It's not to bad as long as you are in the "normal" driving range. I have exploded a clutch disk before by down shifting. When down shifting, the clutch is disengaged and the clutch disk is speed up by the transmission when you down shift. You can over speed the disk and it comes apart. When up shifting the disk slows down when shifting. This is caused by the taper of the blocking rings of the synchronizer. The synchronizing parts are made of several parts. The gear, synchronizing hub, synchronizing blocking rings, and the synchronizer ring. When shifted the ring slides on the hub and puts pressure on the brass blocking ring. When pressure is applied to the blocking ring, the tapered part of the blocking ring puts pressure on the gear taper. When this happens the synchronizer hub and sliding ring is speed up or slowed depending on the gear selection direction. Once the gear and hub reach the same RPM or close to, then you are allowed to fully slide the hub on to the gear, making the mechanical connection. The gears them self do not move on the shaft only the hub. Simple hu?