@tmoon---
I noticed during both of those videos, that there is a strange sound coming from either the transmission, slipper, motor, or the diffs. It almost sounds like there are teeth missing from a gear somewhere. I personally have only trashed the rear diff once quite a long time ago. I carefully rebuilt it, shimming where necessary, and have not had any problems with it. The front was torn apart since I was doing a rebuild at the time, and showed no issues, so it was just re-lubed and put back together. All the driving has been on 4S, but will soon see 5S and 6S once my 3S batteries come in. I'll keep ya posted as to how they hold up with the additional power. In the meantime, keep on bashing!