R72 gearbox rebuild help

   Hi. I'm rebuilding my r72 box at the moment. All I'd going well except I'm having issues with the 2nd gear synchro ring. The part number I have used is 24431-63B20, this is what the parts diagram indicates as being correct.  The problem I'm having is the ring fits extremely loose on the 2nd gear itself, exceeding the minimum spec of .5mm gap. The ring I have been supplied looks correct to the pics and 2nd gear doesn't look overly warn. Is it likely that 2nd gear is warn or is do I possible have the incorrect part. ? I have ordered a new second gear just incase but for this to be warn like this seems unlikely Anyone Have any ideas?  

That isn't right.
The syncho has an internal taper that jams onto the taper sticking out of  the gear and brakes/drives it to almost the same speed so the hub outer ring can slip over the teeth of the synchro onto the dog teeth on the gear  and then lock it to the shaft. (well, lock it to the fixed inner part of the synchro hub, which is splined to the shaft.)

Basically, the gear pushes inside the synchro and goes tight before the dog teeth touch - the 0.5mm minimum gap is between the dog teeth on the gear and dogteeth on the synchro when you push them together- you can just look at it or try and rattle a 0.5mm feeler gauge in the gap if it is close.

(As the synchro wears that clearance gets less, when it hits zero the synchro friction faces on the taper can't grip)


There is no way that the synchro can have radial play when it is on the gear, the taper must be miles too big for the gear.