[maxxdude1234]

I've managed to solve the problem now. The spider gear shaft is very very hard stainless steel - so other than a diamond or tunsgten carbide tipped tool, the only thing I found hard enough to wear it down was......concrete!!!

My problem was that the diff cups were not machined accurately, and did not allow enough clearance for the spider gear shaft to fit in the cup....and the only way I could find to file the very hard shaft to a shorter length was by holding it tightly in a pair or pliers and filing on the my concrete patio!!! how dumb does that sound. Anyway, I managed to take enough material off to fit the shaft in the cups.

If you look at the maximizer cups in the photo the 2 slots are square, but on the fastlane cups they are rounded...stopping the square ended spider shaft from getting in the cup. Hope you understand what I'm saying...

To me this looks like a major design fault with the FLM diff cups. Either that, or severe slacking from the quality control department.....and I hope this isn't true of all their products...