicker diff fluid in the center if you’re running an insane motor on 6s. You’re melting the center cup plastic because there’s too much diff action. 80k is super thin for such power. I run 1 million in the center with my TP motors on 6s.....and it’s nowhere near locked still

Thanks for all this great advice!!

Less power is not an option. In fact this motor is my “training wheels” motor while I slowly work my way up to Overkill / Chainsaw levels (easily several thousand more watts)

My basic goals are being able to run 2 battery packs back to back without going over 175 degrees, with 6.5” tires and a top speed of about 65mph on medium length grass. I have most of the above already, except for being able to run multiple packs. Still need to grind down my motor mount so I can get below a 15t pinion (13 might be just right).

I am waiting for the m2c diff case to be in stock and then I will try that.

For now I think I will up the diff fluid to about 300k and keep increasing until the diff doesn’t overheat.

Anyway thanks for the advice - very helpful.

300k fluid in the center diff. So far so good. Excellent traction and still not an uncontrollable wheelie machine.

500k and 1m are on order for further testing. It is great that center diffs with different fluid can be swapped in 2-3 minutes. Allows comparisons within a single session.

Good advice from everyone here - thanks!

Next up is deciding what weight fluid to put in the front and rear diffs. Right now I have the stock weights. I think I will try 80k up front and 50k in the rear.