I have the exact same problem...

I've had my b44.1 for about 2 months and I'm about to rebuild the diff for the 3rd time. I called Team Associates to ask about it and they said it's normal. The guy I talked to actually told me he rebuilds both his diffs before each day at the track.

I'm not racing yet, just rallying in my friend's back yard. I don't think I've gone a full day without something on the b44.1 breaking, but usually it's something simple like the front arms.

I've tried shimming following a few tutorials and making sure everything is really tight. The plastic that the bevel gear is made of seems so cheap. Perhaps these metal gears are the solution...except they're out of stock.