Funny that Fred and I were both thinking of the same live axel example and apparently came to different conclusions based on our observations at the tracks we run. I was thinking of the inside rear tire slippage (because of the shorter inside turning radius) with a live axel losing traction in a turn, especially on tight turns on low grip dirt surfaces (my off road experience). I have limited experience with dirt off road and oil-filled diffs, but the elite 1/12th scale on roaders I know spend about the same amount of time building their ball diffs as most of us spend building our entire car. I try to build the rear diff as free as possible to help keep the back end planted in a turn and make the car steer with other adjustments. Just the way I do it from years of oval and on-road racing. A few weeks ago I was in Virginia and my B4.2 with an oil filled gear dif (I know most people run a ball diff but adjusting the slipper clutch and the ball diff is one adjustment too many for this old racer) was pushing like a pig on a very (almost uber like) high grip track at Debbie's RC World. I changed a lot of things that week but I never thought of putting heaver oil in the diff - we are all slaves to our past!