Rear axle/diff has gone...

[Skyracer]

It was easy to remove the axles. 4 screws.


One little pull and they slided out.


With the pinion in place in the axle-house there seem to be NO movement in sideways of the bearings, so I really cant determine wether there is something wrong with the bearings. They seem to be tight and sliding well.

However the ring is slightly damaged.


BUT the pinion is grinded down to thin sharp razor-blades.



So, now is the question, what do I do now?

1. Buy new bearings (doesnt cost much) even though they seem fine?
2. Buy new pinion?
3. Buy new final gear kit (expensive!!!)?

I dont know what caused this, and dont really want to buy parts if something else is causing this. But there are really no other parts back there can be the problem?

Regards
Håkan