X10 mods ?

[andys]

Noticed on an X10 'for-sale' ad it mentioned a bearing mod and a prop shaft spring mod ?

What are these, do I need them, should I have them on my X10 ?
I remember hearing about a bearing mod somewhere near the spur gear on early cars to stop the spur from stripping, not sure how to do it, or if I need it.

Also I could do with some new Diff / Thrust balls, anyone know where to get some (and which ones) for sensible money, rather than getting the TTech ones ?

Northy ???