[M.D. Holloway]

If the car/truck wants to move when idling and the brakes are preventing that movement, then there is a certain amount of strain on the brakes. The slippage in the torque converter and the attendant heat generated is the result of the engine side of the torque converter moving and the transmission side not moving.

When you move the shift lever from here to there, all that you move is a plate with a mountain of grooves and passageways machine in to it to direct fluid flow where desired. You do not move any gears or synchronizers at all.

You achieve the higher RPM’s in neutral because there is less drag on the engine. That drag is generated by the torque converter sitting there and transmitting no torque.