what causes my spur to be swiggly?

[BrianG]

Yes, the spur is attached to the input shaft. When it is spinning, does the shaft wobble at all?

If the Rustler VXL is anything like the Slash (and I believe it is), the spur is held on with 3 screws. If you screw them in fully one at a time, it can cause the spur to be uneven. I usually put the spur on, tighten each screw finger tight. Then, in rotation, I screw each in a 1/2 turn until done.

Could also be the spring. Not much you can do about that though. How much is the wobble? My Slash spur deviates about 1/2mm as it spins, which is no big deal.