I have no experience with modern gear diffs so can't comment on actual experience. I do have concerns though which may or may not be issues. My concern is temperature change within the diff. Oil viscosity changes with temperature. As the diff heats up, the oil viscosity should get lower. It would be different on different days as well such as winter vs summer running. Then again shock oils suffer from this problem too. The downfall of the old Losi hydradrive was that as battery tech allowed longer and longer runtimes, the hydradrive became less and less useful due to overheat. It would seem that this should hold true in an oil filled diff too. Is this not the case? Does performance change with time?