Man I had very similar problem. Outcast was running great. Was doing standing back flips all day long and then started hearing clicking noises.
So i figured it was time to service diffs. Pulled out all 3 and was expecting something wrong with them internally but they seemed fine. Refilled with fresh fluid and reinstalled and still same issues. Weird Noises and also underpowered. Was barely able to wheelie and forget about doing any flips.
I was convinced it had sounded like it was coming from rear diff or maybe center but even after replacing the entire rear diff housing I was still having same problem.
Finally decided to just go ahead and replace the one thing left, the front diff housing and it solved my problem. In the Front diff housing one of the four screws holding the diff housing cover on was completely stripped and the others were pretty chewed up. I think this was causing the front diff to become unseated in the housing and causing it to grind against the front imput gear.
It’s kinda a pain to replace the front diff housing since it’s got all the steering components up there but once I did I was happy and relieved to be bashing hard once again.
Good luck man.
