I recently had a problem with my spur gear for the TT. My tail had a really weird kick to it, we couldn't figure it out then all of a sudden GAK. I successfully auto'ed it down and found that about 6 teeth were broken off the 54 tooth spur gear. When I built it the mesh between the 54 and 12 tooth spur gear was on the tight side and I though it would just break in but no go. Anyways, got the new parts, put them in and these were tight also. What I did was loosen up all the screws that hold the main shaft bearing blocks in place, loosen the screws that hold the TT tranny in place, then folded a piece of paper in half and ran it in between the two gears and left it there while I re tightened everything. Now the mesh is perfect with just a tiny bit of play between the gears. The tolerances are pretty much perfect on this heli but there is a tiny bit of movement in the holes in the frames where all the screws go through.
I hope the tight mesh was the cause of my tail jerking around which makes sense.
One other thing I noticed when taking apart was the Jesus bolt had a slight S bend in it. I have no idea why? The only thing I can think of is I was doing some hard climb outs trying to get the tail figured out but that shouldn't bend the bolt or is it possible?
I just thought I would post this if anyone else was having trouble with their mesh.