Thanks mark - yes i think it was an AP sure track?
I have never heard the rattling before - it only seemed to happen when the wheels started spinning fast, which I assume was due to the diff locking...
If it does it every time it locks up, i must not have heard it as this would only occur on track, and then I have engine noise and helmet on?
hmmm never heard it when donutting, e.g. dunsfold....
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my mind is blank....