1015 gears left and right....i used to run them without problems.....but then they started to go south...for me and Multiple of my buddy's....i cant count how many 1015's ive rebuilt to only have fail again and again.....the 1313 issue was with the top case....the center pin retainer didnt have any reinforcement on it and would break...causing the servo to go Crazy tring to center itself....Ace fixed that Long time ago....i still run 1015's...but not in my race rigs....i do know some guys a little south of my that run the AE branded one's with no problem's...but the fact remain's......ive seen Way too many fail to even think on trusting them again....when a 1015 fails's and a 5955 dosent...what else am i supposed to think......the Ace motor's are good.....ive only personally seen a couple have electronic issues....most of the time its the gear's.