I have the 18SS with all the hardened crap. The diff gears simply could not be blown as I have around 10 runs on the car. Also, the bevel gears were properly shimmed with little to zero slop.

The diff gears are the cut type, not the cast. I don't know if the RTR's are cut or cast.

It'll still run for a while though. I'm thinking that even properly shimmed, the diff gear still pushes to the side because of the plastic tranny case.

I suppose I'll crack it open to find out. The diffs are o-ringed, siliconed and sealed, so I hope its not them.