Well i think all the HL gearboxes are the same.... Funny thing is on some of my tanks i can turn the drive wheel and the gear box seems to turn easy and keep spinning and on other tanks well it's very hard to turn the drive sprocket and it don't spin easy at all........ So my next conclusion is the gear boxes with the black motors have stronger motor magnets making them harder to turn where as the white capped motors have weaker magnets making them easy to turn???
Do not know this for sure but it is puzzeling for sure.
And i don't know what it is..