RE: RC8T Diff Problem HELP
If the gears are really that badly worn, you should be able to see it fairly easily. Instead of just refilling, take everything apart in that diff and clean all the parts of the oil. Inspect the gears for wear (you should be able to see if the teeth are worn away) and also the diff case. If the large gear is sitting too deep, that may be a reason why it seems stuck. If it ran dry (with no grease or oil), that would make a lot of friction and heat which could melt or warp the diff case (I've seen this in other diff cases...never on AE though) which would not allow the gears to mesh right nor allow the large gear that's inset too much into the diff case to spin properly. The o-ring on the outdrive won't affect the way your diff spins. It just helps to keep dirt out.