[blykins]

The blocking rings are new....that's what they replaced. The gear teeth look nice and sharp....but the synchro hub teeth look pretty bad. They should be sharp and pointy also...Some of them look blunt.

When you move the shifter fork, it moves the outer hub over the inner hub....There are springs between the outer and inner hubs that aid in pushing the synchronizer keys out. When the outer hub moves out, the outer hub teeth engage the blocking ring teeth. At the same time, the synchro keys are pushing the blocking ring up against the "clutch" cone area of the gear itself....synchronizing the speeds of all assemblies. Then the outer synchro hub can move in further and engage the teeth on the gear itself.

If all of these teeth are not sharp, or there is a problem with the springs, all of these assemblies will not engage correctly....and when the engine is "coasting" it gives it all a chance to fall back apart.